2007 Audi S6 Engine Component Power Supply Relay

Alex Technician Colorado Posted   Latest   Edited  
Resolved
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2007 Audi S6 5.2L (BXA) 6-spd (09E) — WAUGN74F37N037044
P1576
P0102 — Mass or Volume Air Flow Sensor "A" Circuit Low
P1573
P010C — Mass or Volume Air Flow Sensor "B" Circuit Low
Engine Runs Poorly

Hey everyone. The customer states that they hit a parking curb with the front bumper and damaged some wiring running underneath the harmonic balancer/radiator area. They said that since they did that the engine barely runs. I repaired the wiring damage that I could see and replaced fuse SA5 that was blown. Started the engine and still runs very poorly and set DTCs for components on fuse SA5 circuit. The problem is that I now have 3 volts on fuses SA5, SA6, and SA7. I have 3 volts at both MAF sensors, both engine mounts, and all other components that fuse SA5 supplies power to on the Red/Blue wire, which was severed when the vehicle arrived.

I found that the master ECM is not grounding the Engine Component Power Supply relay with the key-on. The 3 volts I'm seeing on this circuit is coming from the ECM on the ground side of the components. I can back probe pin 32 green/gray wire at the ECM and apply ground. When I do this, the relay energizes and all components receive 12 volts. 

I load tested the 3 large brown ground wires at the master ECM connector, and have 12 volts at the 3 violet power supply wires as well, back-probed. Do I have a faulty ECM? I can't wrap my mind around how this wiring damage could result in a faulty ground driver in the master ECM. Is there some other input that the ECM needs to see to ground this relay?

Another discrepancy in the service info I have is it says J757 (Engine Component Power Suppy Relay) is for a 3.2 liter engine. This vehicle has the 5.2 V10.

Any help or insight is greatly appreciated. 

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Charles Technician
California
Charles
 

J757 is a production break, not engine specific. It is only found in production cars made after June of 2007. To me it sounds like you are getting feedback between through a couple wires touching. I would recommend opening up the harness, going about a foot on both sides of where is was damaged and repaired. Really eyeball all the wires in that area for any kinks, twists or frays. Maybe have…

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Alex Technician
Colorado
Alex
 

I have tried that, moved the front end into service position and inspected all the wiring very closely. There is not wire chaffing or kinking that I can see. I've tried monitoring fuse 5 voltage while wiggling the wires with no change found.

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Charles Technician
California
Charles
 

Can you post some pictures of the wires you repaired and shot of the area that it was damaged at?

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Charles Technician
California
Charles
 

I had some time this morning and went through some old help line posts. Saw a similar one to yours on an A7, the J271 relay would not power up and energize the J757 relay unless he manually grounded it. Ended up having an open power wire between that SA fuse panel in the left side under cowl electronics box and the ECM. There are more power wires to the ECM from than panel than just those 3…

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Michael Owner/Technician
Florida
Michael
   

I’m not an Audi ace but have been seeing many more of them lately so I’m here to learn. You didn’t definite all the codes, are you using a generic obd2 scanner? You might need to clear codes in all modules maybe the Engine module has some communication codes not in generic. What happens to the relay if those three fuses are pulled?

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Alex Technician
Colorado
Alex
 

There are tons of codes in multiple modules, and most of the codes will not clear. I'm trying to figure out how to upload my autologic pre-scan. The relay still does not energize with the fuses out, and I have 3 volts on the component side of all the fuses with all the fuses out. If I remove the relay and check for ground at relay pin 86, the ECM does not apply ground. However, I don't know if…

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Mike Diagnostician
Ontario
Mike
 

Hi Alex, Access to a scanner that will give you manufacturer specific fault codes might give you some more faults you won't see with generic OBD. The relay control circuit is monitored by the ECM and if you remove the relay it should flag a DTC for it. Have you tried monitoring the ground control side of the relay with a scope to see if there is even brief activation at key on and cranking?…

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Alex Technician
Colorado
Alex
 

I'm not sure if the ECM will attempt to energize the relay without seeing 12 volts from the relay coil. I do have tons of codes in multiple modules, most of which will not clear. I have checked to see if the ECM will ground the relay coil on pin 86 with the relay removed and it will not. I think my main concern is the 3 volts I'm seeing on the component side of fuses 5, 6, and 7 with the fuses…

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Zachary Mobile Technician
Texas
Zachary
 

Hello Alex, According to the research I've done, The power side of the engine component relay coil is supplied by the ECM power supply or Motoronic relay. It serves to reason that relay is functioning to some degree because the car runs (albeit poorly) and that relay supplies power to the ignition coils too (among other things.) You've also stated that grounding the control wire at the ECM…

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Alex Technician
Colorado
Alex Update
 

Thanks to everyone who responded. I will recheck this on monday and look into some of the things you guys suggested. I'll let you know what I find.

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Alex Technician
Colorado
Alex Resolution
   

Thanks again everyone for the suggestions. All I did was reconnect all of the sensors, cleared DTCs from all modules, and did a hard reset as Michael and Zachary suggested. After doing that the ECM started grounding the relay. Not sure what happened, but apparently there is a technical reason to clear codes on VAG cars. I got another Audi in today, an 07 A6 3.2. This car would not crank and no…

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