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Home >> GMC >> 2011 >> Yukon Base, 5.3 3 >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 14 (Engine Controls And Fuel - Hybrid (LZ1) - DTC P0351 Through DTC P3449 And Troubleshooting) >> Diagnostic Information and Procedures >> DTC P2120, P2122, P2123, P2125, P2127, P2128, or P2138 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.
  1. Ignition OFF, disconnect the harness connector at the accelerator pedal.
  2. Ignition OFF for 2 minutes and the scan tool powered OFF, test for less than 5 Ω between the appropriate low reference circuit terminal listed below and ground.
    • APP sensor 1 terminal F
    • APP sensor 2 terminal A
    • If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit/connections test normal, replace the ECM.
  3. Ignition ON, test for 4.8-5.2 V between the appropriate 5-volt reference circuit terminal listed below and ground.
    • APP sensor 1 terminal D
    • APP sensor 2 terminal C
    • If less than the specified range, test the 5-volt reference circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the ECM.
    • If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  4. Verify the scan tool APP sensor 1 and 2 voltages are less than 0.3 V.
    • If greater than the specified range, test the APP sensor 1 and 2 signal circuits terminals B and E for a short to voltage. If the circuit tests normal, replace the ECM.
  5. Install a 3 A fused jumper wire between the APP sensor 1 signal circuit terminal E and the 5-volt reference circuit terminal D. Verify the scan tool APP sensor 1 voltage parameter is greater than 4.8 V.
    • If less than the specified range, test the APP sensor 1 signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
  6. Install a 3 A fused jumper wire between the APP sensor 2 signal circuit terminal B and the 5-volt reference circuit terminal D. Verify the scan tool APP sensor 2 voltage parameter is greater than 4.8 V.
    • If less than the specified range, test the APP sensor 2 signal circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the ECM.
  7. If all circuits and connections test normal, test or replace the Accelerator Pedal Position Sensor.
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