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geoffsta99
02-28-2013, 08:59 AM
I keep getting this code:

17925 - Power Supply Relay for ECU (J271 or J363)
P1517 - 35-00 - Electrical Malfunction

This is because i'm swapping the 1.8T into another car, and i'm currently tapping into the injector circuit for ECU power.

So, I saw this on 034's website...
http://www.034motorsport.com/wiring-solutions-relays-fuses-breakers-fuse-block-panel-pre-wired-wrelay-p-496.html

Will this allow me to safely, and correctly run power to the ECU, and clear the code?

Thanks for the help.

geoffsta99
02-28-2013, 02:03 PM
Well it looked right, so I ordered it... We'll see.

ddillenger
02-28-2013, 02:13 PM
http://wiki.obdtuning.com/images/a/ac/VAG_ME7.x.jpg

Power to red, ground to blue. Obviously using the proper fuses and relays. That is all the ecu needs (powerwise). If your car isn't using factory gauges/etc, just run the green wire to the K-line in the OBD plug, and you'll even have communications with a scanner.

walky_talky20
02-28-2013, 02:27 PM
Well it looked right, so I ordered it... We'll see.

Wow. Not sure if I could have come up with a more expensive solution than that! You just needed a $5 relay.

J271 is the "ECM Power Supply Relay". Interestingly, that relay is controlled by the ECU itself.

ECU Pin 21 is the ground trigger for the relay.
The Relay's 12V+ output drives 2 fuses: 1 for the VVT (if equipped), and 1 for the ignition coil packs (fuse #29).
The power line to the coil packs is also connected to ECU pin 121 << This is how it monitors the operation of that relay, and thus throws that code for it.

I'm pretty certain the above diagram is incorrect with regards to pin 21 (should be pin 121, methinks).

k0mpresd
02-28-2013, 02:54 PM
I'm pretty certain the above diagram is incorrect with regards to pin 21 (should be pin 121, methinks).

i would have to politely say that the diagram is correct in regards to powering the ecu to establish communication. [:)]

though, there are obviously other power lines involved as well. which is probably where your pin 121 comes in to play.

Mad Cow
02-28-2013, 04:31 PM
i would have to politely say that the diagram is correct in regards to powering the ecu to establish communication. [:)]

though, there are obviously other power lines involved as well. which is probably where your pin 121 comes in to play.

I would guess that pin 121 isn't needed for operation but is only used to monitor the relay. OP, you really don't need that fuse panel thing. I don't know what car you're swapping it into but I was able to get everything powered up fine with no relay code on my previously DBC 30v, though I did have to get a bit creative.

geoffsta99
02-28-2013, 08:12 PM
I would guess that pin 121 isn't needed for operation but is only used to monitor the relay. OP, you really don't need that fuse panel thing. I don't know what car you're swapping it into but I was able to get everything powered up fine with no relay code on my previously DBC 30v, though I did have to get a bit creative.

It's going into a B5 S4 chassis. I've been able to keep most of the electrical connections OEM, but A4 and S4 ECU's receive power on different pins on the orange chassis connector in the ECU box. So, I snipped the blue/black power wire about 10"off the ECU, and crimped it onto the gang connection for the fuel injectors. (thats how it works on the s4, but not for the a4 apparently.) I'm looking to run power the right way to get rid of the code.

I don't mind running that harness, if it will accomplish the same relayed circuit for the ECU. Chances are i'll be running other components in the duture, and having that separate circuit might be nice.

ddillenger
02-28-2013, 08:51 PM
I am 100 percent certain pin 21 gets power, and is not a switched ground. I've personally powered up about 100 ecu's this way without incident. I'm sure k0mpresd has done quite a few more. What happens on the me7.5 when that pin isn't powered? No communication with my flashing software.

Something worth noting: The b5s4 doesn't need this wire powered, nor does the 2.7t a6 that came equipped with me7.1. Me7.1.1 and later require it. IIRC, it gets powered via relay 429 (when installed in the car).

geoffsta99
03-01-2013, 05:23 AM
I am 100 percent certain pin 21 gets power, and is not a switched ground. I've personally powered up about 100 ecu's this way without incident. I'm sure k0mpresd has done quite a few more. What happens on the me7.5 when that pin isn't powered? No communication with my flashing software.

Something worth noting: The b5s4 doesn't need this wire powered, nor does the 2.7t a6 that came equipped with me7.1. Me7.1.1 and later require it. IIRC, it gets powered via relay 429 (when installed in the car).

