
TEST ACTION APPLICABILITY
4 Turn the ignition off.
Install a substitute relay in place of the Fuel Heater Relay.
Disconnect the ECM harness connectors.
Turn the ignition on.
Using a 12-volt test light connected to ground, check the Fuel Heater Relay Output
circuit.
Is the test light on?All
Ye s®Replace the initial Fuel Heater Relay.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 5
5 Turn the ignition off.
Disconnect the ECM harness connectors.
Disconnect the Crankcase Vent Heater harness connector.
Disconnect the Fuel Heater harness connector.
Remove the Fuel Heater Relay from the IPM.
Measure the resistance between ground and the Battery(+) Sense circuit.
Is the resistance above 100k ohms?All
Ye s®Go To 6
No®Repair the Battery(+) Sense circuit for a short to ground.
Perform ROAD TEST VERIFICATION - VER-2.
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 and 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.
165
DRIVEABILITY - DIESEL
P1511-BATTERY SENSE LINE 1 VOLTAGE TOO LOW ÐContinued

Symptom:
*CHECKING THE A/C CLUTCH OPERATION
POSSIBLE CAUSES
CHECK THE A/C CLUTCH OPERATION
FUSED B+ CIRCUIT OPEN
A/C CLUTCH RELAY
A/C CLUTCH RELAY OUTPUT CIRCUIT SHORTED TO VOLTAGE
A/C CLUTCH RELAY OUTPUT CIRCUIT SHORTED TO GROUND
A/C CLUTCH RELAY OUTPUT CIRCUIT OPEN
A/C CLUTCH GROUND CIRCUIT OPEN
A/C CLUTCH
TEST ACTION APPLICABILITY
1NOTE: Ensure that the refrigerant system is properly charged. Refer to the
appropriate Service Information.
Turn the ignition on.
With the DRBIIIt, actuate the A/C Clutch Relay.
Is the A/C Clutch actuating?All
Ye s®The A/C Clutch System is operating properly at this time.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 2
2NOTE: If the A/C Clutch fuse is open, refer to the system schematics for all
circuits that are powered by the A/C Clutch fuse to determine the cause of
the blown fuse.
Turn the ignition off.
Remove the A/C Clutch Relay from the IPM.
Using a 12-volt test light connected to ground, probe the Fused B+ circuit in the IPM.
Does the test light illuminate brightly?All
Ye s®Go To 3
No®Repair the Fused B+ circuit. Inspect fuse and replace as neces-
sary.
Perform ROAD TEST VERIFICATION - VER-2.
3 Turn the ignition off.
Install a substitute relay in place of the A/C Clutch Relay.
Turn the ignition on.
With the DRBIIIt, actuate the A/C Clutch Relay.
Does the A/C Clutch Relay cycle on and off?All
Ye s®Replace the A/C Clutch Relay.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 4
179
DRIVEABILITY - DIESEL

TEST ACTION APPLICABILITY
4 Turn the ignition off.
Remove the A/C Clutch Relay from the IPM.
Disconnect the A/C Clutch harness connector.
Measure the voltage of the A/C Clutch Relay Output circuit.
Is the voltage above 1.0 volt?All
Ye s®Repair the A/C Clutch Relay Output circuit for a short to voltage.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 5
5 Turn the ignition off.
Remove the A/C Clutch Relay from the IPM.
Disconnect the A/C Clutch harness connector.
Measure the resistance between ground and the A/C Clutch Relay Output circuit.
Is the resistance above 100k ohms?All
Ye s®Go To 6
No®Repair the A/C Clutch Relay Output circuit for a short to ground.
Inspect fuse and replace as necessary.
Perform ROAD TEST VERIFICATION - VER-2.
6 Turn the ignition off.
Remove the A/C Clutch Relay from the IPM.
Disconnect the A/C Clutch harness connector.
Measure the resistance of the A/C Clutch Relay Output circuit.
Is the resistance below 5.0 ohms?All
Ye s®Go To 7
No®Repair the A/C Clutch Relay Output circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
7 Turn the ignition off.
Disconnect the A/C Clutch harness connector.
Using a 12-volt test light connected to 12-volts, check the A/C Clutch Ground circuit.
Does the test light illuminate brightly?All
Ye s®Go To 8
No®Repair the A/C Clutch Ground circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
8 If there are no possible causes remaining, view repair. All
Repair
Replace the A/C Clutch.
Perform ROAD TEST VERIFICATION - VER-2.
180
DRIVEABILITY - DIESEL
*CHECKING THE A/C CLUTCH OPERATION ÐContinued

