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 Descriptor

DTC P0068 00: Throttle Body Air Flow Performance
DTC P0121 00: Throttle Position Sensor 1 Performance
DTC P0221 00: Throttle Position Sensor 2 Performance

### Circuit/System Description

The engine control module (ECM) uses the following information to calculate an expected airflow rate:

• | The throttle position

• | The barometric pressure (BARO)

• | The intake air temperature (IAT)

• | The engine speed

• | The manifold absolute pressure (MAP)

### Conditions for Running the DTC

• | DTCs P000A 00, P000B 00, P0016 00, P0017 00, P0111 00, P0112 00, P0113 00, P0114 00, P0116 00, P0117 00, P0118 00, P0119 00, P0122 00, P0123 00, P0222 00, P0223 00, P0121 00, P0221 00, P0340 00, P0341 00, P0365 00, P0366 00, P0458 00, P0459 00, P0642 00, P0643 00, P0652 00, P0653 00, P065B 00 are not set

• | The engine is running.

• | DTCs P0068 00, P0642 00, P0643 00 are not set.

### Conditions for Setting the DTC

The ECM detects that the actual airflow rate is more than the calculated airflow.

### Action Taken When the DTC Sets

• | DTCs P0068 00 is a Type B DTC.

• | DTCs P0121 00 and P0221 00 are Type A DTCs.

• | 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.

### Conditions for Clearing the DTC

• | DTCs P0068 00 is a Type B DTC.

• | DTCs P0121 00 and P0221 00 are Type A DTCs.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component 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

Control Module References for scan tool information

### Circuit/System Verification

1. Verify that DTCs P0122 00, P0123 00, P0222 00, or P0223 00 are not set. Refer to DTC P0122, P0123, P0222, or P0223.
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

1. Inspect for the following conditions:

• | Vacuum hoses for splits, kinks, and proper connections.

• | Inspect thoroughly for any type of leak or restriction.

• | Air leaks at throttle body mounting area and intake manifold sealing surfaces.

2. Take a snapshot of the engine data list while performing the actions listed below. The MAP sensor kPa should increase as the engine speed is increased and decreased as the throttle is returned to idle.

• | Idle the engine.

• | Increase the engine speed slowly to 3000 RPM, then back to idle.

• | Exit from the snapshot and review the data.

• | Observe the MAP parameter frame by frame with a scan tool. The MAP should change smoothly and gradually as the engine speed is increased and is returned to idle.

⇒ | If the MAP does not change smoothly and gradually as the engine speed is increased and is returned to idle refer to DTC P0106, P0107, or P0108.

3. Inspect the throttle body for the following conditions:

• | Loose or damaged throttle blade

• | Broken throttle shaft

• | Any throttle body damage

⇒ | If any of these conditions exist, replace the throttle body assembly.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Throttle Body Assembly Replacement

• | Engine Control Module Replacement for ECM replacement, setup, and programming