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DTC P1900 - Radiator Cooling Fan Control

  1. Check Cooling Fan Operation

    Turn ignition off. Disconnect triple-pressure switch harness connector. See Fig 1. 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 operates, go to next step. If fan does not operate, go to step 3).

  2. Check Triple-Pressure Switch Circuit

    Turn ignition off. Disconnect ECM harness connector. Check for continuity between ECM connector terminal No. 36 and triple-switch connector terminal No. 4. See Fig 4. Check for continuity between triple-switch connector terminal No. 3 and body ground. If continuity is as specified, go to next step. If continuity is not as specified, replace triple-switch.

  3. Check Power Supply

    Turn ignition off. Disconnect cooling fan relay. Refer to Fig 2. Turn ignition on. Measure voltage between ground and relay terminals No. 2 and No. 5. See Fig 5. If battery voltage is present, go to next step. If battery voltage is not present, repair harness or connectors between cooling fan relay and ignition switch.

  4. Check Ground Circuit

    Turn ignition off. Disconnect cooling fan motor harness connector. See Fig 3. Check for continuity between cooling fan connector terminal No. "1" and relay terminal No. 3. Check for continuity between cooling fan connector terminal No. "2" and body ground. See Fig 6. If continuity is present, go to next step. If continuity is not present, repair harness or connectors as necessary.

  5. Check Output Signal Circuit

    Leave ignition off, relay and cooling fan motor harness connector disconnected. Disconnect ECM harness connector. Check for continuity between relay terminal No. "1" and ECM connector terminal No. 14. See Fig 7. If continuity is present, go to next step. If continuity is not present, repair harness or connectors as necessary.

  6. Check Cooling Fan Relay

    Connect relay terminal No. "3" to ground. Using jumper wire, apply battery voltage to terminal No. 5. Check continuity as follows:
    • Verify continuity is present between relay terminals No. "1" and "2".

    Remove battery voltage from relay. Check continuity as follows:

    • Verify continuity is not present between relay terminals No. "1" and "2".

    If continuity is not as specified, replace cooling fan relay. If continuity is as specified, go to next step.

  7. Check Cooling Fan Motor

    With cooling fan motor disconnected, apply fused battery power to terminal of White/Green wire terminal. See Fig 1-Fig 7 . When ground is supplied to the other terminal, cooling fan motor should operate. If motor operates, testing is complete. If cooling fan motor does not operate, go to next step.
  8. Disconnect ECM wiring harness connector. Check connector pins for damage or corrosion. Check all circuit connectors for clean, tight fit and service if necessary. Loosen and retighten engine ground screws. See Fig 1-Fig 7 .
Fig 1: Locating Triple Switch Harness Connector (J30)
G96G10393Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 2: Locating Cooling Fan Relay (J30)
G96H10394Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 3: Locating Cooling Fan Motor Harness Connector (J30)
G96I10395Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 4: DTC P1900, Checking Triple-Pressure Switch Circuit (J30)
G96J10396Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 5: DTC P1900, Checking Power Supply Circuit (J30)
G96A10397Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 6: DTC P1900, Checking Ground Circuit (J30)
G96B10398Courtesy of NISSAN MOTOR CO., U.S.A.
Fig 7: DTC P1900, Checking Output Signal Circuit (J30)
G96C10399Courtesy of NISSAN MOTOR CO., U.S.A.
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