ECM Code EO19: Shorted Fuel Pump Circuit: Action:

ECM commands BCM to display SERVICE VEHICLE 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 back-up. Normal operating engine oil pressure will close the normally open oil pressure switch contacts, providing a connection between circuits No. 239 and No. 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 terminal E13, is at 7 volts or greater when the fuel pump feed voltage should be zero volts.

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

Test Number 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.

Test Number 2) This diagnostic chart branch checks for shorted oil pressure switch contacts, powering fuel pump at all times.

Test Number 3) This checks for fuel pump relay drive circuit fault.

Test Number 4) This checks for a short to 12-volt power source in circuit No. 120.

Test Number 5) This checks the ECM relay drive circuit for a fault allowing fuel pump relay coil to be energized continuously with key on.