Symptoms:

This 2003 Silverado truck no start condition started last week after replacing the fuel pump. It ran good for a while but after a few days, the no start happened again but this time it is intermittent. It is also accompanied by fault code P0179 which refers to fuel composition sensor (FCS) located at the left rear of the engine compartment.

Diagnostics for 2003 Silverado no start:

As some automotive technicians have suggested, the aftermarket fuel pump we used was removed and replaced with an OEM fuel pump from the dealer. At the time of removal, we found out the fuel pump pressure was 45 lbs. Reset the fault code and road tested the vehicle but the engine quit after 45 minutes of driving.

Scanned the codes and code P0179 came out again. Took a small hammer and tap the sensor lightly and the engine re-started. Drove the truck to the shop and when testing with the scanner, the FCS gave an output frequency of 171 hertz signal.

Did voltage readings on FCS terminal plugin wires and we found the following readings at KOEO (key on engine off):

pink wire (power) reads 12 volts, OK
black wire (ground) reads below 0.250 volt, OK
white wire (frequency signal) reads 171 hertz (Note: a low reading of 50HZ indicates gasoline fuel and 170HZ as ethanol fuel and the tank has only gasoline fuel on it).

Sensing the tapping made the difference in operating the FCS, we replaced the sensor and also drained the fuel tank incase it was contaminated. We also replaced the fuel filter and reset the fault code. Took it for a road test and code never back.

Notes:

This fix is available if you read GM service bulletin about using and testing the FCS for this truck. ATS can give it to members upon request.

This 2003 Silverado no start fix should not be done by yourself unless assisted by a licensed mechanic or have the necessary automotive training to prevent damage to your engine.

Thanks,

Richard