Tip to 6-speed wiring woes

[rider384]

I swapped in an 01e and in my haste I swapped over the entire engine harness while it was out. I now find that the interior connectors (Connections below the ECU) are different. Is there something I can do to fix this besides pulling the entire wiring harness again? Does it require the engine to be out?

Thanks.

[Scotty@Advanced]

I swapped in an 01e and in my haste I swapped over the entire engine harness while it was out. I now find that the interior connectors (Connections below the ECU) are different. Is there something I can do to fix this besides pulling the entire wiring harness again? Does it require the engine to be out?

Thanks.

You don't have to pull the engine to pull the harness, and you don't have to pull the harness to change those connectors. I suspect that you didn't use the same model year as the connectors are the same for the different transmission types.. Sounds like you need to do some re-wiring!

[8520]

What Scotty said.

[01 A6 2.7]

I wish I had the balls to do this swap...just picked up code P1624 and from the research I've done it's cheaper to swap (diy of course) than to fix the tip...but I'm a carpenter not a mechanic so I'll be stuck wit tip

[Vinchenzo51]

Your solution is actually very simple (since I did it myself).

My car came with a BEL motor, but I used an APB motor so obviously the APB harness doesn't plug into my ecu box connections. So I picked up a 6MT BEL wiring harness (from Byan @ audis4parts.com) and used the 6MT BEL harness on my APB motor. I kept my BEL valve covers so I didn't need to cut and splice the connectors for the coils. I kept my BEL 02 sensors and BEL knock sensors so I didn't need to cut those connectors either. Very simple actually, just swap the parts from the APB to the BEL (or BEL to APB if thats your case) that are easy to swap. If you come across a connection that isn't easily swapped, then cut and replace the connector with the right one.

I think all in all, i cut and swapped 6 connectors total. Maybe less, but it wasn't as bad as I thought.


/rambling

[rider384]

Thanks for the help guys; I did have to re-pin the o2 sensors, so I guess I'll just do that for these as well.

[Audimuscle]

that is the best way I did same :)

[AudiA4_20T]

Your solution is actually very simple (since I did it myself).

My car came with a BEL motor, but I used an APB motor so obviously the APB harness doesn't plug into my ecu box connections. So I picked up a 6MT BEL wiring harness (from Byan @ audis4parts.com) and used the 6MT BEL harness on my APB motor. I kept my BEL valve covers so I didn't need to cut and splice the connectors for the coils. I kept my BEL 02 sensors and BEL knock sensors so I didn't need to cut those connectors either. Very simple actually, just swap the parts from the APB to the BEL (or BEL to APB if thats your case) that are easy to swap. If you come across a connection that isn't easily swapped, then cut and replace the connector with the right one.

I think all in all, i cut and swapped 6 connectors total. Maybe less, but it wasn't as bad as I thought.


/rambling

What's different about the BEL 02 sensors?

[Vinchenzo51]

What's different about the BEL 02 sensors?

I think 4 wire vs 3 wire iirc

[rider384]

Ok, so I swapped the interior connectors that were different (The ones under the ECU) and I have no brake lights. Everything else works.

BTW, since this thread was started the car fired up and ran to temp for the first time, and it did just fine.

I haven't wired in the clutch switch yet, I simply jumped relay left of 267 (As per instructions sent with the swap kit) to start the car and make sure it ran and didn't leak. There's an extra wire coming out of my harness (Engine side, red/green) that matches one of the CPP wires. The old connector under the ECU had one, but the new one does not. I'm going to run a strait wire to it to see if that'll make it work. It has to be wired in anyways.

Any input is hugely appreciated.

[Vinchenzo51]

Ok, so I swapped the interior connectors that were different (The ones under the ECU) and I have no brake lights. Everything else works.

BTW, since this thread was started the car fired up and ran to temp for the first time, and it did just fine.

I haven't wired in the clutch switch yet, I simply jumped relay left of 267 (As per instructions sent with the swap kit) to start the car and make sure it ran and didn't leak. There's an extra wire coming out of my harness (Engine side, red/green) that matches one of the CPP wires. The old connector under the ECU had one, but the new one does not. I'm going to run a strait wire to it to see if that'll make it work. It has to be wired in anyways.

Any input is hugely appreciated.

Did you connect the brake switch? Its completely different from the auto to manual pedal assembly.

