DTC P1490: Low Speed Fan Control Relay Circuit: Testing
- Turn ignition on. Using scan tool, actuate low speed radiator fan relay. Locate low speed radiator fan relay in Power Distribution Center (PDC). See Fig 1 . If low speed radiator fan relay cycles on and off, go to next step. If low speed radiator fan relay does not cycle on and off, stop relay actuation and go to step 4 .
- Ensure low speed radiator fan relay is still actuated. Wiggle wiring harness from low speed radiator fan relay to PCM. PCM is located on left side of engine compartment, between PDC and Transmission Control Module (TCM). See Figure . If low speed radiator fan relay actuation is interrupted, repair connector or wiring harness where wiggling caused interruption. If no problems were found, go to next step.
- Conditions that set DTC are not present at this time. Perform the following to help identify intermittent condition:
- With engine running at normal operating temperature, wiggle related wiring harness while monitoring related parameters on scan tool. If voltage changes or DTC sets while wiggling wiring harness, repair connectors or wiring harness where wiggling caused voltage to change or DTC to set.
- Review freeze frame information on scan tool. Duplicate conditions present when DTC was set.
- Refer to any technical service bulletins that may apply.
- Visually inspect related wiring harness. Check for chafed, pierced, pinched or partially broken wires.
- Visually inspect related wiring harness connectors. Check for broken, bent, pushed out or corroded terminals.
If a problem is found, repair as necessary. If no problems are found, test is complete.
- Turn ignition off. Remove low speed radiator fan relay from PDC. Turn ignition on. Measure voltage between ground and fused ignition switch output circuit (Light Green/Black wire) at terminal "A" at low speed radiator fan relay harness connector. See Fig 1 . If voltage is more than 11 volts, go to next step. If voltage is 11 volts or less, repair open or short in fused ignition switch output circuit. See WIRING DIAGRAMS article.
- Measure resistance between low speed radiator fan relay terminals "A" and "C". If resistance is 60-80 ohms, go to next step. If resistance is not 60-80 ohms, replace low speed radiator fan relay.
- Turn ignition off. Disconnect PCM harness connectors. See Figure . Measure resistance of low speed radiator fan relay control circuit (Dark Blue/Pink wire) between terminal "C" at low speed radiator fan relay harness connector and terminal No. 55 at PCM C2 harness connector. See Figure . If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in Dark Blue/Pink wire.
- Measure resistance between ground and low speed radiator fan relay control circuit (Dark Blue/Pink wire) at terminal "C" at low speed radiator fan relay harness connector. If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair short to ground in Dark Blue/Pink wire.
- If no other possible causes are remaining, PCM is assumed to be defective. Replace PCM.