GM Service Manual Online
For 1990-2009 cars only

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 Descriptor

DTC P2102: Throttle Actuator Control Motor Circuit Low Voltage

DTC P2103: Throttle Actuator Control Motor Circuit High Voltage

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

TAC Motor Control High

P2102

P2102, P2119*

P2103

P2102

TAC Motor Control Low

P2103

P2102, P2119*

--

--

*P2119 set when resistance in the circuit was less than 15 ohms

Circuit/System Description

The throttle valve in the throttle body utilizes a throttle return spring to assist in positioning the throttle valve at a resting or default position. The powertrain control module (PCM) uses driver input from the accelerator pedal position (APP) sensor in order to calculate the desired throttle position. The PCM sends the desired throttle position or target value to the throttle actuator control (TAC) module. The TAC module achieves the desired throttle position by commanding the throttle control motor to position the throttle valve at the target value. The TAC module then compares the throttle position (TP) sensor 1 value to the target value. If necessary, the throttle control motor is moved slightly in order to obtain the exact target value position.

Conditions for Running the DTC

    • The power supply to the TAC motor is more than 8 volts.
    • The DTCs run continuously once the above condition has been met.

Conditions for Setting the DTC

P2102

When the duty cycle of the open command for the TAC motor is more than 80 percent, the TAC motor current is less than 0.5 amp.

P2103

    • The TAC motor current is more than 7 amps for 600 milliseconds.
        OR
    • The TAC motor current is more than 10 amps for 100 milliseconds.

Action Taken When the DTC Sets

    • DTC P2102 and P2103 are Type A DTCs.
    • The PCM enters the Fail-Safe function operating in the Reduced Engine Power Mode. The throttle valve return spring will close the throttle valve to the idle position with the TP sensor 1 angle defaulted to 19 percent.

Conditions for Clearing the DTC

DTC P2102 and P2103 are Type A DTCs.

Diagnostic Aids

    •  TAC Motor Current is displayed on the scan tool, but the displayed value freezes when the MIL illuminates and the DTC sets.
    • DTC P2103 can set from a momentary current surge that occurs when the TAC system ignition 1 voltage supply to the PCM is interrupted. Diagnose this failure using the procedure in DTC P2118. Refer to DTC P2118.
    • Engine acceleration will be compromised and AT downshifts delayed when operating in the Fail-safe mode.

Reference Information

Schematic Reference

Engine Controls Schematics

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

  1. Ignition ON, observe the DTC information with a scan tool. Verify DTC P2118 is not set.
  2. If DTC P2118 is set, refer to DTC P2118.
  3. Ignition ON, rapidly depress the accelerator pedal from the rest position to the wide open throttle position (WOT) and release pedal. Repeat the procedure several times. DTCs P2102 or P2103 should not set.
  4. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Circuit/System Testing

    Important: 

       • The TAC system DTCs must be cleared before testing for voltage. The PCM will not provide voltage to the TAC motor circuits when a TAC or TP sensor DTC is set.
       • The engine cannot be running when testing for voltage. If the engine is started, a TAC system DTC will set and the PCM will not provide voltage to the TAC motor circuits.
       • Do not disconnect the TAC module harness connector unless instructed to do so. A TP sensor DTC will set when the ignition is turned ON.

  1. Ignition OFF, disconnect the harness connector at the TAC module.
  2. Important: With the TAC module disconnected, a TP sensor DTC will set and the PCM will not provide voltage to the TAC motor circuits.

  3. Ignition ON, test for 0 volts between the TAC motor control circuit terminal terminals and ground.
  4. If greater than the specified range, test the TAC motor control circuit for a short voltage. If the circuit tests normal, replace the PCM.
  5. Ignition OFF, connect the following TP sensor circuits together with four fused jumper wires.
  6. • TP sensor 1 signal circuit terminal 6
    • TP sensor 2 signal circuit terminal 4
    • TP sensor 5-volt reference circuit terminal 5
    • TP sensor ground circuit terminal 3
  7. Ignition ON, test for B+ between the TAC motor control circuit terminals listed below and ground.
  8. • TAC motor control low circuit terminal 1
    • TAC motor control high circuit terminal 2
    If less than the specified range, test the TAC motor control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the PCM.
  9. If all circuits test normal, test or replace the throttle body assembly.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

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