I've had my swap done for over a year and still never wired my clutch switch properly. I can start the car without it pushed it, actually quite convenient. I got used to parking in neutral with the ebrake so i've never had an issue.

Not sure about the extra wire. So im no help there.

[8520]

I bypass the clutch switch on all of my cars. I hate them.

[rider384]

Alright, thanks for the help. Confirmed from the wiring diagrams that the wire comes from the ECU and goes to the CPP. Other one is just spliced into the #3 spot of the brake switch. I'm not planning on wiring in the ignition clutch switch... I like being able to start it without pushing the clutch in. I had my old Miata wired that way.

I'll wire in the brake switch tonight or tomorrow and see if the new one works.

[rider384]

New switch is wired in along with the CPP and there's still nothing... the lights do work, when I turn on the parking lights the tails light up, but still no brake lights.

Do the plugs I rewired under the ECU have anything to do with the brakes? I wouldn't think so because of color differences... the other ones were color matched. I checked the brake fuse and it's fine.

I have no idea what it could be.

EDIT: Checked the switch -> ECU connection and it is indeed connected and secure under the ECU. Could the auto-programmed ECU be the cause of the problems? Keep in mind that the stock switch also didn't work.

[Vinchenzo51]

New switch is wired in along with the CPP and there's still nothing... the lights do work, when I turn on the parking lights the tails light up, but still no brake lights.

Do the plugs I rewired under the ECU have anything to do with the brakes? I wouldn't think so because of color differences... the other ones were color matched. I checked the brake fuse and it's fine.

I have no idea what it could be.

EDIT: Checked the switch -> ECU connection and it is indeed connected and secure under the ECU. Could the auto-programmed ECU be the cause of the problems? Keep in mind that the stock switch also didn't work.

Auto ECU won't cause your issue. I drove on my auto ecu for a few months and everything worked fine minus the clusterfuck of codes it was throwing.

If the stock switch also didn't work, then you might have another issue other than the switch assuming you wired the switch correctly. Which I think its only two pins and 1 is to ground, so you kind of can't fuck that up.

[rider384]

Ok, solved the issue. Weak connection between two of the wires and I guess the switch has to be installed to work.

Will my reverse lights come back with the reprogramming of the ECU?

[Vinchenzo51]

Ok, solved the issue. Weak connection between two of the wires and I guess the switch has to be installed to work.

Will my reverse lights come back with the reprogramming of the ECU?

Your reverse lights will work if you have the reverse switch wired up in the transmission. One goes to a wire in your ECU box or in the drivers (i think drivers) a-pillar. I think its a blue wire.

[Vinchenzo51]

I suspect that you didn't use the same model year as the connectors are the same for the different transmission types.. Sounds like you need to do some re-wiring!http://www.sticky-language.com/gu.jpg

Huh?

He said he figured everything out, just needs his reverse switch wired up.

From my notes I have, shows "Left A-Pillar Brown connector Pin 8 Blue/Red wire, cut-off old lead and splice-in new wire to Reverse Sensor", other side to ground. But I didn't personally wire that part, I was working on the clutch switch so I can't give any solid advice.

[belittle]

Ok, solved the issue. Weak connection between two of the wires and I guess the switch has to be installed to work.

Will my reverse lights come back with the reprogramming of the ECU?

Reverse lights are independent of the programming in the ecu.

Do note on the Allroad/A6, you need to use a 12v source that activates the rear lights. The S4's need a ground.

[Vinchenzo51]

Reverse lights are independent of the programming in the ecu.

Do note on the Allroad/A6, you need to use a 12v source that activates the rear lights. The S4's need a ground.

Soooooooooooooooo this is interesting Bryan.

Its a 2 pin connector off the trans. 1 pin to the reverse signal to the car (supposedly in the drivers a-pillar) and the other wire to switched 12v... Not ground?

(this is going to make Greg a very happy person if this is true, he has been dealing without reverse lights for a while mostly because I told him to ground out the other wire lol)

[belittle]

Soooooooooooooooo this is interesting Bryan.

Its a 2 pin connector off the trans. 1 pin to the reverse signal to the car (supposedly in the drivers a-pillar) and the other wire to switched 12v... Not ground?

(this is going to make Greg a very happy person if this is true, he has been dealing without reverse lights for a while mostly because I told him to ground out the other wire lol)

Correct-a-mundo! Important detail that isn't outlined very well in places.

