For 1990-2009 cars

### 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 P2105: Throttle Actuator Control (TAC) System - Forced Engine Shutdown

### Circuit/System Description

The engine control module (ECM) controls the throttle valve by applying a varying voltage to the control circuits of the throttle actuator control (TAC) motor. The ECM monitors the duty cycle that is required to actuate the throttle valve. The ECM monitors the throttle position (TP) sensors 1 and 2 to determine the actual throttle valve position.

### Conditions for Running the DTC

• | The ECM power down process in the last drive cycle was completely finished.

• | DTC P2105 runs continuously once the above condition is met for greater than 5 seconds.

### Conditions for Setting the DTC

• | The ECM detects an incorrect voltage level at the ignition voltage supply circuits.

| OR

• | The ECM detects an internal communication error.

• | The condition exists, then a 5 second delay for MIL ON.

### Action Taken When the DTC Sets

DTC P2105 is a Type A DTC.

### Conditions for Clearing the DTC

DTC P2105 is a Type A DTC.

### Diagnostic Aids

• | If DTC P2105 sets, the engine will stall and not restart until the ignition is cycled OFF and then ON.

• | Additional DTCs set when P2105 sets.

• | The ignition key will not be able to be removed from the ignition switch until another ignition cycle occurs.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Engine Control Module 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. Start the engine. Rapidly move the accelerator pedal from the rest position, to wide open throttle position, back to the rest position. Repeat the procedure a few times. DTC P2105 should not set.
2. 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

1. Ignition OFF, remove the fuse that supplies voltage to terminal X2-5 of the ECM. Verify the fuse is OK.

Note: This DTC will only set if the fuse is open and the circuits are not grounded. The ignition voltage circuits must be tested thoroughly for an intermittent short to ground.

⇒ | If the fuse is open, test the ignition voltage circuit between the open fuse and the ECM for an intermittent short to ground.

2. Install the fuse.
3. Disconnect the harness connectors of the ECM.
4. Ignition ON, load test for B+ on the ignition circuit terminal X2-5 of the ECM connector.

⇒ | If less than B+, repair the ignition circuit for an open/high resistance.

5. If all circuits/connections test OK, replace the ECM.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for engine control module replacement, setup, and programming