Symptom:
*CHECKING THE ELECTRIC RADIATOR FAN OPERATION
POSSIBLE CAUSES
ACTUATE THE HIGH AND LOW SPEED RADIATOR FAN WITH THE DRB
CHECK FOR RADIATOR FAN RELAY CONTROL DTCS
RADIATOR FAN RELAY NO. 1 OUTPUT CIRCUIT SHORTED TO VOLTAGE
RADIATOR FAN RELAY NO. 2 AND NO. 3 COMMON OUTPUT CIRCUIT SHORTED TO VOLTAGE
RADIATOR FAN NO. 1 CONTROL CIRCUIT SHORTED TO VOLTAGE
RADIATOR FAN RELAY NO. 1 FUSED B+ CIRCUIT OPEN
RADIATOR FAN RELAY NO. 2 AND NO. 3 COMMON OUTPUT CIRCUIT SHORTED TO GROUND
RADIATOR FAN RELAY NO. 2 FUSED B+ CIRCUIT OPEN
RADIATOR FAN RELAY NO. 3 FUSED B+ CIRCUIT OPEN
RADIATOR FAN NO. 1 CONTROL CIRCUIT SHORTED TO GROUND
RADIATOR FAN RELAY NO. 1
RADIATOR FAN RELAY NO. 1 - INTERNAL SHORT TO VOLTAGE
RADIATOR FAN RELAY NO. 2
RADIATOR FAN RELAY NO. 2 OR NO. 3 - INTERNAL SHORT TO VOLTAGE
RADIATOR FAN RELAY NO. 3
RADIATOR FAN NO. 1 - SHORTED
RADIATOR FAN NO. 2 - SHORTED
RADIATOR FAN RELAY NO. 1 OUTPUT CIRCUIT SHORTED TO GROUND
RADIATOR FAN RELAY NO. 2 AND NO. 3 COMMON OUTPUT CIRCUIT OPEN FROM RELAY NO.
2
RADIATOR FAN RELAY NO. 3 GROUND CIRCUIT OPEN
HIGH SPEED RADIATOR FAN DUAL RELAY CONTROL CIRCUIT OPEN
RADIATOR FAN RELAY NO. 1 OUTPUT CIRCUIT OPEN
RADIATOR FAN NO. 1 CONTROL CIRCUIT OPEN
RADIATOR FAN RELAY NO. 2 AND NO. 3 COMMON OUTPUT CIRCUIT OPEN FROM RELAY NO.
3
RADIATOR FAN - OPEN
RADIATOR FAN NO. 2 - OPEN
186
DRIVEABILITY - DIESEL
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRBIIIt, read DTCs.
Are any Radiator Fan DTCs present?All
Ye s®Refer to symptom list for problems related to Radiator Fan
control.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 2
2NOTE: The engine temperature must not be hot enough to cause the
radiator fans to be on with the key off.
Turn the ignition off.
Observe the radiator fans with the key off.
Is either radiator fan running with the key off?All
Ye s®Go To 3
No®Go To 6
3NOTE: The engine temperature must not be hot enough to cause the
radiator fans to be on with the key off.
Turn the ignition off.
Observe the radiator fans with the key off.
Which radiator fan(s) are running?All
Fan 1 and Fan 2
Go To 4
Fan 2 Only
Go To 5
4NOTE: The engine temperature must not be hot enough to cause the
radiator fans to be on with the key off.
Turn the ignition off.
Remove Radiator Fan Relay No. 1.
Observe the radiator fans.
Did the radiator fans stop running?All
Ye s®Replace Radiator Fan Relay No. 1.
Perform ROAD TEST VERIFICATION - VER-2.
No®Repair the Radiator Fan Relay No. 1 Output circuit for a short to
voltage.
Perform ROAD TEST VERIFICATION - VER-2.
5NOTE: The engine temperature must not be hot enough to cause the
radiator fans to be on with the key off.
Turn the ignition off.