Here is a good shot of my wiring on a previous kit we installed, the bundle of connectors is down by the driverside kit panel:

http://tullinconcepts.com/ebaypictures/01012012/8/DSC00941.JPG

[Vinchenzo51]

Well, fuck me.

Bryan, I need to mail you a 6pack.

So can you grab the reverse signal wire in the kick panel down there? Any idea what color combo the wire is? Hard to see in that pic.

[belittle]

Well, fuck me.

Bryan, I need to mail you a 6pack.

So can you grab the reverse signal wire in the kick panel down there? Any idea what color combo the wire is? Hard to see in that pic.

It's a blue/red wire :)

[jbain2]

I know this is a crazy old thread, but I just picked up a 6mt swapped C5 and the reverse lights are not working. I suspect they weren't wired when the swap was done. I am digging into this now. I have seen a couple of different ways of doing this but am not sure what the best approach is? It seems that you can create a wiring harness that goes direct from the reverse harness on the manual trans to the tiptronic connector? Why are folks not just doing that? But rather running wiring into the ECU or inside the car to the footwell? Thanks.

[blairdude]

I know this is a crazy old thread, but I just picked up a 6mt swapped C5 and the reverse lights are working. I suspect they weren't wired when the swap was done. I am digging into this now. I have seen a couple of different ways of doing this but am not sure what the best approach is? It seems that you can create a wiring harness that goes direct from the reverse harness on the manual trans to the tiptronic connector? Why are folks not just doing that? But rather running wiring into the ECU or inside the car to the footwell? Thanks.

I agree it's WAY easier to modify the auto harness than to swap to an actual manual harness. A harness from the tip connector to the reverse switch is the way to go.

[SteveKen]

Are you able to look down behind the engine to see if there is even a plug attached to the switch? If so, then you need to verify whether it was added on to the automatic engine harness or whether your swap was done with a manual engine harness. I suspect the former.

In the automatic C5 cars, there should be power running to one of the plenum plugs to supply 12V to the lights via the switch. I remember this is a black/blue wire but off the top of my head, I can't cite the exact color plug and pin position number. What does not exist is the rest of the circuit that comes back into the car and feeds the lights and there are a few places where you can tap into this. I do it at the driver's footwell on a blue/red wire and the rest of the details escape me at this time. If you need to add wire, you need to ensure that you use a heavy enough gauge as this is the power used for the lights circuit and it's not feeding a relay.


Also some other tests:

--Put the car in neutral and see if you can start the car without pressing in the clutch pedal. If so, that's strike 2.

--If you have VAGCOM, check the measuring block (I think it's 066) to see if the pedal position changes in the ECU. If not, strike 3.

Reverse, starter interlock and the pedal switch to pin 39 of the ECU are the necessary wiring for a manual conversion.

Not having reverse is a safety issue and probably illegal where your car will not pass a safety inspection
Bypassing the Starter interlock is really dangerous
The pin 39 issue will make the car run poorly since the ECU has no clue whether your shifting or not.


Good luck in your troubleshooting.

[blairdude]

Are you able to look down behind the engine to see if there is even a plug attached to the switch? If so, then you need to verify whether it was added on to the automatic engine harness or whether your swap was done with a manual engine harness. I suspect the former.

In the automatic C5 cars, there should be power running to one of the plenum plugs to supply 12V to the lights via the switch. I remember this is a black/blue wire but off the top of my head, I can't cite the exact color plug and pin position number. What does not exist is the rest of the circuit that comes back into the car and feeds the lights and there are a few places where you can tap into this. I do it at the driver's footwell on a blue/red wire and the rest of the details escape me at this time. If you need to add wire, you need to ensure that you use a heavy enough gauge as this is the power used for the lights circuit and it's not feeding a relay.


Also some other tests:

--Put the car in neutral and see if you can start the car without pressing in the clutch pedal. If so, that's strike 2.

--If you have VAGCOM, check the measuring block (I think it's 066) to see if the pedal position changes in the ECU. If not, strike 3.

Reverse, starter interlock and the pedal switch to pin 39 of the ECU are the necessary wiring for a manual conversion.

Not having reverse is a safety issue and probably illegal where your car will not pass a safety inspection
Bypassing the Starter interlock is really dangerous
The pin 39 issue will make the car run poorly since the ECU has no clue whether your shifting or not.


Good luck in your troubleshooting.

Getting reverse lights working on a manual swap is as simple as making a jumper harness from the transmission range sensor connector in the engine bay to the reverse switch. BOTH wires are accessible there (IGN+ and reverse output).

