2002 LS1 Fuel-Pump Electrical Diagnosis
2002 LS1 fuel-pump diagnosis that separates PCM command, relay/feed/ground faults and circuit problems from an actually failed pump.
Prime is brief without reference pulses.
With ignition ON the PCM runs the in-tank pump briefly. It keeps the pump on while cranking/running when ignition reference pulses are present; without those pulses the PCM turns the pump back off after roughly two seconds.
Low or zero fuel pressure does not prove the pump. Prove pump command and the loaded electrical path before condemning the in-tank assembly.
- Confirm whether the pump receives the expected prime/command.
- Separate relay control from relay switched-power operation.
- Check feed and ground under the failed condition, not only unloaded continuity.
- If pressure is low but the circuit is correct, continue the fuel-system diagnosis to separate pump capability, regulator and internal pressure loss.
- If the circuit fails, repair the command/feed/ground/connector fault and retest pressure.
A hotwire harness can make the factory circuit a relay trigger while a separate high-current path powers the pump. Identify whether the car is factory-wired, hotwired or unknown before following a stock current path.
AFTER THE FAILURE IS PROVEN
Use the proven failed branch—not the original symptom—to choose the replacement. Go from diagnosis to the Parts Verdict →