Fuel Pump Relay: Description and Operation

Fuel Pump Relay Circuit Wiring Diagram:

NOTE: Because different models and engine applications vary in wire colors, circuit numbers, and pin numbers, the above image is a typical example. Refer to COMPUTERS AND CONTROL SYSTEMS/SCHEMATIC AND ROUTING DIAGRAMS for specific schematic applications.

OPERATION:
The status of the fuel pump CKT 120 is monitored by the PCM at terminal "B12" and is used to compensate fuel delivery based on system voltage. This signal is also used to store a Diagnostic Trouble Code (DTC) if the fuel relay is defective or fuel pump voltage is lost while the engine is running. There should be at least 12 volts on CKT 120 for at least 2 seconds after the ignition is turned "ON", or any time the reference pulses are being received by the PCM.