Mirror System: Diagnosis GMC Cutaway G3500

Visual/Physical Inspection

An understanding of both the outside and automatic day-night mirror operation must be understood before reviewing the symptom tables. Refer to Outside Mirror Description and Operation (Power Mirrors) , Outside Mirror Description and Operation (Heated Mirrors) , or Automatic Day-Night Mirror Description and Operation .

1. Inspect for aftermarket devices which could affect the operation of the system. Refer to «Checking Aftermarket Accessories»(ref-478470-S29654985132012061100000) .
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. «Heated Mirrors Malfunction»(ref-478476-S03055728782012061100000)
2. «Automatic Day-Night Mirrors Malfunction»(ref-478476-S02495833052012061100000)
3. «Power Mirror Malfunction»(ref-478476-S06242521292012061100000)

Diagnostic Instructions

1. Perform the «Diagnostic System Check - Vehicle»(ref-478441-S40412187692012061100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-478441-S09524533772012061100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-478441-S05742973822012061100000) provides an overview of each diagnostic category.

Diagnostic Fault Information

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the appropriate outside rearview mirror.
2. Test for less than 10 ohms between the ground circuit terminal A and ground. If greater than the specified range, test the low reference circuit for an open/high resistance.
3. Connect a test lamp between the heater element control circuit terminal C and ground.
4. Ignition ON, operate the rear window defogger ON and OFF with the rear defogger switch. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to voltage. If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance.
5. If all circuits test normal, test or replace the outside rearview mirror glass.

1. Perform the «Diagnostic System Check - Vehicle»(ref-478441-S40412187692012061100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-478441-S09524533772012061100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-478441-S05742973822012061100000) provides an overview of each diagnostic category.

1. Ignition OFF, disconnect the harness connector at the inside rearview mirror.
2. Verify that a test lamp illuminates between B+ and the ground circuit terminal 8. If the test lamp does not illuminate, test the ground circuit for an open/high resistance.
3. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 13 and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.
4. Ignition ON, park brake applied, vehicle in REVERSE, verify that a test lamp illuminates between the backup lamp control circuit terminal 9 and ground. If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, refer to «Backup Lamps Malfunction»(ref-478448-S40083311772012061100000) .
5. If all circuits test normal, test or replace the inside rearview mirror.

1. Perform the «Diagnostic System Check - Vehicle»(ref-478441-S40412187692012061100000) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(ref-478441-S09524533772012061100000) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(ref-478441-S05742973822012061100000) provides an overview of each diagnostic category.

1. Ignition OFF, disconnect the harness connector at the power mirror switch.
2. Test for less than 10 ohms between the ground circuit terminal D and ground. If greater than the specified range, test the low reference circuit for an open/high resistance.
3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal E and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuits for a short to ground.
4. Connect the harness connector at the outside rearview mirror switch.
5. Disconnect the harness connector at the appropriate power mirror.
6. Connect a test lamp between the control circuit terminal F and the control circuit terminal E.
7. Operate the vertical switch UP and DOWN. The test lamp should turn ON when commanding the UP and DOWN states. If the test lamp remains OFF during either of the commands, test for a short to voltage, short to ground or an open/high resistance on the control circuits. If the circuits test normal, replace the power mirror switch.
8. Connect a test lamp between the control circuit terminal G and the control circuit terminal H.
9. Operate the horizontal switch LEFT and RIGHT. The test lamp should turn ON when commanding the LEFT and RIGHT states. If the test lamp remains OFF during either of the commands, test for a short to voltage, short to ground or an open/high resistance on the control circuits. If the circuits test normal, replace the power mirror switch.
10. If all circuits test normal, test or replace the power mirror.

Component Testing

Outside Rearview Mirror Switch

1. Ignition OFF, disconnect the harness connector at the outside rearview mirror switch.
2. Test for infinite resistance between all of the control circuit terminals and the B+ and ground circuit terminals with the switch in the open position. If less than the specified range, replace the power mirror switch.
3. Test for less than 1 ohms between all of the control terminals and ground terminal with the outside rearview mirror switch in the proper positions. If greater than the specified range, test the ground circuit for an open/high resistance. If the circuits test normal, replace the power mirror switch.