Circuit Description
The fuel pump relay is located in the underhood fuse block (UBFB). The engine control module (ECM) provides 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 feed back 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 the fuel pump relay is commanded OFF with the engine cranking.
DTC Descriptor
This diagnostic procedure supports the following DTC:
P0627 Fuel Pump Relay Control Circuit Open
Conditions for Running the DTC
| • | The engine speed is more than 40 RPM. |
| • | The engine controls ignition relay voltage is between 7.5-15 volts. |
| • | The ECM has commanded the fuel pump relay ON and OFF at least once during the ignition cycle. |
| • | DTC P0627 runs continuously once the above conditions have been met. |
Conditions for Setting the DTC
| • | The control module detects an incorrect voltage on the control circuit of the fuel pump relay. |
| • | The condition exists for less than 1 second. |
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
| • | For an intermittent condition, refer to Intermittent Conditions . |
| • | Fuel pump relay coil resistance is 70-115 ohms. |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Component Views or Engine Control Module Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 |
Does the fuel pump turn ON and OFF with each command? | Go to Step 3 | Go to Step 4 |
3 |
Did the DTC fail this ignition? | Go to Step 4 | Go to Intermittent Conditions |
Does the test lamp turn ON and OFF? | Go to Step 6 | Go to Step 5 | |
5 | Test the control circuit of the fuel pump relay for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 8 | Go to Step 7 |
6 | Replace the fuel pump relay. Did you complete the replacement? | Go to Step 8 | -- |
7 | Replace the engine control module (ECM). Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | Go to Step 8 | -- |
8 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 9 |
9 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK |
