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Home >> Chevrolet >> 2017 >> Spark LT, Automatic CVT Trans >> Repair and Diagnosis >> External Pages >> Different car >> Section 81 (Engine Controls And Fuel - 1.6L (LWC) - DTC P0243 To DTC P2635 And Diagnostic Information And Procedures) >> Diagnostic Information and Procedures >> DTC P1516, P2101, P2119, or P2176 >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2019 Buick Cascada, 2018 Buick Cascada, and 2017 Buick Cascada. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF.
    2. WARNING:

    Turn OFF the ignition before inserting fingers into the throttle bore. Unexpected movement of the throttle blade could cause personal injury.

  2. Verify the conditions listed below do not exist with the Q38 Throttle Body:
      NOTE:
      • The rest position is defined as the actual Throttle Position percentage when the ignition is OFF or with the ignition ON for greater than 30 seconds.
      • When the ignition is OFF, spring tension should hold the throttle plate in the rest position. You should be able to open the throttle plate to wide open throttle (WOT) or push the throttle plate to the fully closed position. In each case, the throttle plate should return to the rest position without assistance.
    • A throttle blade that is not in the rest position
    • A throttle blade 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 Q38 Throttle Body.

    • Go to next step: If a condition is not found 
    3. NOTE:

    Disconnecting the throttle body harness connector may cause additional DTCs to set.

  3. Disconnect the harness connector at the Q38 Throttle Body, ignition ON.
    4. NOTE:

    The test lamp may illuminate briefly when the ignition switch is turned on, but should not remain illuminated.

  4. Verify that a test lamp does Not illuminate continuously between each motor control circuit listed below and ground.
    • TAC Motor Control Open circuit terminal 1
    • TAC Motor Control Closed circuit terminal 2
    • If the test lamp is always ON 
    1. Ignition OFF, remove the test lamp. Disconnect the harness connector X2 at the K20 Engine Control Module, ignition ON
    2. Test for less than 1 V between the motor control circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K20 Engine Control Module.
    • Go to next step: If the test lamp is always OFF 
  5. Verify that a test lamp does not illuminate between each motor control circuit listed below and B+.
    • TAC Motor Control Open circuit terminal 1
    • TAC Motor Control Closed circuit terminal 2
    • If the test lamp illuminates 
    1. Ignition OFF, remove the test lamp. Disconnect the harness connector X2 at the K20 Engine Control Module.
    2. Test for infinite resistance between the control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the K20 Engine Control Module.
    • Go to next step: If the test lamp does not illuminate 
  6. Ignition OFF, remove the test lamp. Set the DMM to the 40 V scale, select the Min/Max Recording Mode, and set the Peak Min/Max response time to 1 ms.
    7. NOTE:
    • The test lamp must be connected to circuit before turning ignition on or incorrect diagnosis may occur.
    • The ignition must be OFF and the ECM completely powered down before testing each circuit or a lower voltage will be recorded. It may take up to 2 min for all vehicle systems to power down.
    • The DMM Min/Max Recording Mode and the response time of 1 ms must be reset after testing each circuit or a lower voltage will be recorded.
  7. Verify the Max voltage is within 3 V of B+ while using DMM Min/Max Recording Mode function on each control circuit listed below as the ignition is turned ON.
    • TAC Motor Control Open circuit terminal 1
    • TAC Motor Control Closed circuit terminal 2
    • If not within 3 V of B+ 
    1. Ignition OFF, disconnect the harness connector X2 at the K20 Engine Control Module.
    2. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K20 Engine Control Module.
    • Go to next step: If within 3 V of B+ 
  8. Replace the Q38 Throttle Body.
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