4.2L V8 Swapped B5 A4

[KraemerSXED]

This is how my cover looks. I don't even use it though because it restricts to much air flow for the tight engine bay. I mean my motor never ran to hot with it on but I didn't like it.

[lazerreda4]

just got my brothers b5.5 Passat just about done. one last thing is to wire in pin 21 for power. and was wondering what diode you ran on that pin on your setup?

[bhusted]

This is the diode I'm using currently, though I'm not quite happy with it. I've got 2 in series and still get occasional strange shutdown behavior from the ECU. It's a cheap way to get it up and running for now. Make sure you orient the cathode (the side with the line) toward the ECU. To replace the diodes, I'm going to run a 5 pin relay where pin-21 is connected to pin-30 on the relay, 87 is +12v and 87a is ground. I'm hoping that by dumping pin-21 to ground when the ignition is turned off, I can eliminate the shutdown issues.

Edit: Link doesn't appear to work. You can get the diodes at Radio Shack. Part# 276-1661

[lazerreda4]

used that diode and it is working now. but if issues arise we will do the relay mod. thanks for your help

[bhusted]

It's interesting that I got different behavior than you using the same part. Did you use one or two diodes? What source did you use for power?

[lazerreda4]

1 diode. we had a old fuse box laying around out of a jetta. so we pulled a few pinned wires out of it and stuck them in a open fuse port in the Passat fuse box. ran the wire from pin 21 with the diode to one side. then ran a switched power wire to the other side. used a 5amp fuse to connect them. been working so far with no side affects. only been a day though

[bhusted]

Where did you pull your switched power from?

[lazerreda4]

we tapped into fuse 7. have a speedo cluster question were I have the 02 a6 cluster in my car. the dimmer for the cluster is next to the headlight switch and not in the cluster. question is there a way to wire in the dimmer switch? and the fuel gauge is off. is there a way to get that working correctly? only reason I want to keep the a6 cluster is the center display is mint. my original cluster is toast.

[bhusted]

I don't know of any way to keep the dimmer or fix the fuel gauge. This is why I chose to use a 2000+ S4 cluster instead of the A6 cluster. In the mean time you may want to send out your cluster to have the LCD replaced.

[lazerreda4]

I figured was a no go. I will see about getting mine fixed. I will use it until then though

[walky_talky20]

I think VCDS can do some adaptation on the fuel gauge. Not sure if it could get it all the way back, but worth a shot. And the external dimmer should just be a couple wires, right? And then hide the control.

[lazerreda4]

had both clusters apart and the original a4 cluster dimmer looks like it could be soldered on to the a6 board. my soldering skills are weak though. don't want to burn anything up. hahha

[bhusted]

Getting tired of the strange shutdown behavior and decided to work on it today. Previously I had been using two rectifier diodes in series connected to pin 21 at the ECU and getting switched power from fuse #7. When the key is turned off, the engine will stumble and eventually stall. Cutting power to pin 21 causes the engine to shutdown immediately. I decided to "fix" this by installing a SPDT relay inline with the ECU power. A diagram of my work is below.



I figured that having the relay here would simulate cutting power to pin 21. With the new relay the engine won't even shut down. Somehow the ECU is still getting power. Pulling fuse 7 will cause it to shutdown immediately. Anyone have any idea of how/why the ECU is able to keep the ignition from turning off? I thought for sure that this would solve the problem. I don't get it.

[bhusted]

Still working on this. Anyone have any ideas? I've also tried going back to the two diodes and adding a resistor in the line to drop down the voltage to the pin. No difference from just running the two diodes. I'm at a loss here...

[Mad Cow]

This is why I just gave up on 'good enough' with mine, every time I looked into it I just got more confused. I have a feeling it has something to do with the immo, even though it's disabled through software I have a suspicion that the ECU hardware is different enough to cause these weird issues. I'm running an immo ECU at the moment and I'm looking for a cheap non-immo ECU to test my theory, if it works then that will really narrow down the possibilities. It really sucks that there's next to no documentation on how the J271 relay actually works since there's definitely some electrical trickery going on in OEM configuration.

[bhusted]

Do you just live with the constant CEL because of this? I'm fairly certain that a CEL is an instant fail with I go in for emissions testing. The frustrating thing is that I've done exactly what others have done and been successful with and yet it doesn't work for me. What setup are you using to deal with this?

