Fuel Pump Signal: Description and Operation

PURPOSE
The fuel pump voltage signal is used by the control module as a reference to determine fuel system electrical loading and circuit integrity.

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

With PCM/VCM systems DTC 54 (VCM is DTC P1222) will set if the voltage at control module fuel pump signal terminal is less than 2 volts for 1.5 seconds since the last reference pulse was received. This DTC is designed to detect a faulty relay, causing extended crank time, and the DTC will help the diagnosis of an engine that "Cranks But Will Not Run".

With ECM systems DTC 54 will set if the voltage at control module fuel pump signal terminal is less than 2 volts for 5 seconds since the last reference pulse was received. This DTC is designed to detect a faulty relay, causing extended crank time, and the DTC will help the diagnosis of an engine that "Cranks But Will Not Run".