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Home >> Chevrolet >> 2007 >> Chevy Express G2500, Van Cargo, 6.6 6 >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 15 (Engine Control System & Fuel System - 6.6L (LLY) - DTC P0401 To DTC P2510) >> DTC P2122, P2123, 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 APP sensor. Allow at least 60 seconds for the ECM to power down.
  2. Ignition OFF, test for less than 2 ohms of resistance between each low reference circuit terminals 4 and 5 and ground.
    • If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  3. Ignition ON, test for 4.8-5.2 volts between each APP sensor 5-volt reference circuit terminals 1 and 2 and ground.
    • If less than the specified range, test the affected 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
    • If greater than the specified range, test the affected 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  4. Verify that the scan tool APP Sensor 1 and Sensor 2 parameters are less than 0.02 volt.
    • If greater than 0.02 volt, test the applicable signal circuit terminals 3 or 6 for a short to voltage. If the circuit tests normal, replace the ECM.
  5. Install a 3A fused jumper wire between each signal circuit terminals 3 or 6 and the 5-volt reference circuit. Verify that the scan tool APP Sensor parameter is greater than 4.57 volts.
    • If less than the specified range, test the applicable signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the ECM.
  6. Ignition OFF, disconnect the harness connector at the ECM.
  7. Test for less than 5 ohms of resistance on all APP sensor circuits between the following terminals:
    • The ECM C2 signal circuit terminal 49 to APP terminal 3
    • The ECM C1 signal circuit terminal 21 to APP terminal 6
    • The ECM C1 5-volt reference circuit terminal 38 to APP terminal 1
    • The ECM C2 5-volt reference circuit terminal 15 to APP terminal 2
    • If greater than 5 ohms, repair the affected circuit for open/high resistance.
  8. Test for infinite resistance between APP sensor 1 and 2 signal circuits.
    • If less than infinite resistance, repair the short between signal circuits.
  9. If all circuits test normal, test the accelerator pedal assembly. Refer to Component Testing for instructions.
    • If the APP sensor tests normal, replace the ECM.
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