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DTC P1491: Rad Fan Control Relay Circuit: Testing

  1. Turn ignition on. Using scan tool, actuate radiator fan relay. Check radiator fan operation. If radiator fan cycles on and off, go to next step. If radiator fan does not cycle on and off, go to step  4.
  2. Ensure ignition is still on and radiator fan control relay is still actuated. Wiggle wiring harness and connectors between radiator fan relay and PCM while noting operation of radiator fans. Radiator fan relay is located on the front bumper reinforcement, in front of the A/C condenser. PCM is located between on left side of engine compartment, in front of battery. If radiator fan operation was not interrupted while wiggling wiring harness and connectors, go to next step. If radiator fan operation was interrupted while wiggling wiring harness and connectors, repair wiring harness as necessary where wiggling caused radiator fan operation to be interrupted.
  3. At this time, conditions for DTC to set do not exist or fault is an intermittent problem. Start engine and allow it to idle. Ensure engine is at normal operating temperature. Using scan tool, monitor parameters related to DTC while wiggling connectors and wiring harness. If value changes while wiggling connectors and wiring harness, repair connectors and wiring harness where wiggling caused value to change. If value does not change, review Freeze Frame data using scan tool. Attempt to duplicate condition that caused DTC to set. Check for any related technical service bulletins that may apply. Visually inspect related connectors and wiring harness. Repair connectors and wiring harness as necessary. See WIRING DIAGRAMS article. If no problems are indicated, test is complete.
  4. Turn ignition off. Disconnect radiator fan relay connector. Radiator fan relay is located on the front bumper reinforcement, in front of the A/C condenser. Using a test light connected to positive battery voltage, probe Black/Dark Green wire at radiator fan relay harness connector. If test light illuminates, go to next step. If test light does not illuminate, repair open in ground circuit (Black/Dark Green wire) to radiator fan relay.
  5. Measure voltage between ground and Orange/Red wire at radiator fan relay harness connector. If voltage is more than 11 volts, go to next step. If voltage is 11 volts or less, repair open in power circuit (Orange/Red wire) between radiator fan relay and Integrated Power Module (IPM). IPM is located on left side of engine compartment, next to battery. Also check fuse No. 27 (40-amp) in IPM. Repair wiring or replace fuse as necessary.
    NOTE: The Intelligent Power Module (IPM) may also be referred to as Integrated Power Module (IPM) or Power Distribution Center (PDC).
  6. Ensure ignition is off. Disconnect PCM connectors. PCM is located on left side of engine compartment, in front of battery. Reconnect radiator fan relay connector. Connect one end of a jumper wire to terminal No. 73 (Brown/Violet wire) at PCM C2 harness connector. Briefly tap other end of jumper wire to ground and observe radiator fan operation. If radiator fan turns on, replace PCM. Program the new PCM. See PROGRAMMING . If radiator fan does not turn on, go to next step.
  7. Measure resistance between Dark Blue/Violet wire at radiator fan relay harness connector and terminal No. 73 (Brown/Violet wire) at PCM C2 harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, go to step  11.
  8. Measure resistance between ground and Dark Blue/Violet wire at radiator fan relay harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, replace radiator fan relay.
  9. Disconnect IPM C2 connector. Measure resistance between ground and Dark Blue/Violet wire at 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/Violet wire between radiator fan relay and IPM.
  10. Ensure ignition is off and PCM is still disconnected. Disconnect IPM C3 connector. Measure resistance between ground and terminal No. 73 (Brown/Violet wire) at PCM C2 harness connector. If resistance is 5 ohms or more, replace IPM. If resistance is less than 5 ohms, repair short to ground in Brown/Violet wire between IPM and PCM.
  11. Disconnect IPM C2 connector. Measure resistance of Dark Blue/Violet wire between radiator fan relay harness connector and terminal No. 1 at IPM C2 harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in Dark Blue/Violet wire.
  12. Ensure ignition is off and PCM is still disconnected. Disconnect IPM C3 connector. Measure resistance of Brown/Violet wire between terminals No. 18 at IPM C3 harness connector and No. 73 at PCM C2 harness connector. If resistance is less than 5 ohms, replace IPM. If resistance is not less than 5 ohms, repair open in Brown/Violet wire between IPM and PCM.
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