[Mad Cow]

I don't get a CEL, I'll get a code for voltage too low occasionally but that doesn't trip the CEL. I currently have J271 wired in as close to stock AWM spec as I can, I even tapped the same fuse for switched 12v. That's why it's so weird to me, it should work just fine since it's a 100% copy of how it's done from the factory, to my knowledge, and it still doesn't work right.

[bhusted]

Maybe I should try that. There must be some gremlins that live in that relay. Every shutdown I get a slight hesitation, stumble, and beep from the cluster as the engine dies. This throws lots of false codes and is super frustrating.

[rusky04]

One of the ecu power wires runs to this




Move that ecu power wire to another source, it helped me I had similar issue

[bhusted]

Thanks. I'll give that a look tomorrow.

[rusky04]

any updates if it fixed your issue? if not, rewire the other power wire that runs to the ecu, leave the one from above at the source you wired it to . that should do it.

[bhusted]

I've been doing some work on the car in the past couple of weeks. My two year emissions test is due at the end of the month. I still need to work on the ECU power problem with the "stumble" shutdown, but after a lot a thrashing around I've replaced the two downstream O2 sensors. Both were giving me consistent codes, so I bit the bullet and went for it. The passenger side sensor went fine, but the driver side one was heavily corroded and when I removed it, many of the threads from the sensor were left behind in the hole. Much time later with a tap, the second sensor went in.

Now my only codes are:
17070 - ECM Power Relay Control Circuit (J271): Short to GND
P0686 - 35-00 - -
16497 - Intake Air Temp. Sensor (G42): Signal too High
P0113 - 35-00 - -
17931 - Crash Signal from Airbag Controller: Implausible Signal
P1523 - 35-00 - -
18057 - Powertrain Data Bus: Missing Message from ABS Controller
P1649 - 35-10 - - - Intermittent

The first one I think is semi-permanent as I don't have the ECM power relay and all attempts to replicate it have resulted in failure. I think the last three are as a result of the occasional "stumble" on shutdown. I'll try rusky's idea and see if that stops these codes from popping up. With these codes present, will the ECU still do the tests necessary to set readiness?

[Mad Cow]

I get the last 2 codes too, nothing to worry about since they don't even throw the CEL. I ended up removing them from the DTC table so they never show up but that's not necessary. First one shouldn't cause any problems either, AFAIK it doesn't trip the CEL either. As for the IAT sensor code, have you tried replacing the sensor? It could just be bad. Check the readiness monitors with a generic OBD2 scan tool, vcds doesn't show the difference between passed and unsupported. I just did an emissions test recently too and it passed every single monitor after I coded out SAI and cat monitoring, you'll probably be fine too. Worst case, look up your state's emission test laws, I found out that since my car's a '99 I can have up to 3 monitors not passed, might be similar for you.

[bhusted]

That's good to know about VCDS not showing the difference between not supported and failed. I should do more reading for the test, but a CEL is an automatic fail. According to this it looks like I can have 2 "Not Ready".

I did some research tonight about the IAT and I think that it's integrated into the MAF on the V8 cars. The MAF is essentially new and I get the same code with my spare one, which makes me think it is false.

[Mad Cow]

If you pass the readiness portion but still have a CEL, maybe look into temporarily disabling the IAT code for the test. Probably best to ask the ever-helpful ddilenger about that.

[bhusted]

I may need to talk to him about that. I cleared the code again and made it through 2 long drives and a short trip before the IAT code came back. I still think it's the shutdown that's causing a false code to pop up. I'll work on the ecu power source that rusky mentioned and see if that clears it up. I'm getting tired of the cluster beeping at me every time I shut it down though.

[k0mpresd]

those missing message dtc's can be coded out very easily in a few different ways.
iat code can be removed as well without much of a fuss.

you can check the sensor in a measuring block just to confirm its working correctly.

[bhusted]

Thanks. I may be coming to you for some guidance on getting rid of some of those dtc's. I'm going to do log of the IAT just to make it's all good.

[bhusted]

Still working on this... It seems that the CEL will stay off for 3 cycles of the ignition switch and then it will come up with the IAT code. I worked for several hours last night and this morning trying to track down the stumble on shutdown, but I'm still coming up empty.

I think that this all stems from the lack of the infamous "ECM Power Relay". I've been experimenting with replicating the relay in many different ways and no matter what I do, I get a short stumble from the engine and beeping from the cluster when I turn off the key.

[mk1 rabbit gti]

Have you tried using an 01 harness and ecu?

[bhusted]

Have you tried using an 01 harness and ecu?

