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
Symptom:
P0645-A/C CLUTCH RELAY CIRCUIT OPEN CIRCUIT
When Monitored and Set Condition:
P0645-A/C CLUTCH RELAY CIRCUIT OPEN CIRCUIT
When Monitored: With the ignition on.
Set Condition: The ECM detects an open or short to ground on the A/C Clutch Relay
Control circuit.
POSSIBLE CAUSES
A/C CLUTCH RELAY CONTROL CIRCUIT SHORT TO GROUND
A/C CLUTCH RELAY INTERMITTENT OPERATION
INTERMITTENT CONDITION
FUSED IGNITION SWITCH OUTPUT CIRCUIT OPEN
INTELLIGENT POWER MODULE
A/C CLUTCH RELAY
IPM FUSE & RELAY CENTER
A/C CLUTCH RELAY CONTROL CKT OPEN
ECM
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRBIIIt, actuate the A/C Clutch Relay.
Is the A/C Clutch Relay operating?All
Ye s®Go To 2
No®Go To 4
2 Turn the ignition on.
With the DRBIIIt, actuate the A/C Clutch Relay.
Wiggle the wiring harness from the A/C Clutch Relay to the ECM while the relay is
actuating.
Did the A/C Clutch Relay stop when wiggling the wiring harness?All
Ye s®Repair as necessary.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 3
139
DRIVEABILITY - DIESEL
TEST ACTION APPLICABILITY
3WARNING: KEEP CLEAR OF THE ENGINE'S MOVING PARTS.
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 DRB Freeze Frame information. 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.
4 Turn the ignition off.
Remove the A/C Clutch Relay from the IPM.
Turn the ignition on.
Using a 12-volt test light connected to ground, probe the Fused Ignition Switch
circuit in the IPM.
Does the test light illuminate?All
Ye s®Go To 5
No®Go To 10
5 Turn the ignition off.
Remove the A/C Clutch Relay from the IPM.
Turn the ignition on.
Using a 12-volt test light connected to 12-volts, probe the A/C Clutch Relay Control
circuit in the IPM.
With the DRBIIIt, actuate the A/C Clutch Relay.
Does the test light cycle on and off?All
Ye s®Replace the A/C Clutch Relay.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 6
6 Turn the ignition off.
Disconnect the Intelligent Power Module C3 harness connector.
Turn the ignition on.
Using a 12-volt test light connected to 12-volts, probe the A/C Clutch Relay Control
circuit in the IPM harness connector.
With the DRBIIIt, actuate the A/C Clutch Relay.
Does the test light flash on and off?All
Ye s®Replace the IPM Fused & Relay Center.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 7
140
DRIVEABILITY - DIESEL
P0645-A/C CLUTCH RELAY CIRCUIT OPEN CIRCUIT ÐContinued
Symptom:
P0645-A/C CLUTCH RELAY CIRCUIT SHORT CIRCUIT
When Monitored and Set Condition:
P0645-A/C CLUTCH RELAY CIRCUIT SHORT CIRCUIT
When Monitored: With the ignition on.
Set Condition: The ECM detects a short to voltage on the A/C Clutch Relay Control
circuit.
POSSIBLE CAUSES
A/C CLUTCH RELAY INTERMITTENT OPERATION
INTERMITTENT CONDITION
FUSED IGNITION SWITCH OUTPUT CIRCUIT OPEN
INTELLIGENT POWER MODULE
A/C CLUTCH RELAY
IPM FUSE & RELAY CENTER
A/C CLUTCH RELAY CONTROL CIRCUIT SHORTED TO VOLTAGE
ECM
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRBIIIt, actuate the A/C Clutch Relay.
Is the A/C Clutch Relay operating?All
Ye s®Go To 2
No®Go To 4
2 Turn the ignition on.
With the DRBIIIt, actuate the A/C Clutch Relay.
Wiggle the wiring harness from the A/C Clutch Relay to the ECM while the relay is
actuating.
Did the A/C Clutch Relay stop when wiggling the wiring harness?All
Ye s®Repair as necessary.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 3
142
DRIVEABILITY - DIESEL
TEST ACTION APPLICABILITY
3WARNING: KEEP CLEAR OF THE ENGINE'S MOVING PARTS.
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 DRB Freeze Frame information. 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.
4 Turn the ignition off.
Remove the A/C Clutch Relay from the IPM.
Turn the ignition on.
Using a 12-volt test light connected to ground, probe the Fused Ignition Switch
circuit in the IPM.
Does the test light illuminate?All
Ye s®Go To 5
No®Go To 9
5 Turn the ignition off.
Remove the A/C Clutch Relay from the IPM.
Turn the ignition on.
Using a 12-volt test light connected to 12-volts, probe the A/C Clutch Relay Control
circuit in the IPM.
With the DRBIIIt, actuate the A/C Clutch Relay.
Does the test light cycle on and off?All
Ye s®Replace the A/C Clutch Relay.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 6
6 Turn the ignition off.
Disconnect the Intelligent Power Module C3 harness connector.
Turn the ignition on.
Using a 12-volt test light connected to 12-volts, probe the A/C Clutch Relay Control
circuit in the IPM harness connector.
With the DRBIIIt, actuate the A/C Clutch Relay.
Does the test light flash on and off?All
Ye s®Replace the IPM Fused & Relay Center.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 7
143
DRIVEABILITY - DIESEL
P0645-A/C CLUTCH RELAY CIRCUIT SHORT CIRCUIT ÐContinued