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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 31 (ENGINE CONTROLS - 6.6L - DIAGNOSIS (DTCs P0402-P2636)) >> DTC P2122, P2123, P2127, P2128, or P2138 >> Circuit/System Testing

Circuit/System Testing

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P2122, P2123, P2127, or P2128

  1. With the ignition ON, observe the APP sensor 1 voltage parameter with the accelerator pedal in the released position. Verify the voltage is between 0.89-4.57 volts.
    • If more than 4.57 volts, test the APP sensor 1 low reference circuit for an open or a faulty ECM.
    • If less than 0.80 volts, test the APP sensor 1 signal circuit for an open, a short to ground, or a faulty ECM.
  2. With the ignition ON, observe the APP sensor 2 voltage parameter with the accelerator pedal in the released position. Verify the voltage is between 0.41-2.19 volts.
    • If more than 2.5 volts, test the low reference for an open or a faulty ECM.
    • If less than 0.3 volts, test the APP sensor 2 signal circuit for an open, a short to ground, or a faulty ECM.
  3. Disconnect the accelerator pedal harness connector and verify that APP sensor 1 and 2 voltages are less than 0.1 volts.
    • If more than 01 volts, test the APP sensor 1 and 2 signal circuits for a short to voltage or a faulty ECM.
  4. With the ignition ON, test for 4.8-5.2 volts between each 5-volt reference circuits and a good ground.
    • If more than 5.2 volts, test the affected 5-volt reference circuit for a short to voltage, or faulty ECM.
    • If less than 4.8 volts, test the affected 5-volt reference circuit for an open or short to ground, or a faulty ECM.
  5. Install a 3-amp fused jumper wire between the signal circuit and the 5-volt reference circuit of the APP sensor 1, and verify the APP sensor 1 voltage is greater than 4.8 volts.
    • If less than 4.8 volts test the APP sensor 1 signal circuit for an open, short to ground, or a faulty ECM.
  6. Install a 3-amp fused jumper wire between the signal circuit and the 5-volt reference circuit of the APP sensor 2, and verify that the APP sensor 2 voltage is greater than 4.8 volts.
    • If less than 4.8 volts, test the APP sensor 2 signal circuit for an open, short to ground, or a faulty ECM.
  7. With the ignition OFF, the APP sensor and the ECM harness connectors disconnected, test for infinite resistance between APP sensor 1 signal circuit and APP sensor 2 signal circuit.
    • If infinite resistance, repair the short between APP sensor 1 signal circuit and APP sensor 2 signal circuit.
  8. If all circuits test normal, replace the accelerator pedal.

P2138

  1. With the ignition OFF, disconnect the accelerator pedal and the ECM harness connectors. With a DMM, measure for a resistance value of less than 5 ohms on each APP sensor circuit.
    • If more than 5 ohms, repair the circuit with the high resistance.
    • If less than 5 ohms, test for a short between APP sensor 1 signal circuit and APP sensor 2 signal circuit.
  2. If all circuits test normal, replace the accelerator pedal assembly.
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