TEST
ACTION
APPLICABILITY
2
WARNING: 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
Yes
→ Repair as necessary.
Perform ROAD TEST VERIFICATION - VER-2.
No
→ Test Complete.
3
Turn the ignition off.
Disconnect the Radiator Fan Relay No. 1 harness connector.
Turn the ignition on.
Using a 12-volt test light connected to ground, check the ECM/PCM Relay Output
circuit.
Did the test light illuminate brightly?
All
Yes
→ Go To 4
No
→ Repair the ECM/PCM Relay Output circuit for an open.
Perform ROAD TEST VERIFICATION - VER-2.
4
Turn the ignition off.
Install a substitute relay in place of the Radiator Fan Relay No. 1.
Turn the ignition on.
With the DRB, actuate the Low Speed Fan Relay.
Do the Radiator Fans cycle on and off?
All
Yes
→ Replace Radiator Fan Relay No. 1.
Perform ROAD TEST VERIFICATION - VER-2.
No
→ Go To 5
5
Turn the ignition off.
Disconnect the Radiator Fan Relay No. 1 harness connector.
Disconnect the ECM harness connectors.
Measure the resistance between ground and the Low Speed Radiator Fan Control
circuit.
Is the resistance below 100 kohms?
All
Yes
→ Repair the Low Speed Radiator Fan Control circuit for a short to
ground.
Perform ROAD TEST VERIFICATION - VER-2.
No
→ Go To 6
83
DRIVEABILITY - DIESEL
P0480-FAN 1 CONTROL CIRCUIT OPEN CIRCUIT —
Continued