Section 01-09: Mirrors, Rear View
1994 Mustang Workshop Manual
DIAGNOSIS AND TESTING

Pinpoint Tests

  

PINPOINT TEST A: BOTH LH AND RH MIRRORS DO NOT OPERATE

 

A1 CHECK SUPPLY AND GROUND

Yes
GO to A6 .

No
GO to A2 .

 

A2 CHECK GROUND CONTINUITY

Yes
GO to A3 .

No
SERVICE open in Circuit 57 (BK). REPEAT A1 .

 

A3 CHECK SUPPLY

  • Measure voltage between Circuit 54 (LG/Y) and known good ground.
  • Does voltage read 10 volts or more?
Yes
GO to A6 .

No
GO to A4 .

 

A4 CHECK SUPPLY SHORT TO GROUND

  • Measure resistance between Circuit 54 (LG/Y) and a known good ground.
  • Is resistance 100 k ohms or more?
Yes
GO to A5 .

No
SERVICE short to ground Circuit 54 (LG/Y). REPEAT A4 .

 

A5 CHECK SUPPLY CONTINUITY

  • Check continuity of Circuit 54 (LG/Y) between mirror control switch connector and instrument panel fuse panel, Fuse 8.
  • Is resistance less than 5 ohms?
Yes
REPLACE instrument panel fuse 8. GO to A6 .

No
SERVICE open Circuit 54 (LG/Y). REPEAT A5.

 

A6 CHECK SWITCH OPERATION

  • Using a jumper wire jump Circuit 54 (LG/Y) to appropriate circuits. Refer to Wire Harness Connector End View.
  • Observe operation of each outside rear view mirror as jumper is applied.
  • Did mirrors operate properly?
Yes
REPLACE outside rear view mirror control . RESTORE vehicle. RETEST system.

No
GO to A7 .

 

A7 CHECK OUTSIDE REAR VIEW MIRROR CONTROL OUTPUT FOR SHORT TO GROUND

  • Measure resistance between the following circuits and a known good ground.

    LH OUTSIDE REAR VIEW MIRROR
    Pin Circuit Function
    3 541 (DB) Up
    6 542 (Y) Down
    6 542 (Y) Right
    4 540 (R) Left



    RH OUTSIDE REAR VIEW MIRROR
    Pin Circuit Function
    7 544 (P) Up
    6 542 (Y) Down
    6 542 (Y) Right
    8 543 (DG) Left

  • Is resistance 100 k ohms or more?
Yes
RESTORE vehicle. RETEST system.

No
SERVICE suspect circuit. REPEAT A7 .

  

PINPOINT TEST B: SINGLE MIRROR DOES NOT OPERATE

 

B1 CHECK MIRROR UP/DOWN OPERATION

  • Remove glass from inoperative outside rear view mirror .
  • Disconnect motor wiring connector.
  • Connect test lamp between up/down circuits.
      LH outside rear view mirror 541(DB), 542 (Y)RH outside rear view mirror 544 (P), 542 (Y)
    • Actuate outside rear view mirror control up/down.
    • Did test lamp illuminate?
    Yes
    GO to B2 .

    No
    GO to B3 .

     

    B2 CHECK MIRROR LEFT/RIGHT OPERATION

    • Connect test lamp between left/right circuits. LH mirror 540 (R), 542 (Y)RH mirror 543 (DG), 542 (Y)
    • Actuate outside rear view mirror control left/right.
    • Did test lamp illuminate?
    Yes
    REPLACE outside rear view mirror . RESTORE vehicle. RETEST system.

    No
    GO to B3 .

     

    B3 CHECK SUSPECT CIRCUIT FOR VOLTAGE

    • Remove front door trim panel finish panel as outlined.
    • Disconnect mirror harness connector.
    • Connect test lamp between suspect circuit and a known good ground.
    • Actuate outside rear view mirror control in operative direction.
    • Did test lamp illuminate?
    Yes
    REPLACE mirror wiring harness. RESTORE vehicle. RETEST system.

    No
    SERVICE circuit from door to mirror switch. RESTORE vehicle. RETEST system.

      

    PINPOINT TEST C: SINGLE MIRROR DOES NOT FUNCTION WITH SWITCH LOGIC

     

    C1 CHECK POWER MIRROR SYSTEM LOGIC

    • Remove front door trim panel on vehicle side with malfunction.
    • Using a volt/ohmmeter, verify circuit logic at harness connector. Refer to the following diagram:
    • Actuate outside rear view mirror control .





      LH OUTSIDE MIRROR
      Pin Number Circuit Circuit Function
      1 540 (R) LH Mirror Left/Right Motor
      2 541 (DB) LH Mirror Up/Down Motor
      3 542 (Y) LH Remote Mirror Solenoid Control



      RH OUTSIDE MIRROR
      Pin Number Circuit Circuit Function
      1 543 (DG) RH Mirror Left/Right Motor
      2 544 (P) RH Mirror Up/Down Motor
      3 545 (W) RH Remote Mirror Solenoid Control

    • Is circuit logic OK?
    Yes
    REPLACE outside rear view mirror . RESTORE vehicle. RETEST system.

    No
    GO to C2 .

     

    C2 CHECK SUSPECT CIRCUIT LOGIC

    • Remove outside rear view mirror control . Leave harness connected to outside rear view mirror control .
    • Back-probe switch harness connector while adjusting outside rear view mirror control .
    • Test suspect circuit at switch connector.
    • Is circuit logic OK?
    Yes
    SERVICE crossed wires in harness. RESTORE vehicle. RETEST system.

    No
    REPLACE outside rear view mirror control. RESTORE vehicle. RETEST system.