
TEST ACTION APPLICABILITY
3 Turn the ignition off.
Disconnect the ECM harness connectors.
Using a 12-volt test light connected to 12-volts, check all of the ECM Ground circuits.
Does the test light illuminate brightly for each circuit?All
Ye s®Go To 4
No®Repair the Ground circuit(s) for high resistance.
Perform CHARGING VERIFICATION - VER-3.
4 Turn the ignition off.
Disconnect the ECM harness connectors.
Using a 12-volt test light connected to ground, check all of the ECM Battery Supply
circuits.
Does the test light illuminate brightly for each circuit?All
Ye s®Go To 5
No®Repair the Battery Supply circuit(s) for high resistance.
Perform CHARGING VERIFICATION - VER-3.
5WARNING: WHEN THE ENGINE IS OPERATING, DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR HANDS NEAR THE
PULLEYS, BELTS OR FAN. DO NOT WEAR LOOSE CLOTHING.
NOTE: The conditions that set the DTC are not present at this time. The
following list may help in identifying the intermittent condition.
With the engine running at normal operating temperature, monitor the DRB
parameters related to the DTC while wiggling the wiring harness. Look for param-
eter values to change and/or a DTC to set.
Review the DTC When Monitored and Set Conditions. If possible, try to duplicate the
conditions under which the DTC was set.
Refer to any Technical Service Bulletins (TSB) that may apply.
Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or
partially broken wires.
Visually inspect the related wiring harness connectors. Look for broken, bent, pushed
out, or corroded terminals.
Were any of the above conditions present?All
Ye s®Repair as necessary
Perform CHARGING VERIFICATION - VER-3.
No®Test Complete.
6 Turn the ignition off.
Disconnect ECM harness connectors.
Disconnect the Generator Field harness connector.
Measure the resistance between ground and the Generator Field Driver circuit.
Is the resistance above 100k ohms?All
Ye s®Go To 7
No®Repair the Generator Field Driver circuit for a short to ground.
Perform CHARGING VERIFICATION - VER-3.
11 8
DRIVEABILITY - DIESEL
P0560-SYSTEM VOLTAGE TOO HIGH ÐContinued

TEST ACTION APPLICABILITY
6WARNING: WHEN THE ENGINE IS OPERATING, DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR HANDS NEAR THE
PULLEYS, BELTS OR FAN. DO NOT WEAR LOOSE CLOTHING.
NOTE: The conditions that set the DTC are not present at this time. The
following list may help in identifying the intermittent condition.
With the engine running at normal operating temperature, monitor the DRB
parameters related to the DTC while wiggling the wiring harness. Look for param-
eter values to change and/or a DTC to set.
Review the DTC When Monitored and Set Conditions. If possible, try to duplicate the
conditions under which the DTC was set.
Refer to any Technical Service Bulletins (TSB) that may apply.
Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or
partially broken wires.
Visually inspect the related wiring harness connectors. Look for broken, bent, pushed
out, or corroded terminals.
Were any of the above conditions present?All
Ye s®Repair as necessary
Perform CHARGING VERIFICATION - VER-3.
No®Test Complete.
7 Turn the ignition off.
With a voltmeter, measure and record the voltage between the Battery terminals.
Disconnect the ECM harness connectors.
Turn the ignition on.
Measure the voltage of the Fuel Heater Relay Output circuit in the ECM C1 harness
connector.
Are the voltage measurements within 0.5 volt of each other?All
Ye s®Go To 8
No®Repair the Fuel Heater Relay Output circuit to the Engine
Control Module for high resistance.
Perform CHARGING VERIFICATION - VER-3.
8 Turn the ignition off.
Disconnect the ECM harness connectors.
Disconnect the Generator Field harness connector.
Remove the ECM/PCM Relay from the PDC.
Connect a jumper wire between cavity 30 and cavity 87 of the ECM/PCM Relay
connector.
Turn the ignition on.
Measure the voltage of the Generator Field Driver circuit.
Is the voltage below 0.5 volt?All
Ye s®Go To 9
No®Repair the Generator Field Driver circuit for a short to voltage.
Perform CHARGING VERIFICATION - VER-3.
122
DRIVEABILITY - DIESEL
P0560-SYSTEM VOLTAGE TOO LOW ÐContinued

