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Home >> GMC >> 2018 >> Acadia Denali, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 356 (Engine Controls And Fuel - 3.6L (LGX) - DTC P0446 To DTC P3436 And Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> DTC P159F or P15A0: Fuel Economy Mode Switch >> 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.
NOTE:

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

  1. Ignition OFF, disconnect the harness connector at the S126 drive mode select switch.
  2. NOTE:

    It may take up to 2 minutes for all vehicle systems to power down.

  3. Ignition OFF and all vehicle systems OFF, test for less than 5 Ω between ground circuit terminal 10 of the harness connector and ground.
    • If greater than the specified value, test the ground circuit for an open/high resistance and repair as necessary.
  4. Ignition ON, test for 4.8-5.2 V between 5 V reference circuit terminal 9 of the harness connector and ground.
    • If less than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 ECM.
    • If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.
  5. Ignition ON, test for 0.050-0.250 V between signal circuit terminal 7 of the harness connector and ground.
    • If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 ECM.
    • If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.
  6. If all circuits test normal, test or replace the S126 drive mode select switch.