LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Dodge and Ram >> 2001 >> Neon Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P1490: Low Speed Fan Control Relay Circuit >> Testing
April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC P1490: Low Speed Fan Control Relay Circuit: Testing

  1. Turn ignition on. Using scan tool, actuate radiator fan relay. Locate radiator fan relay in Power Distribution Center (PDC). See Figure . If radiator fan relay cycles on and off, go to next step. If radiator fan relay does not cycle on and off, stop relay actuation and go to step  4 .
  2. Ensure radiator fan relay is still actuated. Wiggle wiring harness from radiator fan relay PCM. PCM is located in engine compartment, between air cleaner and radiator. If radiator fan relay actuation is interrupted, repair connector or wiring harness where wiggling caused interruption. If no problems were found, go to next step.
  3. 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 (TSBs) 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.

  4. Turn ignition off. Remove radiator fan relay from PDC. Turn ignition on. Measure voltage between ground and fused ignition switch output circuit (Dark Blue/White wire) at terminal No. 69 at radiator fan relay harness connector. See Figure . 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.
  5. Measure resistance between radiator fan relay terminals No. 69 and 70. See Figure . If resistance is 60-80 ohms, go to next step. If resistance is not 60-80 ohms, replace radiator fan relay.
  6. Turn ignition off. Disconnect PCM harness connectors. PCM is located in engine compartment, between air cleaner and radiator. Measure resistance of control circuit (Dark Blue/Pink wire) between terminal No. 70 at 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.
  7. Measure resistance between ground and control circuit (Dark Blue/Pink wire) at terminal No. 70 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/Pink wire.
  8. If no other possible causes are remaining, replace PCM.
scientia non olet · About LEMON Manuals