Circuit Description
The status of the fuel pump is monitored by the powertrain control module (PCM). This signal is also used to store a diagnostic trouble code (DTC) if the fuel pump relay is defective or fuel pump voltage is lost while the engine is running. There should be about 12 volts on circuit 120 during glow plug cycle.
Conditions for Running the DTC
| • | The PCM performs this DTC diagnostic continuously. |
| • | The fuel lift pump is commanded ON. |
Conditions for Setting the DTC
| • | The difference between ignition voltage and fuel pump voltage is more than 4 volts. |
| • | All diagnostic conditions are met for 2 seconds. |
Action Taken When the DTC Sets
| • | The control module stores the DTC information into memory when the diagnostic runs and fails. |
| • | The malfunction indicator lamp (MIL) will not illuminate. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records. |
| • | The driver information center, if equipped, may display a message. |
Conditions for Clearing the DTC
| • | 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 non-emission related diagnostic. |
| • | Clear the DTC with a scan tool. |
Diagnostic Aids
This DTC will not check the fuel pump operation.
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
2 |
Does the scan tool indicate the fuel pump is operating? | -- | Go to Diagnostic Aids | Go to Step 3 |
Does the voltage measure the specified value? | B+ | Go to Step 8 | Go to Step 4 | |
4 |
Does the voltage measure the specified value? | B+ | Go to Step 5 | Go to Step 6 |
5 |
Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 18 |
6 |
Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 7 |
7 |
Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 16 |
8 |
Does the test lamp illuminate? | -- | Go to Step 10 | Go to Step 9 |
9 | Repair the open in the battery positive voltage circuit to the fuel pump relay. Did you complete the repair? | -- | Go to Step 19 | -- |
10 | Connect a test lamp the battery positive voltage circuit and ground circuit of the fuel pump relay harness connector. Does the test lamp illuminate? | -- | Go to Step 12 | Go to Step 11 |
11 | Repair the open fuel pump relay ground circuit. Did you complete the repair? | -- | Go to Step 19 | -- |
12 |
Does the test lamp illuminate during the glow plug cycle and go OFF after the glow plug cycle is complete? | -- | Go to Step 13 | Go to Step 14 |
13 |
Does the test lamp illuminate during the glow plug cycle and go OFF after the glow plug cycle is complete? | -- | Go to Step 16 | Go to Step 17 |
14 | Check for an open or short to ground in the fuel pump relay control circuit. Was a problem found? | -- | Go to Step 15 | Go to Step 16 |
15 | Repair the open or short to ground in the fuel pump relay control circuit. Did you complete the repair? | -- | Go to Step 19 | -- |
16 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 19 | -- |
17 | Check for proper connections at the fuel pump relay connector. Was a problem found? | -- | Go to Step 19 | Go to Step 18 |
18 | Replace the fuel pump relay with the Relay Puller Pliers. Did you complete the replacement? | -- | Go to Step 19 | -- |
19 |
Does the DTC run and pass? | -- | Go to Step 20 | Go to Step 2 |
20 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
