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DTC P0234 or P0299

DTC P0234 or P0299

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 P0234

Engine Overboost

DTC P0299

Engine Underboost

Diagnostic Fault Information

Circuit Short to Ground High Resistance Open Short to Voltage Signal Performance
5 V Reference P0236 P0236, P0237 P0236 P0236 P0236
Boost Pressure Sensor Signal P0237 P0236, P0237 P0238 P0238 P0234, P0236, P0299
Low Reference - P0234, P0236, P0238 P0238 - -


Typical Scan Tool Data

Boost Pressure Sensor

Circuit Short to Ground Open Short to Voltage
Parameter Normal Range: BARO to 240 kPa (35 psi) Operating Conditions: Engine running under various operating conditions
5 V Reference 20-80 kPa (2.9-11.6 psi) 30-80 kPa (4.4-11.6 psi) 20-80 kPa (2.9-11.6 psi)
Boost Pressure Sensor Signal 0 kPa 276 kPa (40 psi) 276 kPa (40 psi)
Low Reference - 276 kPa (40 psi) -


Circuit Description

The boost pressure sensor is integrated with the intake air temperature (IAT) sensor. The boost pressure sensor measures the range of pressures between the turbocharger and the throttle body. Pressure in this portion of the induction system is affected by the following:


• Engine speed

• Throttle opening

• Turbocharger boost pressure

• Intake air temperature (IAT)

• Barometric pressure (BARO)

• Efficiency of the charge air cooler


The sensor provides a signal voltage to the engine control module (ECM), relative to the pressure changes, on the boost pressure sensor signal circuit. Under normal operation the greatest pressure that can exist in this portion of the induction system at ignition ON, engine OFF is equal to the BARO. When the vehicle is operated at wide-open throttle (WOT) the turbocharger can increase the pressure to near 240 kPa (35 psi). The least pressure that occurs is when the vehicle is idling or decelerating, and it is equal to the BARO.

Conditions for Running the DTCs


P0234

• The BARO is greater than 66 kPa (9.6 psi).

• The engine speed is between 2,000-3,720 RPM.

• The driver requested boost pressure level exceeds the level of the base boost pressure for more than 1 s.

• This DTC runs continuously within the enabling conditions.



P0299

• The BARO is greater than 66 kPa (9.6 psi).

• The engine speed is between 2,000-3,720 RPM.

• The driver requested boost pressure level exceeds the level of the base boost pressure for more than 6 s.

• This DTC runs continuously within the enabling conditions.


Conditions for Setting the DTC

P0234

The ECM detects that the actual boost pressure is 22-147 kPa (3.2-21.3 psi) greater than the desired boost pressure for greater than 1 s.

P0299

The ECM detects that the actual boost pressure is at least 27 kPa (3.9 psi) less than the desired boost pressure.

Action Taken When the DTC Sets

DTCs P0234 and P0299 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTCs P0234 and P0299 are Type B DTCs.

Diagnostic Aids

Use a solution of dish soap and water in a spray bottle to pinpoint any air leaks.

Reference Information

Schematic Reference

Engine Controls Schematics (3.0L (LF1)) Engine Controls Schematics (2.8L (LAU))

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

For equivalent regional tools, refer to Special Tools .

Circuit/System Verification


1. Ignition ON, observe the DTC information with a scan tool. Verify that DTC P0033, P0034, P0035, P0236, P0237, P0238, P0244, P0245, or P0246 is not set.

2. If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.

3. Verify the exhaust system is not restricted . Refer to Restricted Exhaust .

4. If DTC P0299 is set, verify the proper operation of the turbocharger bypass solenoid valve. Refer to Turbocharger Cleaning and Inspection .

5. Engine running, command the Turbocharger Bypass Solenoid Valve between Inactive and Active with a scan tool while observing the following control circuit status parameters:

• Turbocharger Bypass Solenoid Valve Control Circuit High Voltage Test Status

• Turbocharger Bypass Solenoid Valve Control Circuit Open Test Status

• Turbocharger Bypass Solenoid Valve Control Circuit Low Voltage Test Status

The parameters should alternate between OK and Not Run with each change in command.

6. Engine running, command the Turbocharger Wastegate Solenoid Valve to 20% with a scan tool while observing the following control circuit status parameters:

• Turbocharger Wastegate Solenoid Valve Control Circuit High Voltage Test Status

• Turbocharger Wastegate Solenoid Valve Control Circuit Open Test Status

• Turbocharger Wastegate Solenoid Valve Control Circuit Low Voltage Test Status

Each parameter should display OK.

7. Determine the current vehicle testing altitude. Observe the scan tool boost pressure sensor and BARO-sensor parameter Compare the parameters to each other and to the table Altitude versus barometric pressure The parameters should be within the range specified in the table and within 2 kPa of each other.

8. 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. Verify the integrity of the entire air induction system including all turbocharger components by inspecting for the following conditions:

• Any damaged components, including the turbocharger, the charge air cooler, and the turbo charger wastegate actuator solenoid valve

• Damage to the intake air pressure and temperature sensor

• Loose or improper installation

• An air flow restriction

• Any vacuum leaks

• Any pinholes or breaks in the vacuum hoses attached to the turbocharger wastegate solenoid valve

• Any restrictions in the vacuum hoses attached to the turbocharger wastegate solenoid valve

• Improper routing or connecting of the vacuum hoses on the turbocharger bypass solenoid valve , the bypass valve, and the turbocharger wastegate actuator solenoid valve

• Any type of air leak between the turbocharger and the throttle body, including the charge air cooler.

• Exhaust leaks

• If a condition is found, repair as necessary.

2. Ignition OFF, remove B65 intake air pressure and temperature sensor but leave the electrical connector connected.

3. Connect the J 24460-01 Cooling System Pressure Tester to the intake air pressure and temperature, boost pressure, sensor port with a suitable adapter. Engine running, observe the scan tool Boost Pressure Sensor parameter. Apply 6 psi to the B65 intake air pressure and temperature, boost pressure, sensor. Verify the scan tool Boost Pressure Sensor parameter responds to the applied pressure.

4. If the scan tool Boost Pressure Sensor parameter does not increase with the applied pressure, replace the B65 intake air pressure and temperature sensor.

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

6. If restricted, repair or replace as necessary.

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


Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.


• Turbocharger Pressure Sensor Replacement for intake air pressure and temperature sensor replacement.

• Turbocharger Removal

• Turbocharger Disassemble

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