Circuit Description
The engine control module (ECM) provides a ground to the coil side of the fuel pump relay. When the ignition switch is first turned On, the ECM energizes the fuel pump relay, which applies power to the fuel pump. The ECM enables the fuel pump relay as long as the engine is cranking or running, and crankshaft reference pulses are received. If no crankshaft reference pulses are received, the ECM de-energizes the fuel pump relay after 3 seconds. If the ECM detects high voltage on the fuel pump relay control circuit, this DTC sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1231 Fuel Pump Relay Control Circuit High Voltage
Conditions for Running the DTC
| • | The ignition is ON or the engine is running. |
| • | The ignition voltage is more than 10 volts. |
| • | DTC P1231 runs continuously once the above conditions are met. |
Conditions for Setting the DTC
| • | The ECM detects that the commanded state of the driver and the actual state of the driver do not match. |
| • | The above conditions are present for more than 5 seconds. |
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
Listen for a click when the fuel pump relay operates. When the fuel pump relay is commanded On with the scan tool, the ECM pulses the fuel pump relay ON and OFF several times.
For an intermittent condition, refer to Intermittent Conditions .
Fuel Pump Relay Terminal Identification | |
|---|---|
FP Motor | FP Control |
Ignition 1 Voltage | B+ |
Front of Vehicle | |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Engine Controls? | Go to Step 2 | |
Does the fuel pump relay turn ON and OFF? | Go to Step 3 | Go to Step 4 | |
3 |
Did the DTC fail this ignition? | Go to Step 4 | Go to Diagnostic Aids |
Does the test lamp pulse ON and OFF? | Go to Step 6 | Go to Step 5 | |
5 | Test the control circuit of the fuel pump relay for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 7 |
6 | Test for shorted terminals and poor connections at the fuel pump relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 8 |
7 | Test for shorted terminals and poor connections at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 10 | Go to Step 9 |
8 | Replace the fuel pump relay. Did you complete the replacement? | Go to Step 10 | -- |
9 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | Go to Step 10 | -- |
10 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 11 |
11 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | System OK | |
