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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 365 (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 car, the 2011 GMC Yukon, 2011 Chevrolet Tahoe, and 2011 Cadillac Escalade. However, it is still accessible from the selected car via links, so may be relevant.
  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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