TEST ACTION APPLICABILITY
4WARNING: WHEN THE ENGINE IS OPERATING, DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR HANDS NEAR THE
PULLEYS, BELTS OR FAN. DO NOT WEAR LOOSE CLOTHING.
NOTE: The conditions that set the DTC are not present at this time. The
following list may help in identifying the intermittent condition.
With the engine running at normal operating temperature, monitor the DRB
parameters related to the DTC while wiggling the wiring harness. Look for param-
eter values to change and/or a DTC to set.
Review the DTC When Monitored and Set Conditions. If possible, try to duplicate the
conditions under which the DTC was set.
Refer to any Technical Service Bulletins (TSB) that may apply.
Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or
partially broken wires.
Visually inspect the related wiring harness connectors. Look for broken, bent, pushed
out, or corroded terminals.
Were any of the above conditions present?All
Ye s®Repair as necessary.
Perform ROAD TEST VERIFICATION - VER-2.
No®Test Complete.
125
DRIVEABILITY - DIESEL
P0615-STARTER RELAY CIRCUIT SHORT CIRCUIT ÐContinued

TEST ACTION APPLICABILITY
4 Turn the ignition off.
Disconnect ECM harness connectors.
Disconnect the Generator Field harness connector.
Measure the resistance between ground and the Generator Field Control circuit.
Is the resistance above 100k ohms?All
Ye s®Go To 5
No®Repair the Generator Field Control circuit for a short to ground.
Perform CHARGING VERIFICATION - VER-3.
5 Turn the ignition off.
Disconnect the ECM harness connectors.
Disconnect the Generator Field harness connector.
Measure the resistance of the Generator Field Control circuit.
Is the resistance below 5.0 ohms?All
Ye s®Go To 6
No®Repair the Generator Field Control circuit for an open.
Perform CHARGING VERIFICATION - VER-3.
6 If there are no possible causes remaining, view repair. All
Repair
Replace and program the Engine Control Module in accordance
with the Service Information.
Perform CHARGING VERIFICATION - VER-3.
7WARNING: WHEN THE ENGINE IS OPERATING, DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR HANDS NEAR THE
PULLEYS, BELTS OR FAN. DO NOT WEAR LOOSE CLOTHING.
NOTE: The conditions that set the DTC are not present at this time. The
following list may help in identifying the intermittent condition.
With the engine running at normal operating temperature, monitor the DRB
parameters related to the DTC while wiggling the wiring harness. Look for param-
eter values to change and/or a DTC to set.
Review the DTC When Monitored and Set Conditions. If possible, try to duplicate the
conditions under which the DTC was set.
Refer to any Technical Service Bulletins (TSB) that may apply.
Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or
partially broken wires.
Visually inspect the related wiring harness connectors. Look for broken, bent, pushed
out, or corroded terminals.
Were any of the above conditions present?All
Ye s®Repair as necessary
Perform CHARGING VERIFICATION - VER-3.
No®Test Complete.
128
DRIVEABILITY - DIESEL
P0620-GENERATOR FIELD CONTROL MALF BATTERY VOLTAGE DEVI-
ATION TOO HIGH Ð
Continued

