Page 657 of 5267

P0477-LOW VOLTAGE ON THE ENGINE BRAKE DRIVER
For a complete wiring diagramRefer to Section 8W.
When Monitored:
When the ignition is on.
Set Condition:
When the signal from the engine brake driver output does not match the signal from the engine brake driver
feedback.
Possible Causes
WIRING HARNESS
ENGINE BRAKE DRIVER RELAY
FUSED B+ OPEN
ENGINE BRAKE DRIVER SIGNAL CIRCUIT OPEN
INTERMITTENT CONDITION
ENGINE BRAKE DRIVER SIGNAL CIRCUIT SHORTED TO BATTERY NEGATIVE
ECM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
Diagnostic Test
1.RELAY CLICKING
Turn the engine off (ignition on).
With the scan tool, actuate the exhaust brake relay.
Can you hear the Relay clicking?
Ye s>>
Go To 2
No>>
Go To 3
2.WIRING HARNESS
With the scan tool, actuate the exhaust brake relay.
While the relay is clicking, wiggle the wiring harness and connectors throughout the circuit.
Does this interrupt the clicking?
Ye s>>
Repair or replace the wiring 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 3
3.Engine Brake Driver Relay
Remove the Engine Brake Driver Relay.
Check connectors - Clean/repair as necessary.
Measure the resistance between terminals 86 and 85 of the engine brake relay.
Is the resistance less than 100 Ohms?
Ye s>>
Go To 4
No>>
Replace the Engine Brake Driver Relay.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
Page 658 of 5267

4.FUSED B+ OPEN
Ignition on, engine not running.
Measure the voltage of the Fused B+ Supply circuit at the Engine Brake Relay.
Is the voltage within 10% of battery voltage?
Ye s>>
Go To 5
No>>
Repair the open B+ circuit.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
5.ENGINE BRAKE DRIVER SIGNAL CIRCUIT OPEN
Turn the ignition off.
Disconnect the ECM harness connectors.
Check connectors - Clean/repair as necessary.
Measure the resistance of the Engine Brake Driver signal circuit between the Relay harness connector and the ECM
harness connector.
Is the resistance less than 10 Ohms?
Ye s>>
Go To 6
No>>
Repair the open Engine Brake driver circuit open from relay to ECM.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
6.ENGINE BRAKE DRIVER SIGNAL CIRCUIT SHORTED TO BATTERY NEGATIVE
Measure the resistance of the Engine Brake Driver signal circuit between the Relay connector and battery negative.
Is the resistance greater than 100k Ohms?
Ye s>>
Go To 7
No>>
Repair Engine brake driver shorted to Battery negative.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
7.ECM
Reconnect the ECM harness connectors.
Using the scan tool, actuate the Engine Brake Driver Relay.
While monitoring with the scan tool, use a jumper wire to connect 12 volts tothe relay signal circuit with the relay
disconnected.
Did the DTC P0478?
Ye s>>
Refer to the INTERMITTENT CONDITION Symptom (Diagnostic Procedure). (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
No>>
Replace ECM.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
Page 659 of 5267

P0478-HIGH VOLTAGE ON THE ENGINE BRAKE DRIVER
For a complete wiring diagramRefer to Section 8W.
When Monitored:
When the ignition is on.
Set Condition:
When the signal from the engine brake driver output does not match the signal from the engine brake driver
feedback.
Possible Causes
RELAY LOOSE
ENGINE BRAKE DRIVER CONTROL CIRCUIT SHORTED TO VOLTAGE
ENGINE BRAKE RELAY
INTERMITTENT CONDITION
ECM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
Diagnostic Test
1.RELAY
Ignition on, engine not running.
With the scan tool, actuate the Engine Brake Driver Relay.
Can you hear the Relay clicking?
Ye s>>
Go To 2
No>>
Go To 3
2.RELAY LOOSE
While the relay is clicking, wiggle the wiring harness and connectors.
Does this interrupt the clicking?
Ye s>>
Repair the loose connection.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
No>>
Go To 3
3.Engine Brake Driver Control Circuit
Turn the ignition off.
Remove the Engine Brake Driver Relay.
Disconnect the ECM harness connectors.
Check connectors - Clean/repair as necessary.
Measure the voltage of the Engine Brake Driver Control Circuit between therelay terminal and battery negative.
Is the voltage less than 1 volt?
Ye s>>
Go To 4
No>>
Repair Engine Brake Driver Control 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)
Page 660 of 5267
4.Engine brake relay
Measure the resistance between terminals 85 and 86 of the engine brake relay.
Is the resistance less than 10 ohms?
Ye s>>
Replace the engine brake relay.
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
5.ECM
Reconnect the ECM harness connectors.
Reinstall the Engine Brake relay.
Ignition on, engine not running.
While monitoring with the scan tool, remove the Engine Brake Driver Relay.
Did P0477 set?
Ye s>>
Refer to the INTERMITTENT CONDITION Symptom (Diagnostic Procedure). (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
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)
Page 661 of 5267
P0480-FAN CLUTCH
For the Engine circuit diagram (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES/ENGINE CON-
TROL MODULE - SCHEMATIC - ELECTRICAL)
Page 662 of 5267

For a complete wiring diagramRefer to Section 8W.
When Monitored:
When the ignition is on.
Set Condition:
When the control coil is electrically shorted or open.
Possible Causes
FA N C L U TC H
WIRE HARNESS DAMAGED
OPEN FAN CLUTCH (K160) DRIVER CIRCUIT
(K160) DRIVER CIRCUIT SHORTED TO (K690) RETURN CIRCUIT
(K160) DRIVER CIRCUIT SHORTED TO BATTERY NEGATIVE
INTERMITTENT CONDITION
ECM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
Diagnostic Test
1.FA N C L U T C H
Disconnect the fan clutch harness connector.
Check connectors - Clean/repair as necessary.
Measure the resistance between the fan clutch (K160) driver circuit and
the fan speed (K690) sensor return circuit on the fan clutch assembly.
Is the resistance less than 10 Ohms?
Ye s>>
Replace the fan clutch.
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 663 of 5267

2.FA N C L U T C H
Disconnect the Fan Clutch harness connectors.
NOTE: Check connectors - Clean/repair as necessary.
Measure the resistance between the fan clutch (K160) driver circuit and
the fan clutch (F504) battery supply circuit on the fan clutch assembly.
Istheresistancelessthan6Ohmsorgreaterthan10Ohms?
Ye s>>
Replace the fan clutch.
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.OPEN FAN CLUTCH (K160) DRIVER CIRCUIT
Disconnect the ECM harness connectors.
Check connectors - Clean/repair as necessary.
Measure the resistance of the fan clutch (K160) driver circuit between
the ECM harness connector and the fan clutch harness connector.
Is the resistance less than 10 Ohms?
Ye s>>
Go To 4
No>>
Repair the open fan clutch (K160) river circuit.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
Page 664 of 5267
4.(K160) DRIVER CIRCUIT SHORTED TO (K690) RETURN CIRCUIT
Measure the resistance between the fan clutch (K160) driver circuit and
the fan speed sensor (K690) return circuit at the sensor harness con-
nector.
Is the resistance greater than 100K Ohms?
Ye s>>
Go To 5
No>>
Repair the (K160) Driver circuit shorted to (K690) Return
circuit.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
5.(K160) DRIVER CIRCUIT SHORTED TO BATTERY NEGATIVE
Measure the resistance between the fan clutch (K160) driver circuit and
the battery negative.
Is the resistance greater than 100k Ohms?
Ye s>>
Go To 6
No>>
Repair the (K160) Driver circuit shorted to battery negative.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)