One at a time, remove Radiator Fan Relay No. 2 and then Radiator Fan Relay No. 3.
Observe the radiator fans after disconnecting each relay.
Did the radiator fan stop running?All
Ye s®Replace Radiator Fan Relay that caused the radiator fan to stop.
Perform ROAD TEST VERIFICATION - VER-2.
No®Repair the Radiator Fan Relay No. 2 and No. 3 Common Output
circuit for a short to voltage.
Perform ROAD TEST VERIFICATION - VER-2.
187
DRIVEABILITY - DIESEL
*CHECKING THE ELECTRIC RADIATOR FAN OPERATION ÐContinued
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
TEST ACTION APPLICABILITY
15 Turn the ignition off.
Disconnect the Radiator Fan Relay No. 1 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 16
No®Repair the Radiator Fan Relay No. 1 Fused B+ circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
16 Turn the ignition off.
Install a substitute relay in place of Radiator Fan Relay No. 1.
Turn the ignition on.
With the DRB, actuate the Low Speed Fan Relay.
Do both Radiator Fans cycle on and off?All
Ye s®Replace Radiator Fan Relay No. 1.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 17
17 Turn the ignition off.
Disconnect the Radiator Fan Relay No. 1 harness connector.
Disconnect the Radiator Fan No. 1 harness connector.
Using a 12-volt test light connected to 12-volts, check the Radiator Fan Relay No. 1
Output circuit in the Radiator Fan Relay No. 1 harness connector.
Did the test light illuminate?All
Ye s®Repair the Radiator Fan Relay No. 1 Output circuit for a short to
ground.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 18
18 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 19
No®Repair the Radiator Fan Relay No. 3 Ground circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
19 Turn the ignition off.
Disconnect the Radiator Fan Relay No. 1 harness connector.
Disconnect the Radiator Fan No. 1 harness connector.
Measure the resistance of the Radiator Fan Relay No. 1 Output circuit.
Is the resistance below 5.0 ohms?All
Ye s®Go To 20
No®Repair the Radiator Fan Relay No. 1 Output circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
190
DRIVEABILITY - DIESEL
*CHECKING THE ELECTRIC RADIATOR FAN OPERATION ÐContinued
TEST ACTION APPLICABILITY
20 Turn the ignition off.
Disconnect the Radiator Fan Relay No. 3 harness connector.
Disconnect the Radiator Fan No. 1 harness connector.
Measure the resistance of the Radiator Fan No. 1 Control circuit.
Is the resistance below 5.0 ohms?All
Ye s®Go To 21
No®Repair the Radiator Fan No. 1 Control circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
21 Turn the ignition off.
Disconnect the Radiator Fan Relay No. 3 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. 3.
Is the resistance below 5.0 ohms?All
Ye s®Go To 22
No®Repair the Radiator Fan Relay No. 2 and No. 3 Common Output
circuit from Radiator Fan Relay No. 3 for an open.
Perform ROAD TEST VERIFICATION - VER-2.
22 Turn the ignition off.
Disconnect the Radiator Fan No. 1 harness connector.
Connect a fused jumper wire between the Radiator Fan No. 1 harness connector
cavities.
Turn the ignition on.
With the DRB, actuate the Low Speed Fan Relay.
Did Radiator Fan No. 2 activate on High speed?All
Ye s®Replace Radiator Fan No. 1.
Perform ROAD TEST VERIFICATION - VER-2.
No®Replace Radiator Fan No. 2.
Perform ROAD TEST VERIFICATION - VER-2.
23NOTE: Radiator Fan No. 2 is fed voltage from Radiator Fan Relay No. 3
during low speed operation and then fed voltage from Radiator Fan Relay
No. 2 during high speed operation by a common circuit connected to both
relays.
Turn the ignition off.
Disconnect the Radiator Fan Relay No. 2 harness connector.
Disconnect the Radiator Fan Relay No. 3 harness connector.
