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 P0234: Engine Overboost
DTC P0299: Engine Underboost

### Circuit/System Description

The turbocharger pressure sensor responds to pressure changes in the intake manifold. The pressure changes occur based on the engine load, and turbocharger boost. The engine control module (ECM) supplies 5 volts to the turbocharger pressure sensor on the 5-volt reference circuit. The ECM provides a ground on the low reference circuit. The turbocharger pressure sensor provides a signal to the ECM on the signal circuit which is relative to the pressure changes in the manifold.

### Condition for Running the DTC

• | The engine is running.

• | The DTCs run continuously when the above conditions are met.

### Conditions for Setting the DTC

#### P0234

The actual turbocharger boost pressure is greater than the desired range for greater than 6 seconds.

#### P0299

The actual turbocharger boost pressure is less than the desired range for greater than 6 seconds.

### Action Taken When the DTC Sets

DTCs P0234 and P0299 are Type B DTCs.

### Conditions for Clearing the DTC

DTCs P0234 and P0299 are Type B DTCs.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

Turbocharger 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

#### Special Tools

J 24460-01 Cooling System Pressure Tester

### Circuit/System Verification

1. Ignition ON, compare the scan tool boost pressure sensor parameter to the manifold absolute pressure (MAP) sensor parameter. Both parameters should be within 5 kPa.

⇒ | If not within the specified range, refer to DTC P0069 for further diagnosis.

2. Observe the DTC information with a scan tool. Verify that DTC P0045 is not set.

⇒ | If DTC P0045 is are set, refer to DTC P0045 for further diagnosis.

3. Engine running, increase the engine speed to 2,000 RPM. Command the turbocharger boost solenoid valve from 0-100 percent and back to 0 percent with a scan tool. Verify the scan tool boost pressure sensor parameter increases and decreases with the scan tool commands.
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

1. Inspect the intake, and the exhaust systems, for the following:

• | Leaks or restrictions

• | Damaged or missing components

• | Aftermarket components

⇒ | If a condition is found, repair as necessary.

2. Ignition OFF, remove the turbocharger boost pressure sensor from the intake manifold.
3. Connect the J 24460-01 Cooling System Pressure Tester to the turbocharger boost pressure port with a suitable adapter. Engine running, observe the scan tool boost pressure parameter. Apply 6 psi to the boost pressure sensor. Verify the scan tool boost pressure sensor parameter responds to the applied pressure.

⇒ | If the scan tool boost pressure sensor parameter does not increase with the applied pressure, replace the turbocharger boost sensor.

4. Inspect the turbocharger oil supply lines for a restriction.

⇒ | If restricted, repair or replace as necessary.

5. If all other components test normal, test or replace the turbocharger.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Intake Air Pressure and Temperature Sensor Replacement

• | Turbocharger Replacement

• | Control Module References for ECM replacement, setup, and programming