DBW problems, G4+ Fury

[Pete_89t2]

Today after driving the car & shutting it down normally, I encountered to following errors upon keying it back on with the laptop connected: ECU Fault Code 73, Aux 9/10 supply error and ECU fault code 76, TP(main)/TP(sub) tracking error. Obviously this error puts the engine in the limp home/crippled mode.

I didn't attempt to start the car, but went straight into electrical troubleshooting. Checked out the relays (ECU main relay, DBW relay, fuel pump relay) and all checked out on the bench as good and I was unable to find any issues with the any of the loom wiring. The DBW relay coil gets +12V to its coil as it should when the ECU Main relay is energized on key on. The other coil terminal of the DBW relay coil should be pulled to ground when the G4+ powers up, through the INJ7 output, but it appears that isn't happening.

Any ideas on what to tackle next?

Thanks in advance!

[Adamw]

73 is likely just a symptom of the 76.  Code 76 means the TP main and TP sub signals dont match, the ecu doesnt know which one is correct so it disables the throttle by switching off the e-throttle relay - this will cause the code 73.  

[Pete_89t2]

You nailed it Adam. Turns out I had a slightly loose/intermittent connection at the GM throttle body connector which apparently caused the TP tracking error, which disabled the DBW relay (code 73). Found it by jiggling the connector shell, and then subsequently re-pinning the connector. After doing that, and running the APS & TPS calibration all is good to go.