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Home >> Jeep >> 2001 >> Cherokee Classic, 4WD, Part Time >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P1491: Radiator Fan Control Relay Circuit >> Testing
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DTC P1491: Radiator Fan Control Relay Circuit: Testing

  1. Turn ignition on. Using scan tool, read DTCs. If GOOD TRIP counter is displayed for DTC P1486 and displayed count is "0", go to next step. If GOOD TRIP counter is not displayed for DTC P1486 or displayed count is not "0", go to step  7 .
  2. Turn ignition on. Using scan tool, actuate radiator fan relay. Locate radiator fan relay in Power Distribution Center (PDC). PDC is located in engine compartment, next to battery. See Figure . Listen for radiator fan relay operation. If radiator fan relay clicks, go to next step. If radiator fan relay does not click, stop radiator fan relay actuation and go to step  5 .
  3. Ensure ignition is still on and radiator fan control relay is still actuated. Wiggle wiring harness and connectors from radiator fan control relay to PCM while noting operation of radiator fans. PCM is located in engine compartment on left front fender, near radiator support. If radiator fan relay clicking was not interrupted while wiggling wiring harness and connectors, go to next step. If radiator fan relay clicking was interrupted while wiggling wiring harness and connectors, repair wiring harness as necessary where wiggling caused radiator fan relay to stop clicking.
  4. Turn ignition off. Inspect wiring and connectors between radiator fan relay and PCM. If no problems exist, test is complete. If any problems exist, repair wiring or connectors as necessary.
  5. Turn ignition off. Remove radiator fan relay from PDC. Turn ignition on. Using voltmeter, measure voltage between ground and terminal D11 (White wire) at radiator fan relay socket in PDC. See Figure . If voltage is more than 10 volts, go to next step. If voltage is 10 volts or less, check for open in White wire between radiator fan relay and junction block. Junction block is located behind passenger-side kick panel. Also check fuse No. 10 (15-amp) in junction block. See WIRING DIAGRAMS article. Repair wiring or replace fuse as necessary.
  6. Turn ignition off. Using ohmmeter, measure resistance between terminals No. 85 and 86 at radiator fan relay. See Figure . If resistance is 50-90 ohms, go to next step. If resistance is not 50-90 ohms, replace radiator fan relay.
  7. Ensure ignition is off. Disconnect PCM connectors. PCM is located in engine compartment on left front fender, near radiator support. Inspect connectors for damaged pins, corrosion and loose terminals. Repair connectors as necessary. If connectors are okay, measure resistance between ground and terminal No. 2 (Dark Blue/Pink wire) at PCM C3 harness connector. See Figure . 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.
  8. Measure resistance of Dark Blue/Pink wire between terminal No. D13 at radiator fan relay socket in PDC and terminal No. 2 at PCM C3 harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open Dark Blue/Pink wire between radiator fan relay and PCM.
  9. At this time, PCM is assumed to be defective. Replace PCM.
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