Symptom:
P0627-FUEL LIFT PUMP RELAY CONTROL CIRCUIT OPEN CIR-
CUIT
POSSIBLE CAUSES
INTERMITTENT CONDITION
IGNITION SWITCH (RUN/START) CIRCUIT OPEN
FUEL LIFT PUMP RELAY
FUEL LIFT PUMP RELAY CONTROL CIRCUIT SHORTED TO GROUND
FUEL LIFT PUMP RELAY CONTROL CIRCUIT OPEN
ENGINE CONTROL MODULE
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRB, actuate the Fuel Lift Pump Relay.
Does the Fuel Lift Pump Relay cycle on and off?All
Ye s®Go To 2
No®Go To 3
2WARNING: WHEN THE ENGINE IS OPERATING, DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR HANDS NEAR THE
PULLEYS, BELTS OR FAN. DO NOT WEAR LOOSE CLOTHING.
NOTE: The conditions that set the DTC are not present at this time. The
following list may help in identifying the intermittent condition.
With the engine running at normal operating temperature, monitor the DRB
parameters related to the DTC while wiggling the wiring harness. Look for param-
eter values to change and/or a DTC to set.
Review the DTC When Monitored and Set Conditions. If possible, try to duplicate the
conditions under which the DTC was set.
Refer to any Technical Service Bulletins (TSB) that may apply.
Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or
partially broken wires.
Visually inspect the related wiring harness connectors. Look for broken, bent, pushed
out, or corroded terminals.
Were any of the above conditions present?All
Ye s®Repair as necessary.
Perform ROAD TEST VERIFICATION - VER-2.
No®Test Complete.
3 Turn the ignition off.
Remove the Fuel Lift Pump Relay from the IPM.
Turn the ignition on.
Using a 12-volt test light connected to ground, check the Ignition Switch (RUN/
START) circuit.
Did the test light illuminate brightly?All
Ye s®Go To 4
No®Repair the Ignition Switch (RUN/START) circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
129
DRIVEABILITY - DIESEL

Symptom:
P0627-FUEL LIFT PUMP RELAY CONTROL CIRCUIT SHORT CIR-
CUIT
POSSIBLE CAUSES
INTERMITTENT CONDITION
FUEL LIFT PUMP RELAY
FUEL LIFT PUMP RELAY CONTROL CIRCUIT SHORTED TO VOLTAGE
ENGINE CONTROL MODULE
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRB, actuate the Fuel Lift Pump Relay.
Does the Fuel Lift Pump Relay cycle on and off?All
Ye s®Go To 2
No®Go To 3
2WARNING: WHEN THE ENGINE IS OPERATING, DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR HANDS NEAR THE
PULLEYS, BELTS OR FAN. DO NOT WEAR LOOSE CLOTHING.
NOTE: The conditions that set the DTC are not present at this time. The
following list may help in identifying the intermittent condition.
With the engine running at normal operating temperature, monitor the DRB
parameters related to the DTC while wiggling the wiring harness. Look for param-
eter values to change and/or a DTC to set.
Review the DTC When Monitored and Set Conditions. If possible, try to duplicate the
conditions under which the DTC was set.
Refer to any Technical Service Bulletins (TSB) that may apply.
Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or
partially broken wires.
Visually inspect the related wiring harness connectors. Look for broken, bent, pushed
out, or corroded terminals.
Were any of the above conditions present?All
Ye s®Repair as necessary.
Perform ROAD TEST VERIFICATION - VER-2.
No®Test Complete.
3 Turn the ignition off.
Install a substitute relay in place of the Fuel Lift Pump Relay.
Turn the ignition on.
With the DRB, actuate the Fuel Lift Pump Relay.
Does the Fuel Lift Pump Relay cycle on and off?All
Ye s®Replace the Fuel Lift Pump Relay.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 4
131
DRIVEABILITY - DIESEL