Disconnect the Radiator Fan No. 2 harness connector.
Measure the resistance between ground and the Radiator Fan Relay No. 2 and No. 3
Common Output circuit.
Is the resistance above 100k ohms?All
Ye s®Go To 24
No®Repair the Radiator Fan Relay No. 2 and No. 3 Common Output
circuit for a short to ground.
Perform ROAD TEST VERIFICATION - VER-2.
191
DRIVEABILITY - DIESEL
*CHECKING THE ELECTRIC RADIATOR FAN OPERATION ÐContinued
TEST ACTION APPLICABILITY
24 Turn the ignition off.
Disconnect the Radiator Fan Relay No. 3 harness connector.
Disconnect the Radiator Fan No. 1 harness connector.
Using a 12-volt test light connected to 12-volts, check the Radiator Fan No. 1 Control
circuit.
Did the test light illuminate?All
Ye s®Repair the Radiator Fan No. 1 Control circuit for a short to
ground.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 25
25 If there are no possible causes remaining, view repair. All
Repair
Replace the Radiator Fan No. 2.
Perform ROAD TEST VERIFICATION - VER-2.
26 Turn the ignition off.
Disconnect the Radiator Fan Relay No. 3 harness connector.
Disconnect the Radiator Fan No. 1 harness connector.
Measure the voltage on the Radiator Fan No. 1 Control circuit.
Is the voltage above 1.0 volt?All
Ye s®Repair the Radiator Fan No. 1 Control circuit for a short to
voltage.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 27
27 If there are no possible causes remaining, view repair. All
Repair
Replace Radiator Fan No. 1.
Perform ROAD TEST VERIFICATION - VER-2.
192
DRIVEABILITY - DIESEL
*CHECKING THE ELECTRIC RADIATOR FAN OPERATION ÐContinued
Symptom:
*CHECKING THE GLOW PLUG OPERATION
POSSIBLE CAUSES
CHECKING THE GLOW PLUGS
FUSED B+ CIRCUIT OPEN
GLOW PLUG RELAY OUTPUT CIRCUIT SHORTED TO VOLTAGE
GLOW PLUG RELAY OUTPUT CIRCUIT SHORTED TO GROUND
GLOW PLUG RELAY OUTPUT CIRCUIT OPEN
GLOW PLUG RELAY
TEST ACTION APPLICABILITY
1 Turn the ignition off.
Disconnect the Glow Plug harness connectors for all cylinders.
Turn the ignition on.
With the DRB, actuate the Glow Plug Relay.
Using a 12-volt test light connected to ground, probe each Glow Plug harness
connector during actuator test.
Does the test light cycle on and off for each circuit during the actuator test?All
Ye s®Go To 2
No®Go To 3
2 Refer to the Service Information and perform the Glow Plug Test.
Are all Glow Plugs operating properly?All
Ye s®Test Complete.
No®Replace the Glow Plug(s) as necessary.
Perform ROAD TEST VERIFICATION - VER-2.
3NOTE: If the Glow Plug Relay fuse or fuselink is open, refer to the system
schematics for all circuits that are powered by the Glow Plug Relay fuse or
fuselink to determine the cause of the blown fuse/fuselink.
Remove the Glow Plug Relay.
Using a 12-volt test light connected to ground, probe the Fused B+ circuit in the Glow
Plug Relay connector, cavity 30 in the IPM.
Does the test light illuminate brightly?All
Ye s®Go To 4
No®Repair the Fused B+ (Fuse/Fuselink) circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
4 Turn the ignition off.
Disconnect all the Glow Plug harness connectors.
Remove the Glow Plug Relay.
Turn the ignition on.
Measure the voltage on the Glow Plug Relay Output circuit.
Is the voltage above 1.0 volt?All
Ye s®Repair the Glow Plug Relay Output circuit for a short to voltage.
Perform ROAD TEST VERIFICATION - VER-2.
No®Go To 5
195
DRIVEABILITY - DIESEL