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 P2072: Throttle Actuator Control (TAC) System Ice Blockage

### 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 DTCs

• | The ignition is ON.

• | The DTC runs continuously once the above condition is met.

### Conditions for Setting the DTC

#### DTC P2072

The ECM detects the throttle blade is stuck open or stuck closed for 1 second.

### Action Taken When the DTC Sets

DTC P2072 is a Type A DTC.

### Conditions for Clearing the DTC

DTC P2072 is a Type A DTC.

### Diagnostic Aids

Inspect for a condition in which the throttle valve may have been held open. For example, ice may have formed in the throttle bore causing the throttle valve not to close.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

• | Engine Control Module Connector End Views

• | Engine Controls 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

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Scan Tool Output Controls

#### Special Tools Required

J 34730-405 Injector Test Lamp

### Circuit/System Verification

1. Ignition ON, observe the scan tool DTC information parameter. Verify DTCs P0121, P0122, P0123, P0221, P0222, or P0223 are not set.

⇒ | If any of the DTCs are set, refer to DTC P0121, P0122, P0123, P0221, P0222, or P0223 for further diagnosis.

2. Verify TP sensor 1 voltage is between 0.4-0.9 volt, and TP sensor 2 voltage is between 4.1-4.7 volts.

⇒ | If either TP sensor voltage is not within the specified range, refer to DTC P0121, P0122, P0123, P0221, P0222, or P0223 for further diagnosis.

3. Rapidly depress the accelerator pedal from the rest position to the wide open throttle position (WOT) and release pedal. Repeat the procedure several times. DTC P2072 should not set.

⇒ | If any of the DTCs P0121, P0122, P0123, P0221, P0222, or P0223 set while performing this procedure, refer to DTC P0121, P0122, P0123, P0221, P0222, or P0223 for further diagnosis.

4. Slowly depress the accelerator pedal to WOT and then slowly return the pedal to closed throttle. Repeat the procedure several times. DTC P2072 should not set.

⇒ | If any of the DTCs P0121, P0122, P0123, P0221, P0222, or P0223 set while performing this procedure, refer to DTC P0121, P0122, P0123, P0221, P0222, or P0223 for further diagnosis.

5. 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 Data List.

### Circuit/System Testing

1. Inspect the throttle body for the following conditions:

• | A throttle blade that is not in the rest position

• | A throttle valve that is binding open or closed

• | A throttle valve that opens or closes without spring pressure

⇒ | If a condition is found, replace the throttle body.

Important: Disconnecting the throttle body harness connector causes additional DTCs to set.

2. Ignition OFF, disconnect the harness connector at the throttle body.
3. Install fused jumper wires between the throttle body and harness connector of the following circuits:

• | Low reference circuit

• | 5-volt reference circuit

• | TP sensor 1 or TP sensor 2 signal circuit

4. Ignition ON, test for less than 0.5 volts on the motor control 1 and motor control 2 circuits.

⇒ | If greater than the specified value, test the appropriate motor control circuit for a short to voltage. If the circuit tests normal, replace the ECM.

Important: The scan tool TAC motor command is disabled, if multiple TP sensor or TAC circuit DTCs are set.

5. Ignition OFF, command the TAC motor with the scan tool, while measuring the voltage of the TAC motor control 1 circuit and TAC motor control 2 circuit at the harness connector.

⇒ | If the voltage changes between 0.0 volts to greater than 10.5 volts on both circuits, replace the throttle body.

⇒ | If the voltage changes between 0.0 volts to less than 10.5 volts on either circuit, test for an open or a short to ground in the appropriate TAC motor control circuit.

⇒ | If the circuits test normal, replace the ECM.

### 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