P1491: Cooling Fan Relay Control Circuit: Testing

Ignition on, engine not running. With the DRBIII®, read DTCs and record the related Freeze Frame data. With the DRBIII®, actuate the Cooling Fan Relay. Is the Cooling Fan operating? If yes, refer to the INTERMITTENT CONDITION under SELF-DIAGNOSTIC SYSTEM. If no, go to the next step.
Turn the ignition off. Remove the Cooling Fan Relay. Using a 12-volt test light connected to ground, probe the Fused B+ circuit of the Cooling Fan Relay connector. Is the voltage above 11.0 volts? If yes, go to the next step. If no, repair the open or short to ground in the Fused B+ circuit. Check and replace any open fuses.
Using a 12-volt test light connected to 12-volts, probe the ground circuit in the Cooling Fan Relay harness connector. Does the test light illuminate brightly? If yes, go to the next step. If no, repair the open in the ground circuit.
Disconnect the PCM harness connectors. Measure the resistance of the (K173) Cooling Fan Relay Control circuit between the Cooling Fan Relay connector and the PCM harness connector. Is the resistance below 5.0 ohms? If yes, repair the open in the (K173) Cooling Fan Relay Control circuit. If no, go to the next step.
Measure the resistance between ground and the (K173) Cooling Fan Relay Control circuit at Relay connector. Is the resistance below 100 ohms? If yes, go to next step. If no, repair the short to ground in the (K173) Cooling Fan Relay control circuit.

NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

Using the wiring diagram as a guide, inspect the wire harness and connectors. Pay particular attention to all power and ground circuits. If there are no possible causes remaining, replace PCM. Program the new PCM. See PROGRAMMING .