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Home >> Nissan-Datsun >> 2021 >> NV2500 HD S >> Repair and Diagnosis >> External Pages >> Different car >> Section 53 (Defogger System (Circuit Diagnosis)) >> Circuit Diagnosis >> Rear Window Defogger Switch >> Diagnosis Procedure

Diagnosis Procedure

WARNING: This page is about a different car, the 2018 Nissan Maxima. However, it is still accessible from the selected car via links, so may be relevant.
  1. CHECK REAR WINDOW DEFOGGER RELAY OPERATION 
    1. Push the ignition switch to ON.
    2. Check that an operation noise of rear window defogger relay [located in fuse block (J/B)] can be heard when pressing the rear window defogger switch ON and OFF.

    Is the inspection result normal?

    YES

    GO TO 2.

    NO

    GO TO 5.

  2. CHECK FUSE 

    Check if fuse 22 from the rear window defogger relay output is blown.

    Is the fuse blown?

    YES

    Replace the blown fuse after repairing the affected circuit.

    NO

    GO TO 3.

  3. CHECK FOR VOLTAGE FROM THE REAR WINDOW DEFOGGER RELAY 
    1. Press rear window defogger switch.
    2. Check for voltage between fuse block (J/B) connector and ground.

      (+)

      (-)

      Condition

      Voltage (V)

      (Approx.)

      Fuse block (J/B)

      Connector

      Terminal

      M5

      4P

      Ground

      Rear window defogger switch

      ON

      Battery voltage

      OFF

      0

    Is the inspection result normal?

    YES

    GO TO 4.

    NO

    Perform rear window defogger relay diagnosis. Refer to Diagnosis Procedure .

  4. CHECK REAR WINDOW DEFOGGER SWITCH INDICATOR CIRCUIT 
    1. Press rear window defogger switch.
    2. Check for voltage between A/C auto amp. connector and ground.

      (+)

      (-)

      Condition

      Voltage (V)

      (Approx.)

      A/C auto amp.

      Connector

      Terminal

      M37

      35

      Ground

      Rear window defogger switch

      ON

      Battery voltage

      OFF

      0

    Is the inspection result normal?

    YES

    Replace A/C auto amp. Refer to Removal and Installation .

    NO

    Repair or replace harness.

  5. CHECK A/C AUTO AMP. (REAR WINDOW DEFOGGER SWITCH) FUNCTION 

    SYMBOL CONSULT

    1. Select "REAR DEFOGGER" of "BCM".
    2. Select "REAR DEF SW" in "Data Monitor" mode.
    3. Check that the function operates normally according to the following conditions:

    Monitor Item

    Condition

    Status

    REAR DEF SW

    Rear window defogger switch

    Pressed

    On

    Released

    Off

    Is the inspection result normal?

    YES

    GO TO 8.

    NO

    GO TO 6.

  6. CHECK REAR WINDOW DEFOGGER ON SIGNAL CIRCUIT 

    Check voltage between BCM connector and ground.

    (+)

    (-)

    Condition

    Voltage (V)

    (Approx.)

    BCM

    Connector

    Terminal

    M21

    32

    Ground

    Rear window defogger switch

    ON

    0

    OFF

    5

    Is the inspection result normal?

    YES

    Replace BCM. Refer to Removal and Installation .

    NO

    GO TO 7.

  7. CHECK HARNESS CONTINUITY 
    1. Push ignition switch to OFF.
    2. Disconnect BCM and A/C auto amp.
    3. Check continuity between BCM connector and A/C auto amp.

      BCM

      A/C auto amp.

      Continuity

      Connector

      Terminal

      Connector

      Terminal

      M21

      32

      M37

      15

      Yes
    4. Check continuity between BCM harness connector and ground.

      BCM

      Ground

      Continuity

      Connector

      Terminal

      M21

      32

      No

    Is the inspection result normal?

    YES

    Replace A/C auto amp. Refer to Removal and Installation .

    NO

    Repair or replace harness.

  8. CHECK REAR WINDOW DEFOGGER RELAY GROUND CIRCUIT 

    SYMBOL CONSULT

    1. Select "REAR DEFOGGER" of "BCM".
    2. Select "REAR DEFOGGER" in "Active Test" mode.
    3. Turn rear defogger active test ON and OFF.
    4. Check voltage between fuse block (J/B) connector and ground.

      (+)

      (-)

      Condition

      Voltage (V)

      (Approx.)

      Fuse block (J/B)

      Connector

      Terminal

      M5

      6P

      Ground

      Rear window defogger active test

      ON

      0

      OFF

      Battery voltage

    Is the inspection result normal?

    YES

    GO TO 11.

    NO

    GO TO 9 .

  9. CHECK REAR WINDOW DEFOGGER RELAY CIRCUIT 

    Check voltage between fuse block (J/B) connector and ground.

    (+)

    (-)

    Condition

    Voltage (V)

    (Approx.)

    Fuse block (J/B)

    Connector

    Terminal

    M5

    6P

    Ground

    Rear window defogger switch

    ON

    0

    OFF

    Battery voltage

    Is the inspection result normal?

    YES

    Replace rear window defogger relay.

    NO

    GO TO 10.

  10. CHECK HARNESS CONTINUITY 
    1. Push ignition switch to OFF.
    2. Disconnect BCM and fuse block (J/B).
    3. Check continuity between BCM connector and fuse block (J/B) connector.

      BCM

      Fuse block (J/B)

      Continuity

      Connector

      Terminal

      Connector

      Terminal

      M20

      61

      M5

      6P

      Yes
    4. Check continuity between fuse block (J/B) connector and ground.

    Fuse block (J/B)

    Ground

    Continuity

    Connector

    Terminal

    M5

    6P

    No

    Is the inspection result normal?

    YES

    Perform rear window defogger relay component inspection. Refer to Component Inspection . If OK, replace BCM. Refer to Removal and Installation .

    NO

    Repair or replace harness.

  11. CHECK REAR WINDOW DEFOGGER RELAY 

    Check rear window defogger relay. Refer to Component Inspection .

    Is the inspection result normal?

    YES

    GO TO 12 .

    NO

    Replace rear window defogger relay.

  12. CHECK INTERMITTENT INCIDENT 

    Check intermittent incident. Refer to Intermittent Incident .

    Is the inspection result normal?

    YES

    Check the following:

    • Battery power supply circuit
    • Fuse block (J/B)

    NO

    Repair or replace the malfunctioning parts.

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