ECM Code EO20: Open Fuel Pump Circuit: Action:

ECM commands BCM to display SERVICE VEHICLE NOW message on CCDIC panel. ECM monitors voltage on circuit No. 120 to detect fuel pump voltage faults. Code EO20 is set when ECM sees fuel pump is not energized (zero volts on feedback circuit) with the engine cranking or running. Code is designed to detect a fuel pump relay fault (relay not powering fuel pump).

NOTE: Test numbers refer to test numbers on diagnostic chart.

Test Number 1) If engine starts with a current Code EO20, this indicates engine started with fuel pump powered through the oil pressure switch. Fuel pump relay circuit may be at fault.

Test Number 2) Zero volts with engine running indicates an open from fuel pump power circuit to ECM. Fuel pump relay is not at fault.

Test Number 3) This checks ECM's ability to energize relay coil.

Test Number 4) This checks for an open circuit from fuel pump fuse to relay terminal No. 4.

Test Number 5) This checks for an open circuit from relay terminal No. 5 to ground.

Test Number 6) If light turns on, circuitry is okay. Code may be caused by fuel pump relay.

Test Number 7) If relay or relay drive circuits are grounded, ECM may be damaged by excessive current draw. Repair fault and check for proper operation.

Test Number 8) Fault is most likely at ECM connector or ECM. See CHART C1, ECM REPLACEMENT CHECK before replacing ECM.