Circuit Description
The fuel pump receives power from CKT 120 through the fuel pump relay. The PCM energizes the fuel pump relay for 2 seconds at key ON to provide fuel pressure for starting. After the 2 second fuel pump prime, the PCM will not power the fuel pump relay until 4X reference pulses are received indicating that the engine is turning (crank or run). The PCM monitors voltage on the fuel pump power CKT 120 to detect fuel pump voltage supply faults. DTC P0231 is set when the PCM sees the fuel pump not energized (2 volts or less on the feedback circuit) with the engine cranking or running.
Conditions for Running the DTC
Engine speed 24 RPM or greater.
Conditions for Setting the DTC
Fuel pump feedback 2 volts or less for 1.3 seconds.
Action Taken When the DTC Sets
| • | The Malfunction Indicator Lamp (MIL) will not illuminate. |
| • | The PCM will command a message to be displayed. |
| • | The PCM may record operating conditions at the time the diagnostic fails. This information will be stored in the Failure Records. |
Conditions for Clearing the Message/DTC
| • | The PCM will turn the message OFF after one run and pass of the diagnostic test. |
| • | A History DTC will clear after forty consecutive warm-up cycles with no failures of any non-emission related diagnostic test. |
| • | A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail. |
| • | Use a scan tool to clear DTCs. |
| • | Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Clearing Diagnostic Trouble Codes in PCM Description and Operation. |
Diagnostic Aids
If this DTC set without a driveability complaint look for an open between splice and PCM or poor PCM terminal contact. If a complaint did exist look for poor relay contact, relay ground, etc.
Test Descriptions
-
When checking for circuit continuity (opens) resistance of 5 ohms or less indicates a good circuit.
When checking for shorts to ground, resistance of more than 10K ohms is usually acceptable although most readings should be infinite (OL).
-
The fuel pump fuse is powered by an ignition relay.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | |
2 |
Does engine start and run? | -- | Go to Step 3 | Go to Step 7 |
3 | On scan tool view the DTC status condition. Has this DTC failed this ignition cycle? | -- | Go to Step 4 | Fault not present. Refer to Diagnostic Aids |
4 | With engine still running in view FP. Volt Feedback. Is the voltage more than the value specified? | 2 volts | Go to Step 25 | Go to Step 5 |
5 |
Is the resistance the same or less than the value specified? | 5 ohms | Go to Step 25 | Go to Step 6 |
6 | Repair open in the Fuel Pump Feedback circuit between the PCM and the the Fuel Pump Feedback circuit splice or poor terminal contact at PCM connector C1 terminal 16. Is the repair complete? | -- | -- | |
7 | Check the condition of the Fuel Pump fuse. Is the fuse OK? | -- | Go to Step 8 | Go to Step 18 |
8 |
Is the voltage the same or more than the value specified? | 10 volts | Go to Step 9 | Go to Step 23 |
9 | Measure the voltage between fuel pump relay cavities 30 (B3) and 86 (A3). Is the voltage the same or more than the value specified? | 10 volts | Go to Step 10 | Go to Step 24 |
10 | Connect a jumper between fuel pump relay cavities 30 (B3) and 87 (A1). Does the fuel pump run or engine start? | -- | Go to Step 11 | Go to Step 15 |
11 |
Was the voltage the same or more than the value specified? | 10 volts | Go to Step 12 | Go to Step 13 |
12 | Replace the fuel pump relay. Is the repair complete? | -- | -- | |
Is the resistance measured within the values specified in the Test Description ? | -- | Go to Step 25 | Go to Step 14 | |
14 | Repair open or short to ground in the Fuel Pump Relay Control circuit. Is the repair complete? | -- | -- | |
15 | View FP. Volt Feedback on scan tool. Is the voltage the same or more than the value specified? | 10 volts | Go to Step 16 | Go to Step 17 |
16 |
Was a repair made to the Fuel Pump Feedback circuit? | -- | Go to Step 22 | |
17 | Repair open in the Fuel Pump Feedback circuit between fuel pump relay and splice. Is the repair complete? | -- | -- | |
18 |
Is the resistance more than the value specified? | 2 ohms | Go to Step 20 | Go to Step 19 |
19 | Repair short to ground in Fuel Pump Relay ignition feed circuit between the fuel pump fuse and relay. Is the repair complete? | -- | -- | |
20 |
Is the resistance more than the value specified? | 2 ohms | Go to Step 22 | Go to Step 21 |
21 | Repair short to ground in the Fuel Pump Feedback circuit between the PCM connector C1, the fuel pump connector, the fuel pump relay or a shorted fuel pump. Is the repair complete? | -- | -- | |
22 | Check fuel pump ground. Repair if needed. Was a repair made to the fuel pump ground circuit? | -- | ||
Repair the open in the Fuel Pump Relay ignition feed circuit between the fuse and relay or repair the loss of voltage to the fuse. Refer to Engine Electrical for repair of the voltage supply to the fuse. Is the repair complete? | -- | -- | ||
24 | Repair open in Fuel Pump Relay ground circuit or poor ground. Is the repair complete? | -- | -- | |
25 |
Was terminal contact repaired? | -- | Go to Step 26 | |
26 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the replacement complete? | -- | -- |
