Hello, I took my Avalanche to have ONLY the whole undercarriage washed/cleaned (high pressure hose) due to the fact that I had the transmission re-built and wanted to have it clean for if there was to be any leaks, etc... afterwards. After driving off from the shop that did this for me (about a 1 mile distance), the engine started to idle rough, no power, the check engine light came on, and it will not stay running unless I keep the gas pedal accelerated a bit.

I recently had the truck scanned, and it is giving me 6 fault codes:

P0120-THROTTLE POS SENSOR/SWITCH A CIRC ERROR
P0300-RANDOM/MULTIPLE CYLLINDER MISFIRE DETECTED
P1125-APP SYS
P1516-ELECTRONIC THROTTLE MOD THROTTLE POS
P2108-THROTTLE ACTUATOR CTRL MOD PERF-TAC
U0107-LOST COMM WITH THROTTLE ACTUATOR CTRL MOD

I am imagining that these faults are related one way or another from the fact that something got wet? The truck was running 110% PERFECT prior to this.

The only thing that I have done since then is changed the spark plug wires, and inspected all of the AC DELCO iridium plugs which they were fine....I cleaned them up with carb cleaner and a soft used toothbrush.

Can anyone think what might of gotten wet or what would bring up all of these fault codes? The truck only has around 25,000 miles (hardly used) and is currently unusable due to this. BTW, you can even eat your dinner off of the engine....that is how clean the motor is.

Thanks.

UPDATE, I have determined that the number 7 cylinder is not firing (piston on the driver side closest to the driver). I disconnected one by one the connectors to each coil with the engine running....and that is where I noticed no change on the engine idle with the connector to cylinder number 7 disconnected. A test was performed on that coil while turning the engine over, and spark was there. STRANGE. To eliminate doubts, I even replaced that spark plug, and switched coils to see if maybe a faulty one was in play, but the engine idles still the same.

The truck has been sitting for 3 months now with this problem.

Thanks.

 

Run it to dry it out, then clear the codes