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Circuit/System Testing

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Turn Signal/Multifunction Switch Malfunction

  1. Ignition OFF, scan tool disconnected, all doors closed, all accessories OFF, disconnect the harness connector at the S78 Turn Signal/Multifunction Switch. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 5 Ω between the ground circuit terminal 1 and ground.
    • If 5 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 5 Ω 
  3. Ignition ON.
  4. Verify the scan tool Left Turn Signal Switch parameter is Inactive.
    • If not Inactive 
    1. Ignition OFF, disconnect the X1 harness connector at the K9 Body Control Module.
    2. Test for infinite resistance between the signal circuit terminal 2 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the K9 Body Control Module.
    • If Inactive 
  5. Install a 3 A fused jumper wire between the signal circuit terminal 2 and ground.
  6. Verify the scan tool Left Turn Signal Switch parameter is Active.
    • If not Active 
    1. Ignition OFF, disconnect the X1 harness connector at the K9 Body Control Module, ignition ON.
    2. Test for less than 1 V between the signal circuit terminal 2 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V
    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 K9 Body Control Module.
    • If Active 
  7. Verify the scan tool Right Turn Signal Switch parameter is Inactive.
    • If not Inactive 
    1. Ignition OFF, disconnect the X1 harness connector at the K9 Body Control Module.
    2. Test for infinite resistance between the signal circuit terminal 3 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the K9 Body Control Module.
    • If Inactive 
  8. Install a 3 A fused jumper wire between the signal circuit terminal 3 and ground.
  9. Verify the scan tool Right Turn Signal Switch parameter is Active.
    • If not Active 
    1. Ignition OFF, disconnect the X1 harness connector at the K9 Body Control Module, ignition ON.
    2. Test for less than 1 V between the signal circuit terminal 3 and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V
    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 K9 Body Control Module.
    • If Active 
  10. Test or replace the S78 Turn Signal/Multifunction Switch.

Turn Signal Lamps Malfunction

  1. Ignition OFF, exterior lamps OFF, disconnect the harness connector at the appropriate turn signal lamp.
  2. Test for less than 5 Ω between the appropriate ground circuit terminal listed below and ground.
    • E4LF Turn Signal Lamp - Left Front socket terminal (Z88/W49)
    • A9A Outside Rearview Mirror - Driver terminal 10 (Z88/W49/X88)
    • E4RF Turn Signal Lamp - Right Front socket terminal (Z88/W49)
    • A9B Outside Rearview Mirror - Passenger terminal 10 (Z88/W49/X88)
    • E4N Park/Turn Signal Lamp - Left terminal C (X88)
    • E4P Park/Turn Signal Lamp - Right terminal C (X88)
    • E4LR Turn Signal Lamp - Left Rear socket terminal (X88)
    • E4RR Turn Signal Lamp - Right Rear socket terminal (X88)
    • E42L Tail Lamp Assembly - Left terminal 4 (Z88)
    • E42L Tail Lamp Assembly - Left terminal E (W49 with T89)
    • E42R Tail Lamp Assembly - Right terminal 4 (Z88)
    • E42R Tail Lamp Assembly - Right terminal E (W49 with T89)
    • If 5 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 5 Ω 
  3. Connect a test lamp between the appropriate control circuit terminal listed below and ground, ignition ON.
    • E4LF Turn Signal Lamp - Left Front socket terminal (Z88/W49)
    • A9A Outside Rearview Mirror - Driver terminal 5 (Z88/W49/X88)
    • E4RF Turn Signal Lamp - Right Front socket terminal (Z88/W49)
    • A9B Outside Rearview Mirror - Passenger terminal 5 (Z88/W49/X88)
    • E4N Park/Turn Signal Lamp - Left terminal B (X88)
    • E4P Park/Turn Signal Lamp - Right terminal B (X88)
    • E4LR Turn Signal Lamp - Left Rear socket terminal (X88)
    • E4RR Turn Signal Lamp - Right Rear socket terminal (X88)
    • E42L Tail Lamp Assembly - Left terminal 3 (Z88)
    • E42L Tail Lamp Assembly - Left terminal D (W49 with T89)
    • E42R Tail Lamp Assembly - Right terminal 3 (Z88)
    • E42R Tail Lamp Assembly - Right terminal D (W49 with T89)
  4. Verify the test lamp turns ON and OFF when commanding the appropriate Turn Signal Lamp ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the appropriate harness connector listed below at the K9 Body Control Module.
      • X5 left front turn signals and rear turn signals
      • X4 right front turn signals
    2. Test for infinite resistance between the 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 the 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 K9 Body Control Module.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the appropriate harness connector listed below at the K9 Body Control Module, ignition ON.
      • X5 left front turn signals and rear turn signals
      • X4 right front turn signals
    2. Test for less than 1 V between the control circuit terminal and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K9 Body Control Module.
    • If the test lamp turns ON and OFF 
  5. Test or replace the appropriate turn signal lamp.

Turn Signal Lamp Outage Detection Malfunction (Z88/W49 with T89)

  1. Ignition OFF, disconnect the harness connector at the appropriate component listed below, ignition ON.
    • E42L Tail Lamp Assembly - Left
    • E42R Tail Lamp Assembly - Right
  2. Test for B+ between the appropriate signal circuit terminal listed below and ground.
    • E42L Tail Lamp Assembly - Left terminal 2 (Z88)
    • E42R Tail Lamp Assembly - Right terminal 2 (Z88)
    • E42L Tail Lamp Assembly - Left terminal F (W49 with T89)
    • E42R Tail Lamp Assembly - Right terminal F (W49 with T89)
    • If not B+ 
    1. Ignition OFF, disconnect the appropriate harness connector listed below at the K9 Body Control Module.
      • X5 left rear turn signal
      • X2 right rear turn signal
    2. Test for infinite resistance between the signal 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 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 K9 Body Control Module.
    • If B+ 
  3. Verify a test lamp does not illuminate between the appropriate signal circuit terminal listed below and ground.
    • E42L Tail Lamp Assembly - Left terminal 2 (Z88)
    • E42R Tail Lamp Assembly - Right terminal 2 (Z88)
    • E42L Tail Lamp Assembly - Left terminal F (W49 with T89)
    • E42R Tail Lamp Assembly - Right terminal F (W49 with T89)
    • If the test lamp illuminates 
    1. Ignition OFF, disconnect the appropriate harness connector listed below at the K9 Body Control Module, ignition ON.
      • X5 left rear turn signal
      • X2 right rear turn signal
    2. Test for less than 1 V between the signal circuit terminal and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K9 Body Control Module.
    • If the test lamp does not illuminate 
  4. Test or replace the appropriate turn signal lamp.

Turn Signal Indicators Malfunction

  1. Ignition ON.
  2. Verify the left and right turn signal indicators turn ON and OFF while commanding the All Indicators Test ON and OFF with a scan tool.
    • If the left or right turn signal indictors are always OFF or remain ON 

      Replace the P16 Instrument Cluster.

    • If the left and right turn signal indictors turn ON and OFF 
  3. Replace the K9 Body Control Module.
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