Diagnostic Aids
Perform this test when instructed during QUICK TEST or other test step. This test is only intended to diagnose the following:
- Cooling fan harness circuits.
- High fan control relays.
- Low fan control relay.
- PCM.
CIRCUIT PIN IDENTIFICATION
| Circuit | PCM Pin No. | Wire Color |
|---|---|---|
| HFAN SIG | 32 | Brown/White |
| LFAN SIG | 34 | Blue/Orange |
| Relay PWR | N/A | Blue |
| Cooling Fan PWR | N/A | Blue |
- Check Fan Operation
Turn ignition off. Connect New Generation Star (NGS) tester to DLC. Turn ignition on. Using NGS tester, enter active command mode. Access PID for applicable circuit. Attempt to activate applicable fan. If fan does not operate normally, go to next step. If fan operates normally, fault may be intermittent, go to TEST Z . - Check Power To Relay
Turn ignition off. Disconnect harness connector of relay in question. Turn ignition on. Measure voltage of PWR circuit at relay connector in question. See Fig 1. If voltage is greater than 10 volts, go to next step. If voltage is not greater than 10 volts, repair open in circuit. See WIRING DIAGRAMS article. Reconnect all electrical connections and repeat QUICK TEST . - Check Signal Circuit For Open
Turn ignition off. Disconnect PCM harness connector. Measure resistance of SIG circuit of applicable relay between PCM harness connector and SIG circuit at harness connector of applicable relay. CIRCUIT PIN IDENTIFICATION table. See Figure and Fig 1 . If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open in circuit. - Check Signal Circuit For Short
Measure resistance of applicable SIG circuit between PCM connector and ground. See CIRCUIT PIN IDENTIFICATION table. See Figure. If resistance is greater than 10 k/ohms, go to next step. If resistance is not greater than 10 k/ohms, repair short in circuit. - Check Fan Operation
Install relay. Turn ignition on. Ground SIG circuit of applicable relay at PCM harness connector. See CIRCUIT PIN IDENTIFICATION table. Relay should click and fan should operate when grounded. If relay does not click, replace relay. If relay clicks and fan operates, replace PCM.