Starter interlock is not really a safety issue IMO. It makes starting fool-proof, but probably if you're converting a car from auto to manual you're not a fool. Here In Canada they weren't even required until at least the 90s. My 91 240sx didn't have one from the factory even though US market cars had them.

[jbain2]

Getting reverse lights working on a manual swap is as simple as making a jumper harness from the transmission range sensor connector in the engine bay to the reverse switch. BOTH wires are accessible there (IGN+ and reverse output).

Starter interlock is not really a safety issue IMO. It makes starting fool-proof, but probably if you're converting a car from auto to manual you're not a fool. Here In Canada they weren't even required until at least the 90s. My 91 240sx didn't have one from the factory even though US market cars had them.

On the reverse connector do you know which pin is the reverse? My understanding is that the other is 12v+?

Thanks.


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[blairdude]

On the reverse connector do you know which pin is the reverse? My understanding is that the other is 12v+?

Thanks.


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The reverse switch literally just completes a circuit. It doesn't matter which one has constant 12V. When the switch is engaged, it sends 12V from one pin to the other.

[jbain2]

Is there a way to confirm in measuring blocks if the reverse lights are getting a signal? It looks like the reverse connector is actually wired from my transmission to the wiring harness behind the motor. I also can not start the car without the clutch depressed and it gives me the message on my cluster to start car depress clutch.


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[blairdude]

Is there a way to confirm in measuring blocks if the reverse lights are getting a signal? It looks like the reverse connector is actually wired from my transmission to the wiring harness behind the motor. I also can not start the car without the clutch depressed and it gives me the message on my cluster to start car depress clutch.


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The reverse switch status won't be found in any of the measuring blocks even when wired exactly like stock. You'll have to start probing wires with a multimeter. You can also check for continuity between the pins right on the switch (with the shifter in reverse) to verify that the switch is working correctly.

[jbain2]

The reverse switch status won't be found in any of the measuring blocks even when wired exactly like stock. You'll have to start probing wires with a multimeter. You can also check for continuity between the pins right on the switch (with the shifter in reverse) to verify that the switch is working correctly.

Where does the wiring come into the ECU? Plug and wire? Sounds like I need to verify that it’s also in the kick panel?

Thanks for the replies.


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[blairdude]

Where does the wiring come into the ECU? Plug and wire? Sounds like I need to verify that it’s also in the kick panel?

Thanks for the replies.


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It's not wired to the ECU

[jbain2]

It's not wired to the ECU

From the B5 threads it appears that it is.
Tan connector terminal 5 with blue/black wire
Red/Oragne connector terminal 1 with blue/brown wire

Is this different for the C5? Just trying to get as much info as I can before I dig into this tomorrow.

[blairdude]

Black/blue wire should just be switched ignition, nothing changes on that wire besides current flow whether or not reverse switch is engaged. Likely wired to other circuits not directly related to reverse lights. Blue/red wire (in C5) goes to Park aid 16 pin brown connector pin #6, Park/neutral relay (auto harness) pin #5, transmission range switch (auto harness) pin #8, reverse switch (manual harness) pin #2. Also to the trailer socket, pin #8. Nothing to the ECU.

[jbain2]

Black/blue wire should just be switched ignition, nothing changes on that wire besides current flow whether or not reverse switch is engaged. Likely wired to other circuits not directly related to reverse lights. Blue/red wire (in C5) goes to Park aid 16 pin brown connector pin #6, Park/neutral relay (auto harness) pin #5, transmission range switch (auto harness) pin #8, reverse switch (manual harness) pin #2. Also to the trailer socket, pin #8. Nothing to the ECU.

Thanks. So slightly different. I’m hoping to open up the ECU housing with the connection’s tomorrow. Getting to the reverse switch wiring and checking for continuity will be a little tougher for me as I don’t have a garage and the vehicle is in the street.


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[rollerton]

Well-- I will tell you how I did it a few times, at least the first time. After that I think I had remembered what color the wires were in the harness. Go crawl under there and get to the big fat connector that came off the auto trans. Grab a test light and turn the key on, probe the contacts until you find one with power when key is on, no power when key is off.
Now, jam one end of wire in there and jump the other end to each of the other contacts in the connector one at a time until the reverse lights come on; then jump those two wires to the reverse switch. You're done.
AFAIK There is no danger of damaging anything from jumping V+ in that harness, once the trans and TCU are gone no circuits in that connector go anywhere that matters; they're just extra wires.