Symptom:
*CHECKING THE ECM POWER AND GROUND CIRCUITS
POSSIBLE CAUSES
ECM GROUND CIRCUIT(S) OPEN
ECM/PCM RELAY OUTPUT CIRCUIT(S) OPEN
FUSED ECM/PCM RELAY BATTERY SUPPLY CIRCUIT OPEN
FUSED IGNITION SWITCH OUTPUT CIRCUIT OPEN
TEST ACTION APPLICABILITY
1 Turn the ignition off.
Disconnect the ECM harness connectors.
Using a 12-volt test light connected to 12-volts, check both of the ECM ground
circuits in ECM harness connector C1 cavities 1 and 2.
Did the test light illuminate for both cavities?All
Ye s®Go To 2
No®Repair the ECM Ground circuit(s) for an open.
Perform ROAD TEST VERIFICATION - VER-2.
2 Turn the ignition off.
Disconnect the ECM harness connectors.
Turn the ignition on.
Using a 12-volt test light connected to ground, check the Fused Ignition Switch
Output circuit in ECM harness connector C1 cavity 22.
Is the test light on?All
Ye s®Go To 3
No®Repair the Fused Ignition Switch Output circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
3 Turn the ignition off.
Remove the ECM/PCM Relay from the IPM.
Using a 12-volt test light connected to ground, check the Fused ECM/PCM Relay
Battery Supply circuit in ECM/PCM Relay connector cavity 30.
Is the test light on?All
Ye s®Go To 4
No®Repair the Fused ECM/PCM Relay Battery Supply circuit for an
open.
Perform ROAD TEST VERIFICATION - VER-2.
183
DRIVEABILITY - DIESEL

TEST ACTION APPLICABILITY
4 Turn the ignition off.
Disconnect the ECM harness connectors.
Remove the ECM/PCM Relay from the IPM.
Connect a jumper wire between cavity 30 and cavity 87 in the ECM/PCM Relay
connector.
Using a 12-volt test light connected to ground, check the ECM/PCM Relay Output
circuit in ECM harness connector C1 cavities 4 and 5.
Did the test light illuminate for both circuits?All
Ye s®Test Complete.
No®Repair the ECM/PCM Relay Output circuit(s) for an open.
Perform ROAD TEST VERIFICATION - VER-2.
184
DRIVEABILITY - DIESEL
*CHECKING THE ECM POWER AND GROUND CIRCUITS ÐContinued

Symptom:
*CHECKING THE EGR SYSTEM
POSSIBLE CAUSES
ECM/PCM RELAY OUTPUT CIRCUIT OPEN
EGR SOLENOID CONTROL CIRCUIT OPEN
EGR VALVE
VACUUM SUPPLY HOSE
TEST ACTION APPLICABILITY
1 Disconnect the Vacuum Supply Hose at the EGR solenoid.
Connect a vacuum gauge to the Vacuum Supply Hose.
Start the engine and allow the engine to idle.
Is the vacuum above 10 inches of mercury at idle?All
Ye s®Go To 2
No®Repair leaking or restricted Vacuum Supply Hose or faulty
Vacuum Supply Pump.
Perform ROAD TEST VERIFICATION - VER-2.
2 Turn the ignition off.
Disconnect the EGR Solenoid harness connector.
Turn the ignition on.
Using a 12-volt test light connected to ground, check the ECM/PCM Relay Output
circuit at the EGR Solenoid harness connector.
Is the test light on?All
Ye s®Go To 3
No®Repair the ECM/PCM Relay Output circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
3 Turn the ignition off.
Disconnect the EGR Solenoid harness connector.
Disconnect the ECM harness connectors.
Measure the resistance of the EGR Solenoid Control circuit.
Is the resistance below 10.0 ohms?All
Ye s®Go To 4
No®Repair the EGR Solenoid Control circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
4NOTE: The Vacuum Output Hose must not be leaking or restricted for the
result of this test to be valid.
Turn the ignition off.
Disconnect the Vacuum Supply and Vacuum Output Hoses in the EGR Solenoid
vacuum connector.
Connect the Vacuum Supply Hose to the Vacuum Output Hose.
Test drive the vehicle and observe vehicle performance.
Is there a power reduction on vehicle acceleration?All
Ye s®Test Complete.
No®Replace the EGR Valve.
Perform ROAD TEST VERIFICATION - VER-2.
185
DRIVEABILITY - DIESEL

