Refer to Engine Controls Schematics
Fuel Pump Controls
.
Circuit Description
The status of the fuel lift pump is monitored by the PCM. This signal is also used in order to store a DTC if the fuel pump relay is defective or if the fuel lift pump voltage is lost while the engine is running. There should be approximately 12 volts on circuit 120 during the glow plug cycle.
Conditions for Running the DTC
The fuel lift pump is commanded ON.
Conditions for Setting the DTC
| • | The difference between the ignition voltage and the fuel lift pump voltage is more than 4 volts. |
| • | The condition was met for 2 seconds. |
Action Taken When the DTC Sets
| • | The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive drive trip the diagnostic runs and fails. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the Failure Records store this information. If the diagnostic reports a failure on the second consecutive drive trip, the Freeze Frame records the operating conditions at the time of failure and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn the MIL off after 3 consecutive trips without a fault condition. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures. |
| • | The scan tool Clear Info function was used. |
Diagnostic Aids
This DTC will not check the fuel lift pump for operation.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step checks if the PCM is sending a signal to turn the fuel lift pump ON. The scan tool display Lift Pump Voltage will indicate if the feed back voltage is being sent back to the PCM.
-
This step ensures that the replacement PCM, which utilizes an electrically erasable programmable read only memory (EEPROM), is programmed when installed.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 |
Important: Before clearing the DTCs, use the scan tool Capture Info to save the Freeze Frame and Failure Records for reference. The data in the control module is deleted once the Clear Info function is used. Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||
Does the scan tool indicate the fuel lift pump voltage is near the specified value? | B+ | Go to Diagnostic Aids | ||
3 |
Does the scan tool display voltage at the specified value? | B+ | ||
4 |
Is the test lamp ON? | -- | ||
5 |
Did you perform a repair? | -- | ||
6 | Connect a unpowered test lamp between terminal number B1 and terminal number A1 of the fuel pump relay harness connector. Is the test lamp ON? | -- | ||
7 | Repair the open fuel pump relay ground circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
8 | Repair the open in the battery feed circuit to the fuel pump relay. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
Does the unpowered test lamp come ON during the glow plug cycle and then go OFF after the glow plug cycle is complete? | -- | |||
10 |
Does the unpowered test lamp come ON during the glow plug cycle and then go OFF after the glow plug cycle is complete? | -- | ||
11 | Check for an open or short to ground in the control circuit from the fuel pump relay harness connector terminal number B3 and the PCM. Was a problem found? | -- | ||
12 | Repair the open or short to ground in the fuel pump relay control circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
13 |
Did you perform a repair? | -- | ||
|
Important: The new PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||
15 | Check for faulty connections at the fuel pump relay connector. Repair as necessary. Refer to Wiring Repairs in Wiring Systems. Did you perform a repair? | -- | ||
16 | Replace the fuel pump relay. Refer to Fuel Pump Relay Replacement . Is the action complete? | -- | -- | |
17 |
Does the scan tool indicate the diagnostic Passed? | -- | ||
18 | Does the scan tool display any additional undiagnosed DTCs? | -- | Go to the applicable DTC table | System OK |
