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Home >> GMC >> 2018 >> Acadia Denali, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 180 (Battery, Charging System And Starting System) >> Diagnostic Information and Procedures >> Stop/Start System Malfunction (KL9 with M3L) >> Circuit/System Testing

Circuit/System Testing

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

ECO Switch Circuit Malfunction

  1. Ignition OFF, disconnect the harness connector at the S48A Multifunction Switch - Instrument Panel ignition ON.
  2. Verify the scan tool Stop/Start Select Switch parameter is Inactive.
    • If not Inactive 
    1. Ignition OFF, disconnect the harness connector at the K9 Body Control Module.
    2. Test for infinite resistance between the signal circuit terminal 10 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 
  3. Install a 3 A fused jumper wire between the signal circuit terminal 10 and ground.
  4. Verify the scan tool Stop/Start Select Switch parameter is Active.
    • If not Active 
    1. Ignition OFF, disconnect the harness connector at the K9 Body Control Module, ignition ON.
    2. Test for less than 1 V between the signal circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V
    3. Ignition OFF.
    4. Test for less than 2 Ω in the signal circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance on the circuit.
      • If less than 2 Ω, replace the K9 Body Control Module.
    • If Active 
  5. Test or replace the S48A Multifunction Switch - Instrument Panel.

ECO Switch Indicator Circuit Malfunction

  1. Ignition OFF, disconnect the harness connector at the S48A Multifunction Switch - Instrument Panel ignition ON.
  2. Connect a test lamp between the control circuit terminal 4 and B+.
  3. Verify the test lamp turns ON and OFF when commanding the Start/Stop Select Switch Indicator Active and Inactive with a scan tool.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the harness connector at the K9 Body Control Module.
    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, replace the K9 Body Control Module.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the harness connector at the K9 Body Control Module, ignition ON.
    2. Test for less than 1 V between the control circuit 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 on the circuit.
      • If less than 2 Ω, replace the K9 Body Control Module.
    • If the test lamp turns ON and OFF 
  4. Test or replace the S48A Multifunction Switch - Instrument Panel.

Power Supply Transformer Circuit Malfunction

  1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the T19 Power Supply Transformer. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 10 Ω between the ground circuit terminal 1 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 2 and ground.
    • If the test amp 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 T19 Power Supply Transformer control circuit terminal 4 and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, test or replace the T19 Power Supply Transformer.
      • If the test lamp illuminates 
  5. Verify a test lamp illuminates between the ignition circuit terminal 5 and ground.
    • If the test lamp does not illuminate 
    1. Ignition OFF.
    2. Test for infinite resistance between the ignition circuit and ground.
    • If the test lamp illuminates 
  6. Test or replace the T19 Power Supply Transformer.
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