Circuit Description
The fuel lift pump relay is controlled by the ECM, and provides power to the fuel lift pump.
Component Location
The fuel lift pump relay is installed in the engine wiring harness near the ECM. The fuel lift pump is mounted on the intake side of the engine.
Conditions for Running the Diagnostics
This diagnostic runs when the keyswitch is in the ON position and the lift pump timer has expired 1 minute after initial key ON.
Conditions for Setting the Fault Codes
The engine fuel lift pump signal circuit is detected to be greater than 0-VDC when the signal is turned off by the ECM.
Action Taken When the Fault Code is Active
The ECM illuminates the amber CHECK ENGINE lamp immediately when the diagnostic runs and fails.
The engine fuel lift pump will be disabled.
Conditions for Clearing the Fault Code
Perform a key cycle, and leave the key switch in the ON position for at least 2 minutes.
The fault code status displayed by INSITE? electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.
The ECM will turn off the amber CHECK ENGINE lamp after the diagnostic runs and passes.
The Reset All Faults command in INSITE? electronic service tool can be used to clear active and inactive faults.
Shop Talk
This fault becomes active if the ECM detects an open circuit at key ON, after the lift pump has cycled for 1 minute. Causes of this fault code include an open circuit in the electric fuel lift pump circuit.
If the fault code is intermittent, look for causes of an intermittent open circuit, such as loose pins and bad connections. This fault code can detect open circuit conditions only at key ON. The lift pump only runs at key ON and during cranking to aid in priming of the fuel pump gear pump.
The lift pump will run continuously if shorted to battery power. If the lift pump runs continuously, check for aftermarket modifications and wiring to the lift pump.
Possible Cause:
1) Fuel Lift Pump Relay failure
2) Engine Harness
3) ECM calibration
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