TEST ACTION APPLICABILITY
6 Turn the ignition on.
With the DRB, actuate the Low Speed Rad Fan and observe the Radiator Fans.
NOTE: Both Radiator Fans should operate at low speed.
Did both Radiator Fans operate as they should?All
Ye s®Go To 7
Fans do not operate on Low
Go To 15
Fan 1 on High/Fan 2 not on
Go To 23
Fan 1 not on/Fan 2 on High
Go To 26
7 Turn the ignition on.
With the DRB, actuate the High and Low Speed Rad Fans at the same time and
observe the Radiator Fans.
NOTE: Both Radiator Fans should operate at high speed.
Did both Radiator Fans operate as they should?All
Ye s®The test is complete. Ensure the ECM will turn the fans on when
the engine is hot.
Perform ROAD TEST VERIFICATION - VER-2.
Fan 1 on High/Fan 2 not on
Go To 8
Fan 1 not on/Fan 2 on High
Go To 11
8 Turn the ignition off.
Disconnect the Radiator Fan Relay No. 2 harness connector.
Using a 12-volt test light connected to ground, check the Fused B+ circuit.
Did the test light illuminate brightly?All
Ye s®Go To 9
No®Repair the Radiator Fan Relay No. 2 Fused B+ circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
9 Turn the ignition off.
Install a substitute relay in place of Radiator Fan Relay No. 2.
Turn the ignition on.
With the DRB, actuate the High Speed Fan Relay.
Does Radiator Fan No. 2 cycle on and off?All
Ye s®Replace Radiator Fan Relay No. 2.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 10
188
DRIVEABILITY - DIESEL
*CHECKING THE ELECTRIC RADIATOR FAN OPERATION ÐContinued

TEST ACTION APPLICABILITY
10 Turn the ignition off.
Disconnect the Radiator Fan Relay No. 2 harness connector.
Disconnect the Radiator Fan No. 2 harness connector.
Measure the resistance of the Radiator Fan Relay No. 2 and No. 3 Common Output
circuit from Radiator Fan Relay No. 2.
Is the resistance below 5.0 ohms?All
Ye s®Test Complete.
No®Repair the Radiator Fan Relay No. 2 and No. 3 Common Output
circuit from Radiator Fan Relay No. 2 for an open.
Perform ROAD TEST VERIFICATION - VER-2.
11 Turn the ignition off.
Disconnect the Radiator Fan Relay No. 3 harness connector.
Using a 12-volt test light connected to ground, check the Fused B+ circuit.
Did the test light illuminate brightly?All
Ye s®Go To 12
No®Repair the Radiator Fan Relay No. 3 Fused B+ circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
12 Turn the ignition off.
Install a substitute relay in place of Radiator Fan Relay No. 3.
Turn the ignition on.
With the DRB, actuate the High Speed Fan Relay and then actuate the Low Speed
Fan Relay.
Does Radiator Fan No. 2 cycle on and off and then both fans cycle on and off when
requested?All
Ye s®Replace Radiator Fan Relay No. 3.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 13
13 Turn the ignition off.
Disconnect the Radiator Fan Relay No. 3 harness connector.
Disconnect the Radiator Fan No. 2 harness connector.
Using a 12-volt test light connected to 12-volts, check the Radiator Fan Relay No. 3
Ground circuit at the Radiator Fan Relay No. 3 harness connector.
Did the test light illuminate brightly?All
Ye s®Go To 14
No®Repair the Radiator Fan Relay No. 3 Ground circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
14 Turn the ignition off.
Disconnect the Radiator Fan Relay No. 3 harness connector.
Disconnect the ECM harness connectors.
Measure the resistance of the High Speed Radiator Fan Dual Relay Control circuit.
Is the resistance below 5.0 ohms?All
Ye s®Test Complete.
No®Repair the High Speed Radiator Fan Dual Relay Control circuit
for an open.
Perform ROAD TEST VERIFICATION - VER-2.
189
DRIVEABILITY - DIESEL
*CHECKING THE ELECTRIC RADIATOR FAN OPERATION ÐContinued