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Home >> Chevrolet >> 2006 >> Cobalt LTZ >> Repair and Diagnosis >> External Pages >> Different car >> Section 793 (Engine Controls And Fuel - 2.0L - DTC P0243 To DTC P0700) >> DTC P0638, P1551, P2100, P2101, P2119, or P2176 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2008 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.
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 valve that is free to move open or closed WITHOUT spring pressure
    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 each motor control circuit terminal A and B and ground.
    • If the test lamp illuminates, test the affected 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 each motor control circuit terminal A and B and B+.
    • If test lamp illuminates, test the affected motor control circuit for a short to ground. If the circuit tests normal, replace the ECM.
  5. Ignition ON, test for 3.5-4.7 volts between the Motor control circuit terminal B and ground.
    • If voltage is not within the specified range, test for an open or high resistance. If the circuit tests normal, replace the ECM.
  6. Ignition OFF, allow sufficient time for the ECM to completely power down. Connect a DMM between the motor control 2 terminal A circuit and ground.
    7. IMPORTANT: When measuring peak voltage, ensure that the DMM is on the proper voltage scale that the response time is set to 1 ms.
  7. Using the peak min max function, measure the voltage on the motor control 2 circuit as the ignition is turned ON. Voltage should be within 1 volt of ignition voltage.
    • If voltage is not within 1 volt of ignition voltage, test for an open or high resistance. If the circuit tests normal, replace the ECM.
  8. If all circuits test normal, replace the throttle body
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