ECM Code EO20 - Open Fuel Pump Circuit (Fuse Not Blown): Notes

TEST CONDITIONS:  Engine RPM greater than or equal to 24.

FAILURE CONDITIONS:  Fuel pump feedback voltage less than or equal to 2 volts for 3 seconds or more.

ACTION:  ECM stores code as current until engine is turned off. ECM turns on "ENGINE CONTROL SYSTEM" light. ECM commands BCM to display "SERVICE NOW" message on CCDIC panel.

The ECM monitors voltage on circuit No. 120 to detect fuel pump voltage faults. Code EO20 is set when ECM sees that 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).

1. If engine starts with a current EO20 code, this indicates that engine started with fuel pump powered through the oil pressure switch. Fuel pump relay circuit may be at fault.
2. Zero volts with engine running indicates an open from fuel pump power circuit to ECM. Fuel pump relay is not at fault.
3. This step checks ECM's ability to energize relay coil.
4. This step checks for an open circuit from fuel pump 10-amp fuse to relay pin No. 1.
5. This step checks for an open circuit from relay pin No. 2 to ground.
6. If light turns on, then all circuitry is okay. Code may be caused by fuel pump relay.
7. Fault is most likely at ECM connector or ECM. See CHART C1 - ECM REPLACEMENT CHECK before replacing ECM.