TEST ACTION APPLICABILITY
5 Turn the ignition off.
Disconnect the Accelerator Pedal Position Sensor harness connector.
Disconnect the ECM harness connectors.
Remove the ECM/PCM Relay from the IPM.
Connect a jumper wire between cavity 30 and cavity 87 of the ECM/PCM Relay
connector.
Turn the ignition on.
Measure the voltage on the Accelerator Pedal Position Sensor 5-Volt Supply circuit.
Is the voltage below 1.0 volt?All
Ye s®Go To 6
No®Repair the Accelerator Pedal Position Sensor 5-Volt Supply circuit
for a short to voltage.
Perform ROAD TEST VERIFICATION - VER-2.
NOTE: Remove the jumper wire and reinstall the ECM/PCM Relay.
6 If there are no possible causes remaining, view repair. All
Repair
Replace and program the Engine Control Module in accordance
with the Service Information.
Perform ROAD TEST VERIFICATION - VER-2.
7WARNING: WHEN THE ENGINE IS OPERATING, DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR HANDS NEAR THE
PULLEYS, BELTS OR FAN. DO NOT WEAR LOOSE CLOTHING.
NOTE: The conditions that set the DTC are not present at this time. The
following list may help in identifying the intermittent condition.
With the engine running at normal operating temperature, monitor the DRB
parameters related to the DTC while wiggling the wiring harness. Look for param-
eter values to change and/or a DTC to set.
Review the DTC When Monitored and Set Conditions. If possible, try to duplicate the
conditions under which the DTC was set.
Refer to any Technical Service Bulletins (TSB) that may apply.
Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or
partially broken wires.
Visually inspect the related wiring harness connectors. Look for broken, bent, pushed
out, or corroded terminals.
Were any of the above conditions present?All
Ye s®Repair as necessary.
Perform ROAD TEST VERIFICATION - VER-2.
No®Test Complete.
135
DRIVEABILITY - DIESEL
P0641-SENSOR REFERENCE VOLTAGE A CKT VOLTAGE TOO HIGH Ð
Continued

TEST ACTION APPLICABILITY
5 Turn the ignition off.
Disconnect the ECM harness connectors.
Disconnect the Fuel Pressure Sensor harness connector.
Measure the resistance between ground and the Fuel Pressure Sensor 5-Volt Supply
circuit.
Disconnect the Accelerator Pedal Position Sensor harness connector.
Measure the resistance between ground and the Accelerator Pedal Position Sensor
5-Volt Supply circuit.
Is the resistance above 100k ohms for each measurement?All
Ye s®Go To 6
No®Repair the 5-Volt Supply circuit(s) that measured less than 100k
ohms for a short to ground.
Perform ROAD TEST VERIFICATION - VER-2.
6 Turn the ignition off.
Disconnect the ECM harness connectors.
Disconnect the Fuel Pressure Sensor harness connector.
Measure the resistance between the Fuel Pressure Sensor 5-Volt Supply circuit and
the Sensor Ground circuit.
Disconnect the Accelerator Pedal Position Sensor harness connector.
Measure the resistance between the Accelerator Pedal Position Sensor 5-Volt Supply
circuit and the Sensor Ground circuit.
Is the resistance above 100k ohms for each measurement?All
Ye s®Go To 7
No®Repair the 5-Volt Supply circuit(s) that measured less than 100k
ohms for a short to the Sensor Ground circuit.
Perform ROAD TEST VERIFICATION - VER-2.
7 If there are no possible causes remaining, view repair. All
Repair
Replace and program the Engine Control Module in accordance
with the Service Information.
Perform ROAD TEST VERIFICATION - VER-2.
8WARNING: WHEN THE ENGINE IS OPERATING, DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR HANDS NEAR THE
PULLEYS, BELTS OR FAN. DO NOT WEAR LOOSE CLOTHING.
NOTE: The conditions that set the DTC are not present at this time. The
following list may help in identifying the intermittent condition.
With the engine running at normal operating temperature, monitor the DRB
parameters related to the DTC while wiggling the wiring harness. Look for param-
eter values to change and/or a DTC to set.
Review the DTC When Monitored and Set Conditions. If possible, try to duplicate the
conditions under which the DTC was set.
Refer to any Technical Service Bulletins (TSB) that may apply.
Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or
partially broken wires.
Visually inspect the related wiring harness connectors. Look for broken, bent, pushed
out, or corroded terminals.
Were any of the above conditions present?All
Ye s®Repair as necessary.
Perform ROAD TEST VERIFICATION - VER-2.
No®Test Complete.
138
DRIVEABILITY - DIESEL
P0641-SENSOR REFERENCE VOLTAGE A CKT VOLTAGE TOO LOW Ð
Continued