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Mad Cow
04-16-2013, 08:54 AM
I finally found the root cause of so many of my ECU issues, the relay stays closed after I turn the car off so the ECU never actually turns off. The odd thing is I can manually move the contact inside the relay back after I turn the car off and it'll stay open until I turn the car back on, just like it should. I've never even heard of this happening before so I'm pretty confused. The only thing I can think of is there's a large capacitor somewhere storing charge and keeping the relay closed. I do have the ECU relay powered off what used to be the SAI pump circuit because the correct wire on the AHA harness is too thin, but the only difference I can see between the 2 circuits is the SAI pump has a fuse and potentially shares its source with more stuff because it connects to the distribution block under the dash. Could it just be a bad relay or am I looking at a wiring issue?

redline380
04-16-2013, 09:04 AM
I do have the ECU relay powered off what used to be the SAI pump circuit because the correct wire on the AHA harness is too thin, but the only difference I can see between the 2 circuits is the SAI pump has a fuse and potentially shares its source with more stuff because it connects to the distribution block under the dash. Could it just be a bad relay or am I looking at a wiring issue?


im no electrical expert but i would happen to think this is playing a large role in your issue. is there another possible spot you could power the relay up? but i would also replace the relay just to rule that out

walky_talky20
04-16-2013, 09:11 AM
I assume we talking about the ECU power supply relay?

In any case, it sounds like you have a wiring issue. That relay has constant 12V+, so power is there - no capacitor needed. (EDIT: Actually, if you are using the original wiring to the SAI relay, power is through the Fuel Pump relay and is not constant). The issue is that the relay coil is finding a path to ground. Anything on the other side of the coil (opposite the 12V+) that is a suitable path to ground will try to keep the relay closed. It may not be able to close it after you pry it open, but it will be enough current through the coil to keep it closed. Put a volt meter across the relay coil and you'll be able to see the problem. See what you get compared to when the key is on.

Is the other side of that relay coil connected to anything other than pin 21 on the ECU?

Mad Cow
04-16-2013, 03:56 PM
According to my wiring diagrams the SAI wiring goes straight to 30 before the fuse, no relays involved and I do get a constant 12v from it. I cut off the wire at the body plug side and routed it to the other connector so basically I bypassed the whole SAI circuit post-fuse. I haven't touched the other side of the relay, just a resistor in place of the VVT tensioner. I'm using an ATW harness but the relay circuit seems to be identical to the AWM. The only odd thing I noticed was that I get around 5v at pin 4 of the brown connector, but that just goes straight to the starter and doesn't even approach the ECU. I'll try holding it closed after unsticking it and seeing if there's some voltage across the coil.

Mad Cow
04-22-2013, 07:10 PM
I'm not really understanding how this relay works, the coil gets a constant 12v and is grounded by the ECU right? For some reason I get 12v at both relay coil connections and pin 21 of the ECU until I turn the key, then I get around 0.9v until I force the relay open. After I open it I can hold it closed and still see 12v. I also noticed that unplugging the large connector open the relay, so I guess the relay itself is fine.

My wiring diagrams also say that the ECU relay pinout is different after '02, and my relay is from a B5.5 Passat (165 906 381, 30) but if I set it up per the diagram it wouldn't work. The only thing out of the ordinary is that it uses the 86a pin instead of 86, which is right according to the wiring diagram. Is there a different relay involved? My ATW harness didn't come with one and I can't find a single ATW in a junkyard, but it seemed to me that the AWM relay would work perfectly fine. ETKA makes no mention of a different relay but I've heard so much talk about the AWM having a different one that I'm not sure.

EDIT: Some further searching showed me that the relay was changed for the B5.5 Passat and B6 (1J0 906 381, 429), but my relay is the older one so it should be fine in that sense.

Mad Cow
04-25-2013, 01:33 PM
Just put in a 429 relay, what a royal PITA that was. Still the same result. I'm fully stumped now, I guess it's time to search for an AWM harness to rule out my frankenstein automatic ATW harness that was already damaged when I got it.

