Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Test KF: Fan Control Relays: Testing
- 1) Check Relay Function
This test addresses cooling fan operation concerns. Possible causes are as follows:- Open or shorted signal circuits.
- Open PWR circuits.
- Damaged relays.
- Damaged PCM.
Turn ignition off. Connect scan tool to DLC. Turn ignition on. Using scan tool, access ACTIVE COMMAND MODES. Select FANSP PID for low speed fan control circuit or FANHP PID for high speed fan control circuit. Using scan tool, command applicable fan ON. If fan does not operate normally, go to next step. If fan operates normally, fault may be intermittent. Go to TEST Z , step 1), or go to INTERMITTENTS in TROUBLE SHOOTING - NO CODES - VILLAGER article.
- 2) Check PWR Circuit To Relay
Turn ignition off. Remove suspect relay from battery junction box. See Figure. Turn ignition on. Using DVOM, measure voltage between chassis ground and PWR circuit to suspect relay cavity No. 1. See Figure. If voltage is more than 10 volts, go to next step. If voltage is 10 volts or less, repair open in affected PWR circuit. See wiring diagram in ELECTRIC COOLING FANS - VILLAGER article in ENGINE COOLING. - 3) Check SIG Circuit To PCM For Open
Turn ignition off. Disconnect PCM harness connector. Inspect connector for damaged pins and repair if necessary. Using DVOM, measure resistance of SIG circuit between suspect relay cavity No. 2 and PCM harness connector terminal. See FAN CONTROL RELAY SIG CIRCUIT, PID & TERMINAL IDENTIFICATION table. See Figure and Figure . If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in appropriate SIG circuit. - 4) Check SIG Circuit To PCM For Short
Using DVOM, measure resistance between chassis ground and suspect SIG circuit at PCM harness connector terminal. See FAN CONTROL RELAY SIG CIRCUIT, PID & TERMINAL IDENTIFICATION table. See Figure. If resistance is more than 10 k/ohms, leave PCM disconnected and go to next step. If resistance is 10 k/ohms or less, repair short to ground in appropriate SIG circuit. See wiring diagram in ELECTRIC COOLING FANS - VILLAGER article in ENGINE COOLING. - 5) Check Fan Operation
Install cooling fan relay in battery junction box. Turn ignition on. Connect a jumper wire between chassis ground and suspect SIG circuit at PCM harness connector terminal. See FAN CONTROL RELAY SIG CIRCUIT, PID & TERMINAL IDENTIFICATION table. See Figure. Relay should click and fan should operate when SIG circuit is grounded. If relay does not click and fan does not operate, replace faulty relay. If relay clicks and fan operates, replace PCM.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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