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HOMESERVICE MANUALSCHEVROLET2008CHEVY EXPRESS G3500, VAN PASSENGER EXTENDEDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT VARIANT/TRIMSECTION 13 (ENGINE CONTROL SYSTEM & FUEL SYSTEM - 4.3L - DTC P0340 TO DTC P2138)DTC P1516, P2101, P2119, OR P2176CIRCUIT/SYSTEM TESTING
2008 Chevrolet Chevy Express G3500, Van Passenger Extended

Circuit/System Testing

2008 Chevrolet Chevy Express G3500, Van Passenger ExtendedSECTION Circuit/System Testing
WARNING: This page is about a different variant/trim than selected.
CAUTION: Turn OFF the ignition before inserting fingers into the throttle bore. Unexpected movement of the throttle blade could cause personal injury.
  1. Inspect the throttle body for the following conditions:
    • A throttle blade that is NOT in the rest position
    • A throttle valve that is binding open or closed
    • A throttle blade that is free to move open or closed WITHOUT spring pressure
    • If a condition is found, replace the throttle body assembly.
    2. IMPORTANT: Disconnecting the throttle body harness connector causes additional DTCs to set.
  2. Ignition OFF, disconnect the harness connector at the throttle body.
  3. Ignition ON, verify that a test lamp does not illuminate between motor control 1 circuit terminal B and ground.
    • If test lamp illuminates, test the motor control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  4. Ignition ON, verify that a test lamp does not illuminate between motor control 2 circuit terminal A and ground.
    • If the test lamp illuminates, test the motor control circuit for a short to voltage. If the circuit tests normal, replace the ECM.
  5. Ignition ON, verify that a test lamp does not illuminate between motor control 1 circuit terminal B and B+.
    • If the test lamp illuminates, test the motor control circuit for a short to ground. If the circuit tests normal, replace the ECM.
  6. Ignition ON, verify that a test lamp does not illuminate between motor control 2 circuit terminal A and B+.
    • If the test lamp illuminates, test the motor control circuit for a short to ground. If the circuit tests normal, replace the ECM.
  7. Ignition OFF, allow sufficient time for the ECM to completely power down. Connect a DMM between the motor control 1 circuit terminal B and ground.
    8. IMPORTANT: When measuring peak voltage, ensure that the DMM is on the proper voltage scale and that the response time is set to 1 ms.
  8. Measure for B+ on the motor control 1 circuit terminal B as the ignition is turned ON.
    • If the peak voltage is not within 1 volt of B+, test the circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  9. Ignition OFF, allow sufficient time for the ECM to completely power down.
  10. Measure for B+ on the motor control 2 circuit terminal A as the ignition is turned ON.
    • If the peak voltage is not within 1 volt of B+, test the circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  11. If all circuits test normal, replace the throttle body.
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Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.