EDIT: This just got a whole lot weirder, the motor randomly shut off at idle not long after I changed the relay, I restarted it and now throttle cut works fine. I still have communication with the ECU with the key out, but now it gets interrupted for a second when I turn the key. [:/]

Mad Cow
05-12-2013, 01:21 PM
I seem to be talking to myself here, but somehow, by some miracle my car is slowly fixing itself. I used to always be able to connect to the ECU no matter how long it's been sitting with the key off, but every once in a while I try to connect and it fails. I turn the car on and off again and it can still connect, leading me to think the relay opens eventually but not instantly. I also have proper throttle cut at least half the time I drive now, so it's doing something right. I've also noticed low RPM throttle response is much better when throttle cut works, and the motor seems to run a bit smoother in general leading me to think that the O2 sensor is finally coming into play. Still no SAI codes though.

Could running a maxi fuse instead of a regular fuse after the relay (fuse 29) have something to do with it? I can't see why it would but it's the only thing I modified in that circuit. Any help in explaining this sorcery?

Mad Cow
06-19-2013, 02:36 PM
Bump again, this issue is driving me insane. Spent the past few hours scouring wiring diagrams and once again can't find a thing. The only modifications I did to the wiring pre-body plugs is tapping into fuse 7 for the black/blue wire that goes to T10ar/4 and the various pedal-related switches; this is exactly how the AWM is wired from the factory. In the main power circuit all I did was run a wire with a resistor from the relay to pin 115 on the ECU for the missing VVT tensioner. I didn't mess with anything in the relay trigger circuit post-relay, all I did was run a wire from one of the 30 posts under the relay panel to T10m/4 for the power input, again just like how it's supposed to be. I used the now-defunct SAI pump fuse in place of fuse 29 to avoid the whole looping back to the body plugs that the stock circuit does. There's one difference I noticed with the fuel pump relay, which is that the 87F/DTI pin powers fuse 29 for the AHA and 32 for AWM, however fuse 32 is powered directly off the ignition switch for AHA so it seems that there shouldn't be any issues there, all it does it power the injectors anyway.

Has anybody dealt with the ECU power supply circuit enough to help me out?

walky_talky20
06-19-2013, 06:26 PM
Maddy (can I call you Maddy?), I got your PM. The reason I bowed out of this thread is because I don't know enough about this circuit. Please see this thread where I got called out for not knowing what the heck I was talking about (guilty as charged):

http://www.audizine.com/forum/showthread.php/528302-Supplying-power-to-an-ECU

There is some general weirdness with how that relay is controlled, and I am not qualified to help you further. Hopefully somebody else will chime in.

The best advice I can give is perhaps you can obtain 12v+ for the relay coil from the 15 circuit instead of the 30 circuit. That way the relay surely cuts out with the key off. That's really a band-aid, but that's all I've got for you.

Mad Cow
06-19-2013, 08:38 PM
Never been called Maddy before, though I did get Displeased Bovine once, that was my favourite. Oddly enough I don't even remember posting in that thread, and reading it now confuses me even more now that I see pin 21 needs to get 12v to power the ECU. I'm going to look into the differences between early and late A6 2.7t's as I see now the later ones got the relay too. If anything I have your solution as a last resort, I actually never considered something so simple.

On another note, I feel kinda proud in a weird way knowing that my problems can't be solved by even walky_talky, I don't think I've ever seen that before (except for that thread).

walky_talky20
06-20-2013, 06:15 AM
lol @ "even walky_talky". I worry that I portray myself as some sort of expert on here, when in fact that is ridiculous and laughable. Sorry I'm not living up to expectations.

Mad Cow
06-20-2013, 07:45 AM
I always say "the more you learn, the more you know you don't know". Every time I go in-depth I realize that I don't know crap about the subject, when I dig deeper I find even more things I don't know, things that I previously didn't even consider or know existed.

un1ko
07-27-2014, 08:58 PM
I always say "the more you learn, the more you know you don't know". Every time I go in-depth I realize that I don't know crap about the subject, when I dig deeper I find even more things I don't know, things that I previously didn't even consider or know existed.

