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 | ..... | Blue |
| Cooling Fan PWR | ..... | Blue |
- Check Fan Operation
Turn ignition off. Connect NGS scan tool to fuse panel DLC. Turn ignition on. 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 (Blue wire) at relay connector in question. See Fig 1. If voltage is greater than 10 volts, go to next step. If voltage is less than 10 volts, repair open PWR circuit (Blue wire). See CIRCUIT PIN IDENTIFICATION table. Restore all electrical connections and repeat QUICK TEST . - Check Signal Circuit For Open
Disconnect PCM. 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. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open in SIG circuit. Restore all electrical connections and repeat QUICK TEST . - Check Signal Circuit For Short
Disconnect PCM. Disconnect applicable fan relay. Measure resistance of applicable SIG circuit between PCM connector and ground. See CIRCUIT PIN IDENTIFICATION table. If resistance is greater than 10 k/ohms, go to next step. If resistance is less than 10 k/ohms, repair short to ground in SIG circuit. Restore all electrical connections and repeat QUICK TEST . - Check Fan Operation
Disconnect PCM. Turn ignition on. Ground SIG circuit of applicable relay. See CIRCUIT PIN IDENTIFICATION table. Relay should click and fan should operate when grounded. If relay does not click, replace relay. Restore all electrical connections and repeat QUICK TEST . If relay clicks and fan operates, replace PCM. Restore all electrical connections and repeat QUICK TEST.