Guys,
I pressured washed my vette only exterior, wheels, under body on the outer bottoms not the engine. I was driving home probably 3-4 miles from 25 miles destination Reduced engine power, service traction sys came on the dash along with check engine light and traction cotrol light and the car was running some what rough and loss of majority of power. I was able to make it home 25 miles in reduced engine power mode. i thought it was odd that this occurred after pressure washing my car so i thought possibly was related from that. I pulled the DTC codes from the dash following codes came up: 28-tcs c1278C, 10-pcm P1221 H C, 10-pcm P1120 H C. When my friend came over hooked up the scanner following codes came up: P1221 TPS performance/fuel pump circuit, P1571 TCS PWM circuit no frequency/signal, P1120 throttle position sensor circuit 1. I cleared the codes and the check engine light and traction control light on dash cleared. I took it for spin is driving fine but soon as i drove like a block Reduced engine power/service traction control message along with check engine light and traction comtrol light came back on dash.I researched on this forum and foud other people had similiar issues but with different dtc codes but the common codes we all had was 28-tcs c1278c. I let the car sit in my garage from saturday to saturday I drove to my bank which is about 1/4 miles all the dtc and messages didn't come back on been driving fine. so far i drove roughly 20 miles over this weekend and today i drove to work 25 miles the car is running fine.

everytime I was the car the water accumlates on both sides on the top of the frame rails where there is a ground & few connectors. each time i use paper towel to soak up the water. SOOOOOOO was all this just from a ground or connector moisture got into from washing the car????

 

My best guess is wheel speed sensor connections.

 

Only 1 comment????

People who had same or similar problems in the past, chime in. I'm very perplexed. Would like answers to this problem.

 

Depending how crazy you went with the power washer on the passenger side front wheel well and around the fender vent in front of the passenger door, you may have gotten your PCM and other modules wet. They all reside just behind the fender and there is an access panel in the wheel well. The connections to the PCM have gaskets so it's doubtful water was that intrusive, but it is plausible. Your udders on each side of the cowl could also be clogged. That can lead to water pooling up in the cowl and leaking in behind the dash and getting on the BCM in the passenger foot well. In either case, wet modules and electrical equipment is no good. Other then those ideas, a bad ground connection further disrupted by standing water somewhere could potentially cause problems. The list of possibilities is pretty extensive when you start blasting the car with high pressure water. Even if it is only on the exterior. I recommend washing the old fashion way with a standard hose/less pressure.

 

The Reduced Engine Power (REP) most likely is associated with the P1120. Any error in the throttle position circuit, will IMMEDIATELY throw you in to REP.

Make sure that sensor is clean and dry. Clear ALL the DTCs and see what comes back.

Bill