Hey Mad Cow did you ever figure this issue out? Is that I'm running into the same issue.

Mad Cow
07-28-2014, 09:45 AM
To be honest I just gave up. I could get it to work a couple of different ways but each way had weird side effects that became more of a problem than the initial issue. Plus I swapped in a more correct engine harness a while back and haven't had the motivation to start cutting into it, though I might try again later. Plus it doesn't seem to be causing any problem, my issues before were actually from an incomplete ECU flash.

un1ko
07-29-2014, 06:50 AM
To be honest I just gave up. I could get it to work a couple of different ways but each way had weird side effects that became more of a problem than the initial issue. Plus I swapped in a more correct engine harness a while back and haven't had the motivation to start cutting into it, though I might try again later. Plus it doesn't seem to be causing any problem, my issues before were actually from an incomplete ECU flash.

I hear you, this issue is driving me crazy! So I tried bridging a wire between fuse 29 to T3aa/2 and it worked. I was able to have my car run smoothly, I got gas pedal response and I was able to flash my ECU. The only issue I have is when I connect that wire the fuel pump doesn't turn off, when I turn the car off. So since I haven't drove my car over a year and a half, as a temp fix I'm going to add a switch between that wire. So when I turn off the car I'll have to turn the swtch off. It's weird because when I don't connect the wire fuse 29 works fine. 429 relay is a big pain in my a$$! In one of your comments you said of using fuse 32. Did you end up trying it? I'm still going to work on this issue. I'll let you know if I figure it out.

Mad Cow
07-29-2014, 03:02 PM
Have you tried triggering the relay through a separate switched 12v source? I did that at one point and it seemed to work best.

un1ko
08-02-2014, 08:04 AM
Have you tried triggering the relay through a separate switched 12v source? I did that at one point and it seemed to work best.

No that's what I'm going to try now. Since my temp fix, by using a switch and it didn't work. The check engine light turns on. So, since I have an S4 this is what I figured out.


AWM
Fuel Pump - 87F/DTI -> Fuse 232 -> T10ar/5 -> Fuel Injectors

APB
Fuel Pump - 87F/DTI -> Fuse 229 -> T10ar/1 -> Coil Packs


AWM
N205 -> Fuse 204 -> Fuse 229

APB
N205 -> o2 Heat Sensor -> T4z/1 which is the same as T4y/1 (Since 2.7T has two o2 heat sensors)


AWM
Coil Packs -> Fuse 229 -> T10ar/1

APB
Fuel Injectors -> Fuse 232 -> T10ar/5


So based on this I think I need to switch Fuse 232 (T10ar/5) with Fuse 229 (T10ar/1).

freekonwheelz1
07-11-2017, 12:29 PM
To be honest I just gave up. I could get it to work a couple of different ways but each way had weird side effects that became more of a problem than the initial issue. Plus I swapped in a more correct engine harness a while back and haven't had the motivation to start cutting into it, though I might try again later. Plus it doesn't seem to be causing any problem, my issues before were actually from an incomplete ECU flash.

so this relay not functioning as it should was caused by an incomplete flash? im running into the same problems and i just noticed while reading this post that it actually started around the time i unlocked my ECU... ive flashed my car probably half a dozen times now and its done this problem at least once on every single flash. how did you nail down this being involved in your problem? i have to unplug that relay and plug it back in all the time due to it messing up so much. Im debating on making a pigtail to move the relay to an easier spot so when it happens i can just unplug it, plug it in, and be on my way again. I have noticed though that if my car sits a while itll work just fine but if i turned it off 10-15 minutes before and try to restart it (going into a store or anything of the sort) itll fail 100% of the time. only once has it messed up while it was already running and all it did was cut my throttle to make it just idle (which sucked because i was doing 60 on the highway and no matter how much throttle i gave it it was steadily slowing down.)

sorry to bring back a old post though...