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Home >> GMC >> 2010 >> Terrain SLT, 2.4 W, AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System & Fuel System - 2.2L Or 2.4L - DTC P1255 To DTC P2635 >> DTC P159F or P15A0 >> Circuit/System Testing

Circuit/System Testing

NOTE: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
  1. Ignition OFF, disconnect the X1 harness connector at the Fuel Economy Mode switch.
  2. Test for less than 5 Ω between the ground circuit terminal 1 of the harness connector and ground.
    • If greater than the specified range, test the ground circuit for a open/high resistance and repair as necessary.
  3. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal 3 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.
  4. Observe the scan tool Fuel Economy Mode Switch parameter. The parameter should display Circuit Low Voltage.
    • If the parameter does not display the specified value, test the signal circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.
  5. Connect a 3 A fused jumper wire between 5 V reference circuit terminal 3 of the harness connector and signal circuit terminal 4 of the harness connector. Verify the scan tool Fuel Economy Mode Switch parameter displays Circuit High Voltage.
  6. If all scan tool parameter displays are normal, test or replace the S87 fuel economy mode switch.
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