When Monitored and Set Condition:
P1491-RAD FAN CONTROL RELAY CIRCUIT
When Monitored: With the ignition key on, battery voltage greater than 10.0 volts and
the PCM requests the radiator fan to be turned on.
Set Condition: An open or shorted circuit is detected in the radiator fan relay control
RADIATOR FAN CTRL RLY CIRCUIT WIRE HARN INTERMITTENT DEFECT
RADIATOR FAN CTRL RLY CIRCUIT WIRE HARN OBSERVABLE DEFECT
RADIATOR FAN RELAY GROUND CIRCUIT OPEN
RAD FAN RELAY CONTROL CIRCUIT OPEN
RADIATOR FAN RELAY CONTROL CIRCUIT SHORT TO GROUND
RAD FAN CONTROL RELAY DEFECTIVE
Ignition On, Engine Not Running
With the Scan tool, actuate the Radiator Fan Control.
Does the Radiator Fan Motor Cycle on and off?
Yes Go To 641
No Go To 643
With the DRB, actuate the Radiator Fan Control.
Wiggle the Wiring Harness from the Relay to the Powertrain Control Module.
Did the wiggling interrupt the Radiator Fan Motor cycling?
Yes Repair as necessary where wiggling caused the cycling to be
No Go To 642
Turn ignition off.
inspect the Wiring and Connectors.
Were any problems found?
Yes Repair as necessary.
No Test Complete.
Disconnect the Radiator Fan Relay.
Using an ohmmeter, measure the Radiator Fan Relay Ground Circuit to Ground.
Is the resistance below 5.0 ohms?
Yes Go To 644
No Repair the open Ground Circuit.
Disconnect the PCM Connector.
Note: Check connectors - Clean/repair as necessary.
Disconnect the Radiator Fan Relay Connector.
Using an Ohmmeter, measure the resistance of the Rad Fan Relay Control Circuit
from the Relay to the PCM.
Yes Go To 645
No Repair the open Radiator Fan Relay Control Circuit.
Using an Ohmmeter, measure the Radiator Fan Relay Control Circuit to ground.
Yes Repair the Radiator Fan Relay Control Circuit for a short to
No Go To 646
Connect a jumper wire to the Radiator Fan Relay Control Circuit at PCM.
Momentarily connect the other end of the jumper wire to a good ground.
Did the Radiator Fan actuate?
Yes Replace the Radiator Fan Relay.
No Go To 647
If there are no other potential causes remaining, the PCM is assumed to be defective.
View repair options.
Replace the PCM.
I hope that this helps you