[jbain2]

After doing some digging, the swap was definitely done with a manual harness. I can see the transmission connector coming off just above the drivers side front axle and coming up along the bell housing to join the harness. I haven't had a chance to pull the kick panel yet, but I'm guessing that the wiring described above isn't there as this was originally a tiptronic car. Will take a look and report back.

[SteveKen]

After doing some digging, the swap was definitely done with a manual harness. I can see the transmission connector coming off just above the drivers side front axle and coming up along the bell housing to join the harness. I haven't had a chance to pull the kick panel yet, but I'm guessing that the wiring described above isn't there as this was originally a tiptronic car. Will take a look and report back.

I think you are looking at the vehicle speed sensor plug if you are looking at the driver's side. Located circled in pink below.

The reverse switch is on the other side. Circled below in red.

https://onedrive.live.com/embed?resid=2EE561B6DE325D20%212647&authkey=%21AExKYhOuQrcEt1M&width=1024

[jbain2]

I think you are looking at the vehicle speed sensor plug if you are looking at the driver's side. Located circled in pink below.

The reverse switch is on the other side. Circled below in red.

https://onedrive.live.com/embed?resid=2EE561B6DE325D20%212647&authkey=%21AExKYhOuQrcEt1M&width=1024

Really? From the other threads I've seen, they indicate it's on the drivers side? It says its just above the VSS. The connector I see is the flat 5 pin connector style referenced in the thread below.

https://www.audizine.com/forum/showthread.php/443259-*DIY*-Making-your-REVERSE-lights-work-after-a-5-speed-swap

I have a 6 speed 01e, the thread above if referencing a 5 speed, but I am assuming they are the same.

[SteveKen]

I have a 6 speed 01e, the thread above if referencing a 5 speed, but I am assuming they are the same.

I'm not sure what's goin on in that thread, but the VSS location and the reverse switch are all the same for the 01E 5 and 6 speeds. The wiring from them may be different.

If you have a manual engine harness, the reverse switch should:

---get power at T10f/5 (brown connector behind the ECU) the wire color on both sides of the connector is black/blue
---return to the lights through T17k/15 (red connector behind the ECU) the wire color on both sides of the connector is blue/red

If reverse doesn't complete the circuit at these two pins, then you have a bad switch or wiring issues.

If these 2 pins do not exist, then your have an automatic harness.

[jbain2]

I'm not sure what's goin on in that thread, but the VSS location and the reverse switch are all the same for the 01E 5 and 6 speeds. The wiring from them may be different.

If you have a manual engine harness, the reverse switch should:

---get power at T10f/5 (brown connector behind the ECU) the wire color on both sides of the connector is black/blue
---return to the lights through T17k/15 (red connector behind the ECU) the wire color on both sides of the connector is blue/red

If reverse doesn't complete the circuit at these two pins, then you have a bad switch or wiring issues.

If these 2 pins do not exist, then your have an automatic harness.

Thanks.

It appears the PO used a manual harness. Here’s what I have going into the ECU plenum box.

https://uploads.tapatalk-cdn.com/20240828/bad66167bd40602bb6719c21f3a4ec39.jpghttps://uploads.tapatalk-cdn.com/20240828/d208e31e757c67f23f0fc166993ccd1b.jpg

Here’s what’s in the kick panel including the remnants of the old auto harness.

New harness
https://uploads.tapatalk-cdn.com/20240828/d0038a2c8641c8d917f9850717949363.jpghttps://uploads.tapatalk-cdn.com/20240828/b011141646082ad274c234381fee81b4.jpg

Prior harness (wasn’t connected)
https://uploads.tapatalk-cdn.com/20240828/8591a7794d2276de448d5bf8a5606d0d.jpg

Need to confirm that the red/blue wire is to the correct location.

Test continuity and then I guess look at the reverse switch. Outside of just replacing that is there a way to know if the switch is bad?


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[SteveKen]

If you can confirm that you get continuity on the red/blue and black/blue wires of the engine harness when you put it into reverse, then your harness wiring, reverse switch and the reverse mechanism inside the transmission are proper.

Then can you look a the mating connectors behind the ecu and see if any mating pins exist? The black/blue one in the brown connector should be there as it's on all cars regardless of auto/manual.

