Open Fuel Pump Circuit

TEST CONDITIONS
RPM greater than or equal to 24.

FAILURE CONDITIONS
Fuel pump feedback voltage less than or equal to 2 volts for 1 second.

ACTION TAKEN
ECM commands BCM to display "Service Soon" message on Driver Information Center (DIC).

DESCRIPTION
The fuel pump receives power from CKT 120 through either the fuel pump relay or the oil pressure sensor. The ECM energizes the fuel pump relay for 2 seconds at key on to provide fuel pressure for starting. After the 2 second fuel pump prime, the ECM will not power the fuel pump relay until distributor reference pulses are received indicating that the engine is turning (crank or run). The oil pressure sensor is provided as a "backup" to the fuel pump relay. Normal operating engine oil pressure will close the normally open switch contacts in the oil pressure sensor, providing a connection between CKT 239 and 120. If a relay fault occurs, the engine will continue to run as the oil pressure sensor powers the fuel pump. A vehicle with the relay inoperative will crank until oil pressure builds (oil telltale off) then start and run as the switch provides power to the fuel pump. The ECM monitors voltage on the fuel pump power CKT 120 to detect fuel pump voltage supply faults. Code E020 is set when the ECM sees the fuel pump not energized (0 volts on the feedback) with the engine cranking or running. The code is designed to detect a fuel pump relay fault; relay not powering the fuel pump.

NOTES ON FAULT TREE
1. Checking for engine to start with fuel pump powered through fuel pump relay. If car does not start, go to diagnosis on the next chart.
2. 0 volts with engine running indicates an open from fuel pump power circuit to ECM - fuel pump relay is not at fault.
3. Checking for proper control of the fuel pump relay by the ECM.
4. Checking for open from fuel pump fuse to relay pin "4."
5. Checking for open from relay pin "5" to ground.
6. If light turns on, then all relay circuitry is OK. Fault is the relay.
7. If the relay or relay drive circuits are grounded, the ECM may be damaged by excessive current draw. Repair the fault and check for proper operation.
8. Fault is most likely at ECM connector or ECM. Before ECM is replaced, perform "ECM Replacement Check". Chart C-1. Testing and Inspection

NOTES OF INTERMITTENTS
If Code E020 is stored as history, unplug the oil pressure sensor, start the engine, and allow to idle. Manipulate affected wiring, check the relay for proper installation into socket. If the fault is induced, the engine will stall, Code E020 will set. If Code E020 sets without an engine stall, the cause is a intermittent open CKT 120 between ECM pin E13 and splice to fuel pump relay.