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 provide an overview of each diagnostic category.

### DTC Descriptors

DTC P2104: Throttle Actuator Control (TAC) System - Forced Engine Idle
DTC P2105: Throttle Actuator Control (TAC) System - Forced Engine Shutdown
DTC P2106: Throttle Control System Performance - Throttle Limitation Active
DTC P2110: Throttle Actuator Control (TAC) System - Forced Limited Engine Speed

### Circuit/System Description

DTC P2104, P2105, P2106, and P2110 indicate that a throttle actuator control (TAC) DTC is set that causes the engine control module (ECM) to command one of the following Reduced Power modes:

• | Forced engine idle

• | Forced engine shutdown

• | Throttle limitation

• | Limited engine speed

### Conditions for Running the DTC

The ignition is ON or the engine is operating.

### Conditions for Setting the DTC

A failure with the TAC system is present.

### Action Taken When the DTC Sets

#### P2104, P2106, and P2110

• | DTC P2104, P2106, and P2110 are Type A DTCs.

• | The ECM commands the TAC system to operate in a Reduced Engine Power mode.

• | The ECM commands the reduced engine power indicator ON.

#### P2105

• | DTC P2105 is a Type B DTC.

• | Engine operation will be disabled.

### Conditions for Clearing the DTC

DTC P2104, P2106, and P2110 are Type A DTCs. DTC P2105 is a Type B DTC.

### Reference Information

#### Description and Operation

Throttle Actuator Control (TAC) System Description

### Circuit/System Verification

Important:

• | A low battery condition while cranking the engine may cause DTC P2106 to set. Refer to Symptoms - Engine Electrical .

• | In extreme cold weather conditions ice may form in the vacuum source to the MAP sensor and may set a DTC. Inspect the MAP sensor and the vacuum source for ice, moisture, or other restrictions.

1. Ignition ON, observe the MAP sensor data parameter with a scan tool. Start the engine, verify the MAP sensor data parameter changes.

⇒ | If the MAP data parameter does not change, refer to DTC P0107 or P0108 for further diagnosis.

2. Verify that no vacuum leak exists.

⇒ | If a vacuum does exist, repair as necessary.

3. DTCs P2104, P2105, P2106, and P2110 are informational DTCs. Correct the throttle actuator control (TAC) system DTCs that are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .
4. If the vehicle passes the Circuit/System Verification test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records List.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for ECM replacement, setup, and programming