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Home >> GMC >> 2018 >> Acadia Denali, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 279 (Engine Controls And Fuel - 2.0L (LTG) - DTC P0300 To DTC P2635 And Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> DTC P159F or P15A0: Fuel Economy Mode Switch (Automatic Transmission) >> 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.
NOTE:

You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

  1. Ignition OFF and all vehicle systems OFF, It may take up to 2 minutes for all vehicle systems to power down.
  2. Disconnect the harness connector at the S126 Drive Mode Select switch.
  3. Test for 266-294 Ω between terminal 5 of the switch and terminal 2 of the switch.
    • If not within the specified range 

      Replace the S126 Drive Mode Select switch.

    • If within the specified range 
  4. Test for 1,414-1,562 Ω between terminal 5 of the switch and terminal 9 of the switch.
    • If not within the specified range 

      Replace the S126 Drive Mode Select switch.

    • If within the specified range 
  5. With the S126 Drive Mode Select switch button depressed, test for 486-538 Ω between terminal 5 of the switch and terminal 9 of the switch.
    • If not within the specified range 

      Replace the S126 Drive Mode Select switch.

    • If within the specified range 
  6. Test for less than 5 Ω between the ground circuit terminal 9 of the harness connector and ground.
    • If 5 Ω or greater 

      Repair the open/high resistance in the circuit.

    • If less than 5 Ω 
  7. Ignition ON.
  8. Test for 4.8-5.2 V between the 5 V reference circuit terminal 5 of the harness connector and ground.
    • If less than 4.8 V 
    1. Ignition OFF, disconnect the X2 harness connector at the K20 Engine Control Module.
    2. Test for infinite resistance between the 5 V reference circuit and ground.
      • If less than infinite resistance, repair the short to ground in 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 K20 engine control module.
    • If greater than 5.2 V 
    1. Ignition OFF, disconnect the X2 harness connector at the K20 Engine Control Module.
    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 in the circuit.
      • If less than 1 V, replace the K20 Engine Control Module.
    • If within 4.8-5.2 V 
    1. Ignition OFF, disconnect the X2 harness connector at the K20 Engine Control Module.
    2. Test for less than 1 V between the signal circuit and ground.
      • If 1 V or greater, repair the short to voltage in the circuit.
      • If less than 1 V
    3. Test for infinite resistance between the signal circuit and ground.
      • If less than infinite resistance, repair the short to ground in the circuit.
      • If infinite resistance
    4. 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
  9. Replace the K20 Engine Control Module.
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