If it's there, and the blue/red on the red connector is not there, then you need to get the blue/red/wire from the engine harness connected to this wire in the driver's kick panel:
https://1drv.ms/i/s!AiBdMt62YeUulF6c-xtzBEdBDOTA?embed=1&height=1024

I'm not sure what all that other wire mess is, so hopefully that's nothing major. The brown one with cut wires is a 17 pin connector and the one you should be concerned with is a 10 pin connector.

[jbain2]

Well, I have continuity from the switch wiring to the ECU plenum box and from the plenum box to the kick panel. Must be the switch?


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[jbain2]

So to test continuity with the car in reverse I would put it in reverse and then test is I was getting a signal at the kick panel? Don’t think I’d need to do the plenum box as I know I have continuity from the connector at the switch to the plenum and then from the plenum to the kick panel. Just confirming. Thanks.


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[SteveKen]

So to test continuity with the car in reverse I would put it in reverse and then test is I was getting a signal at the kick panel? Don’t think I’d need to do the plenum box as I know I have continuity from the connector at the switch to the plenum and then from the plenum to the kick panel. Just confirming. Thanks.


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I would check continuity on the engine harness plugs first as it's easier access.

If you do not get any continuity, then it's either the reverse switch, the plug is unplugged or it's wiring somewhere inside the harness between the plugs.

I assume that reverse works and you can move backwards?

Worst case is that the tab on the selector rod inside the transmission is not there. This is what the sensor sees when it's in reverse.

[jbain2]

I would check continuity on the engine harness plugs first as it's easier access.

If you do not get any continuity, then it's either the reverse switch, the plug is unplugged or it's wiring somewhere inside the harness between the plugs.

I assume that reverse works and you can move backwards?

Worst case is that the tab on the selector rod inside the transmission is not there. This is what the sensor sees when it's in reverse.

I have reverse and it functions as it should. I removed the plug from the reverse switch on the transmission. Tested continuity from that to the plug in the ecu plenum and it was good. I also tested continuity from the plug in the plenum box to the wire you highlighted and that was also good. This would lead me to believe that its either the switch or something inside the transmission as you suggested.

[jbain2]

Got a new switch. Hoping to get it installed tomorrow. Also of note, the side view mirror does not dip when I’m parking in reverse and the dial is turned to the passenger side. So clearly the signal is not being communicated.


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[jbain2]

Well. Bad news, bad news. There are in fact three different reverse switches for the 01e apparently. I ordered 2 of them based on what I could see. And of course I need the other style connector and I don’t have any of the female connectors that I could use to make one using the existing wiring.

https://uploads.tapatalk-cdn.com/20240902/3402d74ce172c6b47d3c23d82b26dc18.jpg

Also, tested the existing switch for continuity when depressed and it is in fact in tact. Which means I have another issue somewhere.

Because the existing switch has continuity across the switch. I have continuity from the switch wiring at the transmission to the ECU plenum and I have continuity from the plenum to the kickplate connector.

Not sure where to go from here…?


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[jbain2]

Waiting on the new switch. But I’m assuming that when I get it, I should be able to pop it in the connector which I left disconnected as the car doesn’t care and depress the switch and if it’s going to work the reverse lights should go on?


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[jbain2]

Well, put the new switch in. Didn’t install in the bell housing. Figured I could manually activate the switch by depressing it and get the reverse lights to come on. No dice. I’m at a loss. I have continuity from the switch all the way to the kick plate. The wiring coming out of the kick plate is the blue and red wiring which is consistent with what’s coming in from the ECU plenum.

There are 2 blue/red wires coming out of the kick plate. I don’t know where they actually go.

At this point my assumption is that I have an issue from the kick plate back to the rear housings/bulbs. I know it’s not the bulbs as I changed them and they both still
Look good so I didn’t short them out or anything.

Any other thoughts would be appreciated.

Thanks.


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[ShelbyM3]

Well, put the new switch in. Didn’t install in the bell housing. Figured I could manually activate the switch by depressing it and get the reverse lights to come on. No dice. I’m at a loss. I have continuity from the switch all the way to the kick plate. The wiring coming out of the kick plate is the blue and red wiring which is consistent with what’s coming in from the ECU plenum.

There are 2 blue/red wires coming out of the kick plate. I don’t know where they actually go.

At this point my assumption is that I have an issue from the kick plate back to the rear housings/bulbs. I know it’s not the bulbs as I changed them and they both still
Look good so I didn’t short them out or anything.

Any other thoughts would be appreciated.

