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Home >> GMC >> 2018 >> Acadia Denali, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 335 (Mirror System) >> Diagnostic Information and Procedures >> Power Mirror Malfunction (With AAB) >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2017 GMC Acadia. However, it is still accessible from the selected car via links, so may be relevant.

Driver Outside Mirror Movement Malfunction

  1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the S79D Window Switch - Driver. It may take up to 2 minutes for all vehicle systems to power down.
  2. Test for less than 10 Ω between the ground circuit terminal 24 and ground.
    • If 10 Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
    • If less than 10 Ω 
  3. Ignition ON.
  4. Verify a test lamp illuminates between the B+ circuit terminal 23 and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the B+ circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.
    • If the test lamp does not illuminate and the circuit fuse is open 
    1. Ignition OFF.
    2. Test for infinite resistance between the B+ circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for infinite resistance between the control circuits listed below and ground:
      • Control circuit terminal 6
      • Control circuit terminal 7
      • Control circuit terminal 8
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the S79D Window Switch - Driver.
    • If the test lamp illuminates 
  5. Ignition OFF, connect the harness connector at the S79D Window Switch - Driver and disconnect the X510 inline harness connector at the A9A Outside Rearview Mirror-Driver. Ignition ON
  6. Connect a test lamp between the control circuit terminal 12 and control circuit terminal 9.
  7. Verify the test lamp turns ON when commanding the Up and Down states with a scan tool.
    • If the test lamp remains OFF during either of the commands 
    1. Ignition OFF, remove the test lamp, disconnect the harness connector at the S79D Window Switch - Driver.
    2. Test for infinite resistance between each control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in each control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the S79D Window Switch - Driver.
    • If the test lamp is always ON 
    1. Ignition OFF, remove the test lamp, disconnect the harness connector at the S79D Window Switch - Driver, ignition ON.
    2. Test for less than 1 V between each control circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the S79D Window Switch - Driver.
    • If the test lamp turns ON during each of the commands 
  8. Connect a test lamp between the control circuit terminal 12 and control circuit terminal 10.
  9. Verify the test lamp turns ON when commanding the Left and Right states with a scan tool.
    • If the test lamp remains OFF during either of the commands 
    1. Ignition OFF, remove the test lamp, disconnect the harness connector at the S79D Window Switch - Driver.
    2. Test for infinite resistance between each control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in each control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the S79D Window Switch - Driver.
    • If the test lamp is always ON 
    1. Ignition OFF, remove the test lamp, disconnect the harness connector at the S79D Window Switch - Driver, ignition ON.
    2. Test for less than 1 V between each control circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the S79D Window Switch - Driver.
    • If the test lamp turns ON during each of the commands 
  10. Test or replace the M77D Outside Rearview Mirror Motor-Driver.

Driver Mirror Position Sensor Circuit Test

  1. Ignition OFF and all vehicle systems OFF, disconnect the X510 inline harness connector at the A9A Outside Rearview Mirror-Driver. It may take up to 2 minutes for all vehicle systems to power down.
  2. Test for less than 10 Ω between the low reference circuit terminal 3 and ground.
    • If 10 Ω or greater 
    1. Ignition OFF, disconnect the harness connector at the S79D Window Switch - Driver.
    2. Test for less than 2 Ω in the low reference circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the S79D Window Switch - Driver.
    • If less than 10 Ω 
  3. Ignition ON.
  4. Test for 4.8-5.2 V between the 5 V reference circuit terminal 17 and ground.
    • If less than 4.8 V 
    1. Ignition OFF, disconnect the harness connector at the S79D Window Switch - Driver.
    2. Test for infinite resistance between the 5 V reference circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the 5 V reference circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the S79D Window Switch - Driver.
    • If greater than 5.2 V 
    1. Ignition OFF, disconnect the harness connector at the S79D Window Switch - Driver, ignition ON.
    2. Test for less than 1 V between the 5 V reference circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the S79D Window Switch - Driver.
    • If between 4.8-5.2 V 
  5. Verify the scan tool Driver Mirror Vertical Position parameter is less than 4.6 V.
    • If 4.6 V or greater 
    1. Ignition OFF, disconnect the X1 harness connector at the S79D Window Switch - Driver, ignition ON.
    2. Test for less than 1 V between the signal circuit terminal 18 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the S79D Window Switch - Driver.
    • If less than 4.6 V 
  6. Install a 3 A fused jumper wire between the signal circuit terminal 18 and the 5 V reference circuit terminal 17.
  7. Verify the scan tool Driver Mirror Vertical Position parameter is greater than 0.6 V.
    • If 0.6 V or less 
    1. Ignition OFF, remove the jumper wire, disconnect the harness connector at the S79D Window Switch - Driver.
    2. Test for infinite resistance between the signal circuit terminal 18 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the signal circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the S79D Window Switch - Driver.
    • If greater than 0.6 V 
  8. Verify the scan tool Driver Mirror Horizontal Position parameter is less than 4.6 V.
    • If 4.6 V or greater 
    1. Ignition OFF, disconnect the harness connector at the S79D Window Switch - Driver, ignition ON.
    2. Test for less than 1 V between the signal circuit terminal 16 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the S79D Window Switch - Driver.
    • If less than 4.6 V 
  9. Install a 3 A fused jumper wire between the signal circuit terminal 16 and the 5 V reference circuit terminal 17.
  10. Verify the scan tool Driver Mirror Horizontal Position parameter is greater than 0.6 V.
    • If 0.6 V or less 
    1. Ignition OFF, remove the jumper wire, disconnect the harness connector at the S79D Window Switch - Driver.
    2. Test for infinite resistance between the signal circuit terminal 16 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the signal circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the S79D Window Switch - Driver.
    • If greater than 0.6 V 
  11. Test or replace the M77D Outside Rearview Mirror Motor-Driver.

