I've got a track car, 2011 Grand Sport A6. We stripped a lot of modules and wires out of the car recently. It would be easier to say what is left in the car instead of what was removed. It still has the ECM, BCM, EBCM, IPC, HUD and RCDLR. It also has the 2nd gen LG Track Box. The car ran this past weekend great for 2 days, then on the 3rd day, all sorts of error messages popped up on the dash, and the ABS locked the front wheels up. After cycling the power, it was able to move and brake.

I have been pulling codes with a Tech 2 and keep getting different codes each time. The latest codes I pulled are shown below:

Connected Tech2 and scanned these codes:
EBCM No Communication
U1000 RCDLR Class 2 Data <-----showing as passed
U1000 IPC Class 2 Data
U1000 BCM Class 2
U2108 Lost Comm with ABS
U2106 Lost Comm with TCM

I cleared the DTCs and ran it again, this time I only showed these:
EBCM now communicating, no codes
U1000 RCDLR Class 2 Data <-----showing as passed
U1000 IPC Class 2 Data

The Instrument Panel is working fine. I think the RCDLR is working, not really sure as we put the Key FOB right on the Aux RF receiver. I should mention that the Theft Lock light has been illuminated solid since we removed all the door modules. I've checked continuity on all the Class 2 wires. They are all good.

Could the GMLAN wires spliced to the LG Trackbox cause the Class 2 wiring circuit to do this?
Also, what are the "Symptom Codes" are on the Tech 2 DTC screen?

 

Check your grounds. Things moving around like that usually means a loose connection...

Nick

 

I've checked all the grounds at the A-pillar and B-pillar, both sides. I removed the LG Track Box. That didn't change anything. I still keep getting these codes:

ECM - P0532 AC Pressure Sensor Circuit Low Voltage - Symptom 00 - Last Test: Failed/Current
RCDLR - U1000 Class 2 Data Link - No symptom reported - Last Test: Failed/Current
IPC - U1000 Class 2 Data Link - No symptom reported - No test reported
BCM - U1000 Class 2 Data Link - Symptom 00 - Last Test: Failed/Current
BCM - B3715 Front Wiper Relay Drive Circuit Short to Battery or Open - Symptom 05 - Last Test: Failed/Current
BCM - B2580 Headlamp High Beam Control Circuit Short to Ground or Open - Symptom 06 - Last Test: Failed/Current

Car communicates with ECBM, no codes reported. All gages are working. Car still starts.

 

Update.....

We have triple checked all grounds and all 12V supplies to each module. They are all good.
We built a new Serial 2 data line. Recall only the the BCM, IPC, RCDLR and HUD are still in the bus. All other modules and wires have been removed from the car.
We still keep getting these errors:
- IPC - U1000 Class 2 Data Link
- HUD - U1000 Class 2 Data Link
- BCM - U1000 Class 2 Data Link
Car still starts. All gages work. HUD works.
Only dash light is the anti theft car lock.

We measured each serial data line individually with a oscilloscope and the only module that is providing power/data is the BCM (0-7.8V).

We pulled each module from the car and bench tested them individually.
-HUD provides no voltage on the serial line.
-IPC and RCDLR both provided good pulse voltage/data (0-7.8V), but only for 5 seconds then nothing. This is repeatable.

We are getting a new RCDLR and hoping to find an IPC tomorrow to swap out see.

Any software/serial 2 data gurus out there have any other ideas what is going on?

 

Any updates?