GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2008 🢒 Terraza Ext. 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC P1516, P2101, P2119, or P2176

Diagnostic Instructions
    •  Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    •  Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P1516: Throttle Actuator Control (TAC) Module Throttle Actuator Position Performance

DTC P2101: Throttle Actuator Position Performance

DTC P2119: Throttle Closed Position Performance

DTC P2176: Minimum Throttle Position Not Learned

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

TAC Motor Control 1

P1516, P2101, P2176

P1516, P2101, P2176

P1516, P2101, P2176

P1516, P2101, P2176

TAC Motor Control 2

P1516, P2101, P2176

P1516, P2101, P2176

P1516, P2101, P2176

P1516, P2101, P2176

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 through the motor control 1 circuit and the motor control 2.

Two processors are used to monitor the TAC system data. Both processors are located within the ECM. Both processors monitor and share data to verify that the indicated throttle position is correct.

Conditions for Running the DTC

P1516

    • DTC P0068 or P0121 is not set.
    • The ignition is in the Run or Crank position.
    • The ignition voltage is greater than 6.5 volts.
    • The engine is running, or the system is not in the Battery Save mode if the engine is not running.
    • The DTC runs continuously when the above conditions are met.

P2101

    • DTC P0068 or P0121 is not set.
    • The ignition is in the Run or Crank position.
    • The system voltage is greater than 11 volts.
    • The engine is running or the system is not in Battery Saver mode if the engine is not running.
    • The DTC runs continuously when the above conditions are met.

P2119

    • The ignition is in the Unlock/Accessory, Run, or Crank position.
    • The ignition voltage is greater than 5.23 volts.
    • The system is in the Battery Save mode.
    • The DTC runs continuously when the above conditions are met.

P2176

    • The ignition is in the Run or Crank position.
    • DTC P0120, P0122, P0123, P0220, P0222, P0223, or P2135 is not set.
    • The system is in the minimum throttle position (TP) learn state.
    • The throttle is stable for greater than 40 milliseconds.
    • The DTC runs continuously when the above conditions are met.

Conditions for Setting the DTC

P1516

    •  The indicated throttle position does not match the predicted throttle position for greater than 0.5 second.
        OR
    • The ECM detects a current draw of greater than 9 amps on the motor circuits for greater than 0.18 second.

P2101

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

P2119

The ECM detects that the throttle is unable to return to the default position after it is de-energized for greater than 0.5 second.

P2176

The ECM detects that the minimum throttle position was not learned for greater than 1.8 seconds.

Action Taken When the DTC Sets
    • DTCs P1516, P2101, and P2176 are Type A DTCs.
    • DTC P2119 is a Type C DTC.
    • The ECM commands the TAC system to operate in the Reduced Engine Power mode.

Conditions for Clearing the MIL/DTC
    • DTCs P1516, P2101, and P2176 are Type A DTCs.
    • DTC P2119 is a Type C DTC.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Throttle Actuator Control (TAC) System Description

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

With the ignition ON, use a scan tool to observe the 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.

⇒Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

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:
    2. • 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 throttle body.
  2. Ignition OFF, disconnect the harness connector at the throttle body.
  3. Ignition ON, verify that a test lamp does not stay illuminated between the motor control 1 circuit and ground.
    4. ⇒If test lamp stays illuminated, 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 stay illuminated between motor control 2 circuit and ground.
    5. ⇒If test lamp stays illuminated, test the affected 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 the motor control 1 circuit and B+.
    6. ⇒If test lamp illuminates, test the affected 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 the motor control 2 circuit and B+.
    7. ⇒If 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 and ground.

    8. Important: When measuring peak voltage, ensure that the DMM is on the proper voltage scale and the response time is set to 1 ms.

  8. Using the peak min max function measure for ignition voltage on the motor control 1 circuit as the ignition is turned ON. The voltage should be within 1 volt of the ignition voltage.
    9. ⇒If not the specified value, test for an open or high resistance. If the circuit tests normal, replace the ECM.
  9. Ignition OFF, allow sufficient time for the ECM to completely power down. Connect a DMM between the motor control 2 circuit and ground.
  10. 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.
    11. ⇒If not the specified value, test for an open or high resistance. If the circuit tests normal, replace the ECM.
  11. If all circuits test normal, replace the throttle body.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Throttle Body Assembly Replacement
    •  Control Module References for ECM replacement, setup, and programming