Passenger Outside Mirror Movement Malfunction

  1. Ignition OFF, disconnect the X610 inline harness connector at the A9B Outside Rearview Mirror-Passenger. Ignition ON
  2. Connect a test lamp between the control circuit terminal 9 and control circuit terminal 12.
  3. Verify the test lamp turns ON when commanding the Up and Down states with a scan tool.
    • If the test lamp remains OFF during either of the commands 
    1. Ignition OFF, remove the test lamp, disconnect the X2 harness connector at the S79P Window Switch-Passenger.
    2. Test for infinite resistance between each control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in each control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the S79P Window Switch-Passenger.
    • If the test lamp is always ON 
    1. Ignition OFF, remove the test lamp, disconnect the X2 harness connector at the S79P Window Switch-Passenger, ignition ON.
    2. Test for less than 1 V between each control circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the S79P Window Switch-Passenger
    • If the test lamp turns ON during each of the commands 
  4. Connect a test lamp between the control circuit terminal 10 and control circuit terminal 12.
  5. Verify the test lamp turns ON when commanding the Left and Right states with a scan tool.
    • If the test lamp remains OFF during either of the commands 
    1. Ignition OFF, remove the test lamp, disconnect the harness connector at the S79P Window Switch-Passenger.
    2. Test for infinite resistance between each control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in each control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the S79P Window Switch-Passenger.
    • If the test lamp is always ON 
    1. Ignition OFF, remove the test lamp, disconnect the harness connector at the S79P Window Switch-Passenger, ignition ON.
    2. Test for less than 1 V between each control circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the S79P Window Switch-Passenger
    • If the test lamp turns ON during each of the commands 
  6. Test or replace the M77P Outside Rearview Mirror Motor-Passenger.

Passenger Mirror Position Sensor Circuit Test

  1. Ignition OFF and all vehicle systems OFF, disconnect the X610 inline harness connector at the A9B Outside Rearview Mirror-Passenger. It may take up to 2 minutes for all vehicle systems to power down.
  2. Test for less than 10 Ω between the low reference circuit terminal 3 and ground.
    • If 10 Ω or greater 
    1. Ignition OFF, disconnect the harness connector at the S79P Window Switch-Passenger.
    2. Test for less than 2 Ω in the low reference circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the S79P Window Switch-Passenger.
    • If less than 10 Ω 
  3. Ignition ON.
  4. Test for 4.8-5.2 V between the 5 V reference circuit terminal 17 and ground.
    • If less than 4.8 V 
    1. Ignition OFF, disconnect the harness connector at the S79P Window Switch-Passenger.
    2. Test for infinite resistance between the 5 V reference circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the 5 V reference circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the S79P Window Switch-Passenger.
    • If greater than 5.2 V 
    1. Ignition OFF, disconnect the harness connector at the S79P Window Switch-Passenger, ignition ON.
    2. Test for less than 1 V between the 5 V reference circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the S79P Window Switch-Passenger.
    • If between 4.8-5.2 V 
  5. Verify the scan tool Passenger Mirror Vertical Position parameter is less than 4.6 V.
    • If 4.6 V or greater 
    1. Ignition OFF, disconnect the harness connector at the S79P Window Switch-Passenger, ignition ON.
    2. Test for less than 1 V between the signal circuit terminal 7 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the S79P Window Switch-Passenger.
    • If less than 4.6 V 
  6. Install a 3 A fused jumper wire between the signal circuit terminal 7 and the 5 V reference circuit terminal 6.
  7. Verify the scan tool Passenger Mirror Vertical Position parameter is greater than 0.6 V.
    • If 0.6 V or less 
    1. Ignition OFF, remove the jumper wire, disconnect the X2 harness connector at the S79P Window Switch-Passenger.
    2. Test for infinite resistance between the signal circuit terminal 7 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the signal circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the S79P Window Switch-Passenger.
    • If greater than 0.6 V 
  8. Verify the scan tool Passenger Mirror Horizontal Position parameter is less than 4.6 V.
    • If 4.6 V or greater 
    1. Ignition OFF, disconnect the harness connector at the S79P Window Switch-Passenger, ignition ON.
    2. Test for less than 1 V between the signal circuit terminal 9 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the S79P Window Switch-Passenger.
    • If less than 4.6 V 
  9. Install a 3 A fused jumper wire between the signal circuit terminal 9 and the 5 V reference circuit terminal 6.
  10. Verify the scan tool Passenger Mirror Horizontal Position parameter is greater than 0.6 V.
    • If 0.6 V or less 
    1. Ignition OFF, remove the jumper wire, disconnect the harness connector at the S79P Window Switch-Passenger.
    2. Test for infinite resistance between the signal circuit terminal 9 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the signal circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the S79P Window Switch-Passenger.
    • If greater than 0.6 V 
  11. Test or replace the M77P Outside Rearview Mirror Motor-Passenger.
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