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DTC 1900: Radiator Cooling Fan Control

  1. Cooling Fan Motor No. 1 Operation  - Turn ignition off. Disconnect radiator cooling fan relay No. 2. See Figure. Disconnect Engine Coolant Temperature (ECT) sensor connector. Connect a 150-ohm resistor between ECT terminals. Start engine and allow to idle for several minutes. If cooling fan No. 1 does not operate, go to step 3). If cooling fan No. 1 operates, turn ignition off and go to next step.
  2. Cooling Fan Motor No. 2 Operation  - Turn ignition off. Reconnect cooling fan relay No. 2. Disconnect cooling fan relay No. 1. See Figure. Start engine and allow to idle for several minutes. If cooling fan No. 2 does not operate, go to step 10). If cooling fan No. 1 operates, check for fault in cooling system. If no faults are found, replace triple switch. If fault is still present, go to next step.
  3. Check Power Supply  - Turn ignition off. Disconnect cooling fan relay No. 1. See Figure. Turn ignition on. Measure voltage between ground and relay No. 1, terminals No. 1 and 3. See Fig 1. If battery voltage is present, go to step 5). If battery voltage is not present, go to next step.
  4. Check 10-amp fuse, 30-amp fusible link and harness connectors. Ensure continuity exists between fan relay No. 1 and battery. Repair or replace harness and/or connector as necessary.
  5. Check Ground Circuit  - Turn ignition off. Loosen and retighten engine ground bolts. See Figure. Disconnect cooling fan motor harness connector. See Figure. Check for continuity as follows:
    • Between relay No. 1 terminal No. 5 and cooling fan motor connector terminals No. 1 and 2. See Fig 2.
    • Between engine ground and cooling fan motor connector terminals No. 3 and 4. See Fig 3.

    If continuity is present, go to next step. If continuity is not present, repair harness or connectors as necessary and retest.

  6. Check Output Signal Circuit  - Leave ignition off. Disconnect ECM harness connector. Check for continuity between cooling fan relay No. 1, terminal No. 2, and ECM harness connector terminal No. 34. If continuity is not present, repair harness or connector. If continuity is present, go to next step.
  7. Check Ground Circuit  - Turn ignition off. Disconnect triple switch and cooling fan relay No. 1 harness connector. Check for continuity as follows:
    • Between relay No. 1 terminal No. 2 (Light Green/Red wire) and triple switch connector terminal No. 2. (Light Green/Red wire)
    • Between engine ground and triple switch connector terminal No. 3 (Black wire).

    If continuity is present, go to next step. If continuity is not present, repair harness or connectors as necessary and retest.

  8. Check Cooling Fan Motor  - With cooling fan motor disconnected, apply fused battery power to terminal No. 1. Connect terminal No. 3 to ground. See Fig 4. Cooling fan motor should operate. Apply fused battery power to terminal No. 2. Connect terminal No. 4 to ground. Cooling fan motor should operate. Replace cooling fan motor if operation is not as specified. If motor operates as specified, go to next step.
  9. Check Cooling Fan Relay  - Connect relay terminal No. 1 to ground. See Fig 5. Using jumper wire, apply battery voltage to terminal No. 2. Check continuity between relay terminals No. 3 and 5. Continuity should be present. Remove battery voltage from relay. Again, check continuity between relay terminals No. 3 and 5. Continuity should not be present. If continuity is not as specified, replace cooling fan relay. If continuity is as specified, check connector pins for damage or corrosion. Check all circuit connectors for clean, tight fit. Service if necessary and retest.
  10. Check Power Supply  - Turn ignition off. Disconnect cooling fan relay No. 2 harness connector. Turn ignition on. Measure voltage as follows:
    • Between ground and relay No. 2, terminals No. 1 (Brown wire terminal).
    • Between ground and relay No. 2, terminals No. 3 (White/Blue wire terminal).

    If battery voltage is present, go to next step. If battery voltage is not present, check 10-amp fuse, 30-amp fusible link and harness connectors. Ensure continuity exists between fan relay No. 2 and battery. Repair or replace harness and/or connector as necessary.

  11. Check Ground Circuit  - Turn ignition off. Disconnect cooling fan motor No. 2 harness connector. Check continuity as follows:
    • Between cooling fan motor No. 2, connector terminal No. 1 (White/Black wire) and cooling fan relay No. 2, terminal No. 5.
    • Between cooling fan motor No. 2, connector terminal No. 2 (White/Black wire) and cooling fan relay No. 2, terminal No. 5.
    • Between ground and cooling fan motor No. 2, connector terminal No.3.
    • Between ground and cooling fan motor No. 2, connector terminal No. 4.

    If continuity is present, go to next step. If continuity is not present, repair harness or connectors as necessary.

  12. Check Output Signal Circuit  - Leave ignition off and cooling fan relay harness connector disconnected. Disconnect ECM harness connector. Check for continuity between cooling fan relay No. 2, terminal No. 2 (Light Green wire) and ECM connector terminal No. 33. If continuity is present, go to step 8). If continuity is not present, repair harness or connectors as necessary.
Fig 1: Locating Cooling Fan Relays
G97D06701Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 2: Locating Cooling Fan Motor Harness Connectors
G97F06702Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 3: Checking Power Supply Circuit
G97H06703Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 4: Checking Ground Circuit
G97J06704Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 5: Checking Ground Circuit
G97C06705Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 6: Checking Cooling Fan Motor
G96D10770Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 7: Identifying Cooling Relay Terminals
G96E10771Courtesy of NISSAN MOTOR CO., U.S.A.
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