I am using an '01 ECU now that I've switched to the AWN ECU. I also re-pinned the ECU plugs in the engine harness to match the newer ECU. For all intents and purposes it is an AWN harness. The issue comes from running the ECU with older body harness and how the ECU receives power. Short of using a 2000+ dash/body harness on the car, I don't know what to do...

[Mad Cow]

There's got to be something about the DBC dash harness that causes this, maybe it could even be some sort of module or something that's different. I personally think it's something to do with the ECU power and immo circuits. I just find it odd how we both have the same problem but very different symptoms. You have the shutoff stumble and IAT code, while I get the ECU staying powered for half an hour after shutoff and the motor not shutting off as quickly as it does when compared to manually removing power from the ECU.

[mk1 rabbit gti]

I would have thought the 99.5 and 2000/01 dash harness would be the same. Have you tried messaging a4v8swap on motorgeek? He might be able to help you with the wiring issues.

[bhusted]

I would have thought the 99.5 and 2000/01 dash harness would be the same. Have you tried messaging a4v8swap on motorgeek? He might be able to help you with the wiring issues.

The difference in the dash harness is DBW vs DBC. Additionally, the ECU file I'm using is meant to utilize an immobilizer, which was not equipped on any B5 sold in North America. Fooling the ECU into thinking that the immobilizer is okay is a combination of hardware and software. I have spoken to him and he just ran with the automatic trans ECU, so he did not have this issue. I had none of these issues until swapping to the flashed AWN ECU. The issues it created are far less than the ones it solved, so at least it was progress.

There's got to be something about the DBC dash harness that causes this, maybe it could even be some sort of module or something that's different. I personally think it's something to do with the ECU power and immo circuits. I just find it odd how we both have the same problem but very different symptoms. You have the shutoff stumble and IAT code, while I get the ECU staying powered for half an hour after shutoff and the motor not shutting off as quickly as it does when compared to manually removing power from the ECU.

I have to agree with you about the ECU and immobilizer circuit as the cause. I've considered adding a separate toggle switch to cut power to pin 21 before turning off the key to get proper shutdown. I thought I'd be achieving this by adding a relay to the immobilizer power circuit.

[mk1 rabbit gti]

Who flashed your ecu? Sounds like your problems can be fixed by deleting and flashing an s6 manual tune.

[bhusted]

Who flashed your ecu? Sounds like your problems can be fixed by deleting and flashing an s6 manual tune.

I am running a manual S6 file, but as the S6 was only offered as a manual in Europe, I'm stuck with the immobilizer part as well.

[Mad Cow]

Who flashed your ecu? Sounds like your problems can be fixed by deleting and flashing an s6 manual tune.

It's nothing to do with the flash, it's definitely a hardware problem since I have a completely different ECU that has problems in the same circumstances. The J271 relay is a weird thing, I've spent hours reading up on it, I've even read the official Bosch documentation, but I still don't understand it. It's a part of the power circuit, but it acts differently when attached to an immo ECU, there's some weird electrical trickery going on. Usually the ECU grounds the coil, but there are also some circumstances where it'll feed 12v into the same pin that's usually grounded (pin 21), no idea why. Here's a wild guess: maybe the ECU doesn't go through the conditions needed to open the relay because of the loss of immo components/circuit (maybe it's waiting for a certain canbus message or voltage on a certain pin), so it keeps it powered until the main power capacitor inside the ECU drains enough that it can't keep the relay closed anymore. Or it could just be a side effect of the craziness used to make the relay work like I said earlier.

I've considered adding a toggle switch between the relay and pin 21 too, hacky as all hell but probably the best way to keep yourself from pulling all your hair out.

[bhusted]

I've considered adding a toggle switch between the relay and pin 21 too, hacky as all hell but probably the best way to keep yourself from pulling all your hair out.

I'm glad that I'm not the only one pulling my hair out over this. One of the things that baffles me is that adding a standard 5pin relay inline cannot sufficiently isolate that pin.

[mk1 rabbit gti]

If you didn't have any problems before switching to a 01+ ecu, then it's either the ecu, or the body harness not communicating with the ecu. I'd put the 2000 ecu back in until you can swap out to a newer dash harness. No sense pulling your hair out if you don't have to. Just my 2 cents.

[bhusted]

If you didn't have any problems before switching to a 01+ ecu, then it's either the ecu, or the body harness not communicating with the ecu. I'd put the 2000 ecu back in until you can swap out to a newer dash harness. No sense pulling your hair out if you don't have to. Just my 2 cents.

I'd rather go bald than swap the dash harness.