Dodge Ram Truck 1500-2500-3500. Manual — part 1107

P0622-GENERATOR FIELD NOT SWITCHING PROPERLY (CONTINUED)

4.

FIELD DRIVER CIRCUIT SHORTED TO VOLTAGE

Measure the voltage between the (K20) generator field driver circuit in
the generator harness connector and battery negative.

Is the voltage greater than 1 volt?

Yes

>> Repair the (K20) Generator field driver circuit shorted to

voltage.

No

>> Go To 5

5.

ECM

While monitoring with scan tool, connect a jumper wire between the driver circuit and the return circuit in the alter-
nator connector.

Did the DTC return?

Yes

>> Replace the ECM.

Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)

No

>> Repair complete.

Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)

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ENGINE - ELECTRICAL DIAGNOSTICS - DIESEL

DR/DH

P0628-LOW VOLTAGE DETECTED AT THE FUEL LIFT PUMP

DR/DH

ENGINE - ELECTRICAL DIAGNOSTICS - DIESEL

9 - 1351

P0628-LOW VOLTAGE DETECTED AT THE FUEL LIFT PUMP (CONTINUED)

For the Engine circuit diagram (Refer to 9 - ENGINE - SCHEMATICS AND DIAGRAMS)

For a complete wiring diagram Refer to Section 8W.

•

When Monitored:
While the key is on.

•

Set Condition:
The commanded signal to the fuel lift pump relay does not match the feedback signal from the fuel lift pump
relay.

Possible Causes

WIRING HARNESS

FUEL LIFT PUMP RELAY

FUEL LIFT PUMP RELAY DRIVER CIRCUIT SHORTED TO EXTERNAL VOLTAGE

FUEL LIFT PUMP RELAY DRIVER CIRCUIT OPEN

FUEL LIFT PUMP RELAY GROUND CIRCUIT OPEN

FUEL LIFT PUMP RELAY GROUND CIRCUIT SHORTED TO EXTERNAL VOLTAGE

ECM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)

Diagnostic Test

1.

LIFT PUMP RUNS

Remove the cover to the PDC.

Turn the ignition on, engine off.

With the scan tool, in system test actuate the lift pump relay.

Does the fuel lift pump relay click when the lift pump is actuated?

Yes

>> Test complete.

Perform Intermittent Condition test. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

No

>> Go To 2

2.

LIFT PUMP RELAY DOES NOT CLICK

Turn Ignition off.

Remove the lift pump relay from the PDC.

Turn the ignition on.

Connect one end of an incandescent test light to battery negative.

Connect the other end of the test light to the relay driver pin in the PDC.

With the scan tool, in system test actuate the lift pump relay.

Does the test light illuminate brightly?

Yes

>> Go To 3

No

>> Go To 5

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ENGINE - ELECTRICAL DIAGNOSTICS - DIESEL

DR/DH

P0628-LOW VOLTAGE DETECTED AT THE FUEL LIFT PUMP (CONTINUED)

3.

FUEL LIFT PUMP GROUND CIRCUIT OPEN

Connect one end of an incandescent test light to battery postive.

Connect the other end of the test light to the relay ground pin in the PDC.

Is the resistance less than 1 Ohms?

Yes

>> Go To 4

No

>> Repair the open ground circuit.

Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)

4.

LIFT PUMP RELAY

Install a know good relay in place of the fuel lift pump relay.

With the scan tool, in system test actuate the lift pump relay.

Does the fuel lift pump relay click when the lift pump is actuated?

No

>> Go To 5

Yes

>> Replace the lift pump relay.

Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)

5.

FUEL LIFT PUMP DRIVER CIRCUIT OPEN

Turn Ignition off.

Disconnect the ECM connectors.

NOTE: Check connectors - Clean/repair as necessary.
Using an ohmmeter, measure the resistance of the lift pump relay driver wire between the ECM connector and the
PDC.

Is the resistance less than 10 Ohms?

No

>> Repair the Fuel lift pump driver circuit open.

Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)

Yes

>> Go To 6

6.

FUEL LIFT PUMP RELAY DRIVER CIRCUIT SHORTED TO EXTERNAL VOLTAGE

Measure the voltage between battery negative and the relay driver circuit in the PDC.

Is the voltage greater than 1 volt?

Yes

>> Repair the Fuel lift pump Relay driver circuit shorted to voltage.

Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)

No

>> Go To 7

DR/DH

ENGINE - ELECTRICAL DIAGNOSTICS - DIESEL

9 - 1353