So I may already be getting power there... The car fires right up and runs, and I can communicate with all modules.

The Blue/Black wire I snipped was off Pin #3, and I currently have it crimped to the gang connection for the fuel injectors... I have not touched the wire from #21. Do I need to supply power to pin #3, or pin #21? And if so, will that relay work?

walky_talky20
03-01-2013, 07:54 AM
I am 100 percent certain pin 21 gets power, and is not a switched ground.

Hmm. That's not what I'm seeing in the Bentley, though. I'm going to respectfully post the 2001 1.8T AWM wiring diagram page showing the J271 ECM Power supply relay:
<Respectfully posted image>
http://i1053.photobucket.com/albums/s469/travrach1/B5ECMrelay.jpg
</Respectfully posted image>

As you can see, pin #21 is definitely a ground trigger output from the ECU. It certainly *will* see 12V+ (backfeed through the relay coil) during times it is not actively triggering the relay. But the purpose of the pin is to be a ground trigger output as far as I can see from the diagram.

I've not done any bench testing of ECU's or any of that. So I'm just going on the factory diagram here. I have no trouble believing that it's more complex than that: like refusing to boot until it saw 12V+ backfeed onto pin 21. From what you are telling me from your experience with bench powering these things, I think we are both correct. It is a ground trigger, AND it needs to see 12V.

Respectfully Submitted,
Walky

un1ko
07-19-2013, 07:10 AM
Subscribed.

I'm running into similar issues.

ddillenger
07-19-2013, 07:18 AM
FYI, this relay (J271) is integrated. It can, however, be removed from diagnosis within the flash as though it were never installed. This removes the code, and prevents any issues that may arise from it's absence.

Mad Cow
07-20-2013, 08:35 AM
FYI, this relay (J271) is integrated. It can, however, be removed from diagnosis within the flash as though it were never installed. This removes the code, and prevents any issues that may arise from it's absence.

Interesting, are there any side effects? What is the point of the relay anyway?

geoffsta99
07-23-2013, 01:49 PM
Interesting, are there any side effects? What is the point of the relay anyway?

The point of the relay is to power the cam adjustment valve (VVT) and the (4) ignition coils when the ignition is switched on.

un1ko
08-05-2013, 08:52 AM
Sorry to thread jack. Hope I can get some help. Here my build asking about it S4 with A4 Heart (http://www.audizine.com/forum/showthread.php/532329-Audi-S4-with-a-2-0T-heart-Build/page3) if you want to reply here so I don't intrude geoffsta99 thread


I'm reading this post and it's going way over my head. I wish there was a book "wiring for dummies" [headbang]

I feel like I'm inactivating a bomb, don't know what wire to cut and if I cut the wrong one it'll explode. Lol!

Right now based on the information I got is to cut pin 4 from the Orange connection, so I need to run a wire from J271 is the "ECM Power Supply Relay" which I can't find. This weekend I went though the each wiring harness connection for an 1.8T AWM and a 2001 S4. I'm somewhat color blind, so I may of mixed the colors a little bit. Purple, Blue are my weak spot. Lol!


I do have a Bentley for the A4 AWM, but don't know how to read the wiring diagram.

http://i94.photobucket.com/albums/l109/un1ko/A4S4WiringHarnessConnectors_zpsc2c84000.jpg

un1ko
07-17-2014, 08:02 AM
Hey geoffsta99 - Did you get this resolved?


ddillenger - After reading what you said I discovered that is my issue. When flashing my ECU with the Maestro, it times out. . I drove Eurodyne crazy. Lol!


I guess my question is... Can bypass this relay or do I need to resolve this? I do need to continue flashing my ECU.

I'm thinking out loud.

With the N205 - I Connect it to T6at/3 - because the APB the N205 goes on goes to the G108 Heated o2 sensor. AWM does not have it. Both have G39 which is the heated o2 sensor for AWM and APB has it too. Also since the APB does not have S204 fuse.

For pin 121 - I should be ok - both connect to T10ar/1

For pin 21 - Will this work if I also connect this wire to T6at/3? Maybe add a fuse in between?


I also just found this. Audi_ECU_J271 (http://www.audicrazy.com/repair/Audi_ECU_J271.pdf)

Any help would be great. I feel like I'm getting so close. Thanks in advance for any help!!