Page 719 of 5267

When Monitored:
While the ignition is on
Set Condition:
The brake switch status is = to OFF and the not brake switch status is = to ON for a calibrated amount of
time..
Possible Causes
DAMAGED WIRING HARNESS OR CONNECTORS
BRAKE SWITCH CIRCUIT SHORTED TO GROUND (BRAKE SWITCH WILL ALWAYS BE OFF)
BRAKE SWITCH
ECM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
1.BRAKE SWITCH CIRCUIT SHORTED TO GROUND
Turn the ignition off.
Disconnect the brake switch connection. Inspect the pins and connector
for damage, corrosion, etc.
Disconnect the ECM connectors. Inspect the pins and connector for
damage, corrosion, etc.
NOTE: Check connectors - Clean/repair as necessary.
Measure the resistance between the brake switch circuit in the ECM
connector and battery negative.
Is the resistance less than 10 ohms?
Ye s>>
Repair the Brake switch circuit shorted to ground.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
No>>
Go To 2
Page 720 of 5267
2.BRAKE SWITCH CIRCUIT SHORTED TO OTHER CIRCUITS IN HARNESS
Measure the resistance between the brake switch wire in the ECM con-
nector and all other pins in the ECM connector.
Is the resistance less than 10 ohms?
Ye s>>
Repair or replace the harness.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
No>>
Go To 3
3.ECM
Reconnect the ECM connectors.
Measure the resistance between the brake switch circuit at the switch
connector and battery negative.
Is the resistance less than 10 ohms?
Ye s>>
Replace the ECM.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
No>>
Go To 4
Page 723 of 5267

When Monitored:
While the ignition is on.
Set Condition:
The brake switch status is = to ON and the not brake switch status is = to OFF for a calibrated amount of time.
Possible Causes
DAMAGED WIRING HARNESS OR CONNECTORS
BRAKE SWITCH CIRCUIT OPEN (BRAKE SWITCH WILL ALWAYS BE ON)
BRAKE SWITCH CIRCUIT SHORTED TO BATTERY VOLTAGE (BRAKE SWITCH WILL ALWAYSBE ON)
BRAKE SWITCH
ECM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
1.BRAKE SWITCH CIRCUIT OPEN
Turn the ignition off.
Disconnect the brake switch connection. Inspect the pins and connector
for damage, corrosion, etc.
Disconnect the ECM connectors. Inspect the pins and connector for
damage, corrosion, etc.
NOTE: Check connectors - Clean/repair as necessary.
Measure the resistance between the brake switch signal circuits in the
ECM connector and the brake switch connector.
Is the resistance less than 10 ohms?
Ye s>>
Go To 2
No>>
Repair the open brake switch circuits.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
Page 724 of 5267

2.BRAKE SWITCH CIRCUIT SHORTED TO VOLTAGE
Measure the voltage between the brake switch circuits in the ECM con-
nector and battery negative.
Is the voltage less than 1 volt?
Ye s>>
Go To 3
No>>
Repair the open circuit.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
3.ECM
Reconnect the ECM connectors.
Install a jumper wire in the brake switch connector between signal circuitand to ground.
Turn the ignition on.
Cycle the brake pedal several times.
Using the scan tool, read the DTC’s.
Is the DTC for brake switch low voltage present?
Ye s>>
Go To 4
No>>
Replace the ECM.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
4.BRAKE SWITCH
Reconnect the brake switch connector.
Using the scan tool, clear the DTC’s.
Turn the ignition on.
Cycle the brake pedal several times.
Using the scan tool, read the DTC’s.
Has the brake switch High DTC returned?
Ye s>>
Replace the brake switch.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
No>>
Perform Intermittent condition test. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)
Page 739 of 5267
When Monitored:
When the ignition is on.
Set Condition:
The feedback signal does not match the commanded signal for the voltage regulator.
Possible Causes
GENERATOR
OPEN DRIVER CIRCUIT
GEN SOURCE SHORTED TO BATTERY NEGATIVE
(K20) FIELD DRIVER CIRCUIT SHORTED TO VOLTAGE
GEN SOURCE OPEN
ECM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
Diagnostic Test
1.GENERATOR
Turn the ignition off.
Disconnect the Generator field harness connector.
Check connectors - Clean/repair as necessary.
Measure the resistance between the generator field terminals.
Is the resistance between .5 and 15 Ohms?
Ye s>>
Go To 2
No>>
Replace the Generator.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
Page 740 of 5267
2.OPEN DRIVER CIRCUIT
Disconnect the ECM harness connectors.
Check connectors - Clean/repair as necessary.
Measure the resistance of the generator driver wire between the gener-
ator harness connector and the ECM harness connector.
Is the resistance less than 10 ohms.
Ye s>>
Go To 3
No>>
Repair the open driver circuit.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
3.GENERATOR FIELD CIRCUIT OPEN
Measure the resistance of the generator field return circuit between the
generator harness connector and battery negative.
Is the resistance less than 10 ohms.
No>>
Repair the Generator field return shorted to Battery nega-
tive.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
Ye s>>
Go To 4
Page 741 of 5267
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?
Ye s>>
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?
Ye s>>
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)
Page 743 of 5267

When Monitored:
Whilethekeyison.
Set Condition:
The commanded signal to the fuel lift pump circuit in the TIPM does not matchthe feedback signal from the
fuel lift pump circuit.
Possible Causes
WIRING HARNESS
TIPM
FUEL LIFT PUMP CONTROL CIRCUIT SHORTED TO EXTERNAL VOLTAGE
FUEL LIFT PUMP CONTROL CIRCUIT OPEN
FUEL LIFT PUMP GROUND CIRCUIT OPEN
FUEL LIFT PUMP 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.POWER AT TPIM
Using a voltmeter, measure the voltage on the Battery Supply wire to the TIPM.
Turn the ignition on, engine off.
Does the voltmeter show battery voltage?
No>>
Fix or replace the open circuit in the Battery Supply Circuit.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
Ye s>>
Go To 2
2.DAMANGED WIRING HARNESS
Turn Ignition off.
Disconnect the ECM and TIPM connectors. Inspect the connectors for signs of damage or corrosion.
NOTE: Check connectors - Clean/repair as necessary.
Are any pins damaged?
Ye s>>
Fix or replace the harness
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
No>>
Go To 5
3.FUEL LIFT PUMP CONTROL CIRCUIT OPEN
Using an ohmmeter, measure the resistance of the lift pump control circuitbetween the ECM connector and the
TIPM connector.
Is the resistance less than 10 Ohms?
Ye s>>
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)