Page 648 of 5267

When Monitored:
While the engine is running.
Set Condition:
Fuel level does not change by a calibrated amount over a calibrated amount oftime.
Possible Causes
EXTERNAL DAMAGE TO FUEL TANK
FUEL LEVEL SENSOR
INSIDE OF FUEL TANK OBSTRUCTED DAMAGED
INTERMITTENT CONDITION
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
Diagnostic Test
1.EXTERNAL DAMAGE TO FUEL TANK
Visually inspect the fuel tank for external damage.
Is the fuel tank damaged from the outside?
Ye s>>
Fix or replace the fuel tank.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
No>>
Go To 2
2.FUEL LEVEL SENSOR
Disconnect the wiring harness from the fuel level sensor.
NOTE: Check connectors - Clean/repair as necessary.
Remove the fuel level sensor from the fuel tank.
Does the fuel level float move freely?
Ye s>>
Go To 3
No>>
Replace the fuel level sensor.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
3.FUEL LEVEL SENSOR
Measure the resistance between the sensor (N4) signal circuit and (K900) return circuit while moving the sensor
float arm.
Does the resistance level change as you move the sensor arm?
Ye s>>
Go To 4
No>>
Replace the fuel level sensor.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
Page 650 of 5267
P0462-LOW VOLTAGE DETECTED AT THE FUEL LEVEL SENSOR
For a complete wiring diagramRefer to Section 8W.
Page 654 of 5267
P0463-HIGH VOLTAGE DETECTED AT THE FUEL LEVEL SENSOR
For a complete wiring diagramRefer to Section 8W.
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 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 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 666 of 5267
P0483-FAN SPEED
For a complete wiring diagramRefer to Section 8W.
Page 667 of 5267

When Monitored:
While the engine is running.
Set Condition:
The actual fan speed is less than 50 RPM or more than 6000 RPM.
Possible Causes
OTHER DTC’S
(K161) SIGNAL CIRCUIT SHORT TO (K668) 5-VOLT SUPPLY CIRCUIT
(K161) SIGNAL CIRCUIT OPEN FROM ECM TO FAN CLUTCH ASSEMBLY
(K668) 5-VOLT SUPPLY CKT OPEN FROM ECM HARNESS CONNECTOR TO FAN CLUTCH HARNESS
CONNECTOR
INTERMITTENT CONDITION
(K161) SIGNAL CIRCUIT SHORTED TO (690) RETURN IN THE HARNESS
(K161) SIGNAL CIRCUIT SHORTED TO VOLTAGE
(K161) SIGNAL CIRCUIT IN ECM SHORTED TO GROUND INSIDE ECM
(K161) SIGNAL CIRCUIT SHORTED TO VOLTAGE IN THE ECM
(K668) 5-VOLT SUPPLY CIRCUIT IN ECM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
Diagnostic Test
1.OTHER DTC’S PRESENT
With the scan tool, read DTCs.
Is DTC P0480 present?
Ye s>>
Repair other DTC’s first.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
No>>
Go To 2
2.FA N C L U T C H S H O R T E D
Disconnect the wiring harness from the fan clutch assembly.
NOTE: Check connectors - Clean/repair as necessary.
Measure the resistance between the signal circuit in the fan clutch assembly and the return circuit in the fan clutch
assembly.
Is the resistance less than 10 Ohms?
Ye s>>
Replace the fan clutch assembly.
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