P0627

Wiring Diagram:

Fuel Pump Relay Control Circuit:

P0627- FUEL PUMP RELAY CONTROL CIRCUIT
The fuel pump relay is located in the underhood fuse block (UHFB). The ECM controls the fuel pump motor by supplying a ground to the fuel pump relay coil whenever the engine is cranking or running. When the fuel pump relay is commanded Off (circuit not grounded), the voltage level at the ECM should be high (ignition voltage). When the fuel pump relay is commanded On (circuit grounded), the voltage level at the ECM should be low. The ECM fuel pump relay feedback circuit uses a pull-up voltage (2.6-4.6 volts), which allows the ECM to individually differentiate between an open, short to ground or short to voltage. During engine crank, the ECM will command the fuel pump relay Off for a very short amount of time during which it will test for an open/low voltage condition. This test is only performed once during engine crank. DTC P0627 will set if the ECM detects an open fuel pump relay control circuit when fuel pump relay is commanded Off with engine cranking.

DTC PARAMETERS
DTC P0627 will set if fuel pump relay feedback voltage is between 2.6 - 4.6 volts (ECM pull-up voltage) indicating an open circuit during the 250 microsecond test phase when fuel pump relay is commanded Off when:
^ Condition exists for longer than 250 microseconds (0.00025 seconds)
^ Engine is cranking
^ Battery voltage is between 7.5 and 15.0 volts

DTC P0627 diagnostic runs only once during engine crank when the above conditions have been met.

P0627 is a type D DTC

DIAGNOSTIC AIDS

IMPORTANT: The ECM will only energize the fuel pump relay when the engine is cranking or running. If the ignition is turned On and the engine is not cranking, the fuel pump will NOT run.

To locate an intermittent problem, use Scan tool to command the FUEL PUMP RELAY On and Off while wiggling circuit 497.

Fuel pump relay coil resistance: 70-115 ohms.