ECM Code EO19 - Shorted Fuel Pump Circuit: Notes

TEST CONDITIONS:  Code EO18 clear. Engine RPM at zero. Crank input to ECM at zero volts (not cranking). Coolant light in bulb check (key on/engine off).

FAILURE CONDITIONS:  Fuel pump feedback voltage greater than or equal to 11 volts for 3 seconds (fuel pump powered with engine not running).

ACTION:  ECM turns on "ENGINE CONTROL SYSTEM" light. ECM commands BCM to display "SERVICE SOON" message on CCDIC panel.

The fuel pump receives power from circuit No. 120. Circuit No. 120 is fed by fuel pump relay and oil pressure switch. The fuel pump relay is controlled by the ECM. The relay is energized for 2 seconds with key on to provide fuel pressure for starting.

The oil pressure switch is provided as a backup. Normal operating engine oil pressure will close the normally open oil pressure switch contacts, providing a connection between circuit Nos. 239 and 120. If a relay fault occurs, the engine will continue to run as the oil pressure switch powers fuel pump.

The ECM monitors voltage on circuit No. 120 to detect fuel pump voltage faults. Code EO19 is set when fuel pump feedback circuit, ECM pin "D9", is at 11 volts or greater when the fuel pump feed voltage should be zero volts.

1. With key on/engine off, fuel pump should not be running and the fuel pump feedback (ECM parameter ED10) should be zero volts. The fuel pump is energized for 2 seconds with key on. After initial 2 second run, the fuel pump will not be powered until ECM sees distributor reference pulses from HEI.
2. This branch of diagnostic chart checks for shorted oil pressure switch contacts, powering fuel pump at all times.
3. Checks the ability of the fuel pump relay to provide power to fuel pump with a relay or relay drive circuit fault.
4. Checks for a short to the 12-volt power source in circuit No. 120.
5. Checks the ECM relay drive circuit for a fault that allows fuel pump relay coil to be energized continuously with key on.