GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2008 🢒 GMC W-Series Commercial W4 (W3500/W4500) 🢒 DTC 🢒 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

High Resistance

Open

Short to Voltage

Signal Performance

Motor Control 1

P1516, P2101, P2176

P1516, P2101, P2176

P1516, P2101, P2176

P1516, P2101, P2176

P1516, P2101, P2176

Motor Control 2

P1516, P2101, P2176

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. 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

P1516 and P2101

    • The ignition is ON.
    • The ignition voltage is more than 8 volts.
    • The system is not in the Battery Save mode.
    • The engine is running.
    • DTC P0068 is not set.
    • DTC P1516 and P2101 run continuously when the above conditions are met.

P2119

    • The ignition is ON.
    • The vehicle speed is 0 km/h (0 mph).
    • The ignition 1 voltage is more than 10 volts.
    • DTC P2119 runs once per ignition cycle when the above conditions are met for more than 1 second.

P2176

    • The ignition is ON.
    • DTCs P0120, P0122, P0123, P0220, P0222, P0223 are not set.
    • DTC P2176 runs once per key cycle.

Conditions for Setting the DTC

P1516

The indicated throttle position does not match the predicted throttle position for more than 0.5 second.

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 valve 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

P1516, P2101, and P2176

    • DTCs P1516, P2101, and P2176 are Type A DTCs.
    • The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.
    • The control module commands the TAC system to operate in the Reduced Engine Power mode.
    • A message center or an indicator displays Reduced Engine Power.
    • Under certain conditions, the control module commands the engine OFF.

P2119

    • DTC P2119 is a Type C DTC.
    • The control module stores the DTC information into memory when the diagnostic runs and fails.
    • The MIL will not illuminate.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
    • The driver information center, if equipped, may display a message.

Conditions for Clearing the MIL/DTC
    • DTCs P1516, P2101, and P2176 are Type A DTCs.
    • DTC P2119 is a Type C DTC.
    • The control module turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

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

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification
  1. Ignition ON, engine OFF, 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.
  2. 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 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.

    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.
    4. ⇒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.
    5. ⇒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+.
    6. ⇒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+.
    7. ⇒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.
    9. ⇒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.
    11. ⇒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.

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