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Home >> Chevrolet >> 2009 >> Cobalt L4-2.0L Turbo >> Repair and Diagnosis >> A L L Diagnostic Trouble Codes ( DTC ) >> Testing and Inspection >> P Code Charts >> P2176

P2176




DTC P0638, P1551, P2100, P2101, P2119, or P2176

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview)provides an overview of each diagnostic category.

DTC Descriptors
DTC P0638
- Throttle Actuator Control (TAC) Command Performance

DTC P1551
- Throttle Valve Rest Position Not Reached During Learn

DTC P2100
- Throttle Actuator Control (TAC) Motor Control Circuit

DTC P2101
- Control Module Throttle Actuator Position Performance

DTC P2119
- Throttle Closed Position Performance

DTC P2176
- Minimum Throttle Position Not Learned

Diagnostic Fault Information





Circuit/System Description

The engine control module (ECM) is the control center for the throttle actuator control (TAC) system. The ECM determines the drivers intent and then calculates the appropriate throttle response. The ECM achieves throttle positioning by providing a pulse width modulated voltage to the TAC motor. The TAC system uses the following circuits:

* Motor control 1
* Motor control 2

Two processors are also used to monitor the TAC system data. Both processors are located within the ECM. Both processors monitor each other's data to verify that the indicated throttle position is correct.

Conditions for Running the DTC

P0638, P2100, P2101
* The ignition is ON.
* The ignition voltage is more than 7 volts.
* The system is not in the Battery Save mode.
* DTC P0638, P2100, P2101 run continuously when the above conditions are met.

P1551 and P2119
* The ignition is ON.
* The ignition voltage is more than 7 volts.
* The system is in the Battery Save mode.
* DTCs P1551 and P2119 run once when the above conditions are met.

P2176
* The ignition is ON.
* The ignition voltage is more than 7 volts.
* The system is not in the Battery Save mode.
* The engine is running.
* DTCs P0121, P0122, P0123, P0221, P0222, P0223 are not set.
* DTC P2176 runs continuously when the above conditions are met.

Conditions for Setting the DTC

P0638

The motor control pulse width is more than 80 percent for more than 4 seconds.

P1551, P2100, and P2101

The indicated throttle position does not match the predicted throttle position for more than 0.3 second.

P2119

The ECM determines that the throttle blade did not return to the rest position within 720 milliseconds.

P2176

The difference between the predicted and the actual throttle position is more than a calibrated amount for more than 1.5 seconds.

Action Taken When the DTC Sets

* DTCs P0638, P2100, P2101, and P2176 are Type A DTCs.
* DTCs P1551 and P2119 are Type C DTCs.

Conditions for Clearing the DTC

* DTCs P0638, P2100, P2101, and P2176 are Type A DTCs.
* DTCs P1551 and P2119 are Type C DTCs.

Reference Information
Schematic Reference

Engine Controls Schematics (Electrical Diagrams)
Connector End View Reference

Component Connector End Views (Connector Views)
Description and Operation

Throttle Actuator Control (TAC) System Description (Throttle Actuator Control (TAC) System Description)
Electrical Information Reference

* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Diagnostic Trouble Code Descriptions)
Scan Tool Reference

Control Module References (Programming and Relearning)for scan tool information

Circuit/System Verification

1. Ignition ON, use a scan tool to observe the throttle position (TP) sensor 1 indicated position. Throttle position should increase as pedal is applied and decrease as pedal is released. When no accelerator pedal activity is detected, the throttle position will return to the spring loaded default position.

Note: A low voltage condition may set this DTC.

2. Review the Freeze Fame/Failure Records and ensure sufficient ignition voltage was present when the DTC was set.

• If voltage was low, verify with the owner that the battery was not discharged. If the battery has not been discharged, refer to Power Mode Mismatch (Power Mode Mismatch).

Circuit/System Testing

Warning

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

Note: 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.

Note: 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

Repair Instructions

Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.

* Throttle Body Assembly Replacement (Removal and Replacement)
* Control Module References (Programming and Relearning)for ECM replacement, setup, and programming

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