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 with the engine cranking or running.
Conditions for Setting the DTC
Test Condition
Engine speed 24 RPM or greater.
Failure Condition
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.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to A Powertrain On Board Diagnostic (OBD) System Check | |
2 |
Does engine start and run? | -- | ||
3 | On scan tool note the DTC status condition. Has this DTC failed this ignition cycle? | -- | Fault not present. Refer to Diagnostic Aids | |
4 | With engine still running view FP. Volt Feedback on the scan tool. Is the voltage more than the value specified? | 2 volts | ||
5 |
Is the resistance the same or less than the value specified? | 5 ohms | ||
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? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
7 | Check the condition of the Fuel Pump fuse. Is the fuse OK? | -- | ||
8 |
Is the voltage the same or more than the value specified? | 10 volts | ||
9 | Measure the voltage between fuel pump relay cavities 30 and 86. Is the voltage the same or more than the value specified? | 10 volts | ||
10 | Connect a jumper between fuel pump relay cavities 30 and 87. Does the fuel pump run or engine start? | -- | ||
11 |
Was the voltage the same or more than the value specified? | 10 volts | ||
12 | Replace the fuel pump relay. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
Is the resistance measured within the values specified in the Test description? | -- | |||
14 | Repair open or short to ground in the Fuel Pump Relay Control circuit. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
15 | Check FP. Volt Feedback on scan tool. Is the voltage the same or more than the value specified? | 10 volts | ||
16 |
Was a repair made to the Fuel Pump Feedback circuit? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | |
17 | Repair open in the Fuel Pump Feedback circuit between fuel pump relay and splice. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
18 |
Is the resistance more than the value specified? | 2 ohms | ||
19 | Repair short to ground in Fuel Pump Relay ignition feed circuit between the fuel pump fuse and relay. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
20 |
Is the resistance more than the value specified? | 2 ohms | ||
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? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
22 | Check fuel pump ground. Repair if needed. Was a repair made to the fuel pump ground circuit? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | Go to Fuel Pressure Check |
23 | 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 Electrical Diagnosis for repair of the voltage supply to the fuse. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
24 | Repair open in Fuel Pump Relay ground circuit or poor ground. Is the repair complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
25 |
Was terminal contact repaired? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | |
26 | Replace the PCM. Refer to PCM Replacement/Programming . Is the replacement complete? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair | -- |