Thanks.


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I have no first hand experience with wiring for a swap, but this whole time I’ve always felt that because you’ve got a swapped A6 Avant that that is at the heart of all your issues. Do you know what the A6 came with factory wise? 2.8 or 3.0? That could be a contributing factory to your gremlins. Just trying to help think outside the box. Also, do you know if your cluster was swapped, at all?


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[jbain2]

I have no first hand experience with wiring for a swap, but this whole time I’ve always felt that because you’ve got a swapped A6 Avant that that is at the heart of all your issues. Do you know what the A6 came with factory wise? 2.8 or 3.0? That could be a contributing factory to your gremlins. Just trying to help think outside the box. Also, do you know if your cluster was swapped, at all?


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It was a 3.0 tiptronic. I don’t know if the cluster was swapped. I wouldn’t think there would be a reason to do so.

The wiring from the kick panel out to the car and CCM is the original. There are actually 2 blue/red wires going out of the body plug in the kick panel. I’m assuming that one of them is going to the CCM. Based on the wiring diagram I see, the other wire would be going to the old TCM. But since it’s manual swapped I don’t utilize the TCM. I haven’t verified that it has been in fact removed. I believe it’s under the passenger front carpet? Again, this shouldn’t be in the equation. I’m trying to figure out if it is still would it be influencing what’s happening in any way?


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[blairdude]

It was a 3.0 tiptronic. I don’t know if the cluster was swapped. I wouldn’t think there would be a reason to do so.

The wiring from the kick panel out to the car and CCM is the original. There are actually 2 blue/red wires going out of the body plug in the kick panel. I’m assuming that one of them is going to the CCM. Based on the wiring diagram I see, the other wire would be going to the old TCM. But since it’s manual swapped I don’t utilize the TCM. I haven’t verified that it has been in fact removed. I believe it’s under the passenger front carpet? Again, this shouldn’t be in the equation. I’m trying to figure out if it is still would it be influencing what’s happening in any way?


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Cluster is not connected to the reverse lights circuit at all in any C5 (unless an aftermarket addition like for 3DColorMFD). Neither is the central locking module. Besides the taillights, the reverse signal also goes to the park aid module (for parking sensors), and park/netural relay (auto trans).

[jbain2]

Cluster is not connected to the reverse lights circuit at all in any C5 (unless an aftermarket addition like for 3DColorMFD). Neither is the central locking module. Besides the taillights, the reverse signal also goes to the park aid module (for parking sensors), and park/netural relay (auto trans).

The wiring diagram I have actually indicates the wiring goes from the kick panel to the CCM. From the CCM to the system control module under the drivers side dash. Then back to the light housings. https://uploads.tapatalk-cdn.com/20240909/5a00e1396bfee51858a98aee76f8faa1.jpg


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[jbain2]

So adding follow up. I have confirmed that I have continuity from both wires on the reverse switch. There is one that comes into the ECU plenum to the as the black/blue wire to the tan connector. I have continuity between that connection and the fuse box at 31 where it gets power. The other wire off the switch comes into the ECU plenum as a blue/red wire to the red connector. I have confirmed that I have continuity between that the kick panel, the CCM and the rear housing.

I installed a new switch and manually depressed it before installing into the bell housing. This did not trigger the lights to come on when the car was running. I am at a total loss at this point.

[jbain2]

Admittedly I’m a wiring novice. I drew out a rudimentary diagram of how the wiring is running as confirmed by my continuity testing.

https://www.dropbox.com/scl/fi/2a62jqbu3z38t4w1lgwra/18C1AE35-C071-47C3-9B9C-089486950A25.JPG?rlkey=rip4relii8onvglybipktgvn0&dl=0

Sorry, I can’t upload pics via the app.

I’m having a hard time figuring out what other way I can test the circuit.

I have a multimeter which I have been using for the continuity testing.




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[jbain2]

Follow up on this. Turned out to be a short in the harness segment between the switch and the footwell. Redid the wiring and now I have reverse lights.


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[ShelbyM3]

Very nice! Continuity check with a multimeter or how’d you find it?


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[jbain2]

Very nice! Continuity check with a multimeter or how’d you find it?


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Discovered I was getting power to the signal wire when I shouldn’t have been. Replaced that segment from the switch to the kick panel and all is good. Must have been either a short in that segment or the way it was wired. Honestly it looks correct so I’m thinking a short. The whole thing was slightly strange honestly.


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