Diagnostic Aids

PCM determines engine cooling fan requirements and controls fan operation through Fan Control (FC) circuits. Continuous memory DTCs indicates an FC circuit failure occurred during vehicle operation. Possible causes are:

Open VPWR circuit to FC relay.
Open or shorted FC circuit.

Introduction

Turn ignition off. Ensure A/C and defogger are off. Install scan tool. Disconnect cooling fan motor harness connector(s). Check for corroded, damaged or backed-out terminals. Repair as necessary. Connect a test light between power-to-fan circuit and ground circuit at fan motor harness connector. Turn ignition on with engine off. Using scan tool, access OUTPUT TEST MODE. Command low speed fan on. Test light should be on. Observe test light for indication of fault (test light will turn off to indicate fault) while performing the following:
- Shake and bend FC circuit between PCM and FC relay.
- Shake and bend VPWR circuit to FC relay.
- Lightly tap on FC relay to simulate road shock.
If fault is indicated, turn ignition off. Isolate and repair open or short to power in wiring harness. Repeat QUICK TEST. See TESTS W/CODES - INTRODUCTION article. If fault is not indicated, go to next step.

Check FC Circuit For Short To Ground

Turn ignition on, engine off. Ensure cooling fan motor harness connector(s) are disconnected and test light is still installed. Using scan tool, command low speed fan off. Test light should be off. Observe test light for indication of fault (test light will turn on to indicate fault) while performing the following:
- Shake and bend FC circuit between PCM and FC relay.
- Lightly tap on FC relay to simulate road shock.
If fault is indicated, isolate and repair short to ground in wiring harness. Repeat QUICK TEST. See TESTS W/CODES - INTRODUCTION article. If fault is not indicated, problem may be intermittent. Ensure all applicable connections are clean and tight, and go to DIAGNOSTIC TEST Z (INTERMITTENT) .