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	P0107, P0193, P0236, P0642	P0236, P0237	P0107, P0236	P0036, P0193, P0236, P050A, P0606, P0643	P0236
Intake air pressure signal	P0237	P0236, P0237	P0238	P0238	P0234, P0236, P0299
Low Reference	-	P0234, P0236, P0238	P0098, P0099, P0238	-	-

Typical Scan Tool Data

Boost Pressure Sensor

Circuit	Short to Ground	Open	Short to Voltage
Parameter Normal Range: BARO to 240 kPa Operating Conditions: Engine Running at various operating conditions
5 V Reference	20-80 kPa	30-80 kPa	20-80 kPa
Boost Pressure Sensor	0 kPa	276 kPa	276 kPa
Low Reference	-	276 kPa	-

Circuit Description

The intake air pressure sensor is integrated with the intake air temperature (IAT) sensor 2. The intake air pressure sensor measures the range of pressures between the turbocharger and the throttle body. The sensor used on this engine is a three atmosphere sensor. Pressure in this portion of the induction system is affected by engine speed, throttle opening, turbocharger boost pressure, intake air temperature (IAT), barometric pressure (BARO), and the 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 intake air pressure 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. 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

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DTC P0010, P0013, P0014, P0016, P0017, P0018, P0033, P0034, P0035, P00C0, P0101, P0102, P0103, P0106, P0107, P0108, P0111, P0112, P0113, P0114, P0121, P0122, P0123, P0128, P0222, P0223, P0234, P0236, P0237, P0238, P0243, P0245, P0246, P0299, P0606, P16F3, P2227, P2228, P2229, P2230 or P2261 is not set.

•	The driver requested boost pressure level exceeds the level of the base boost pressure.

•	The engine speed is between 1600-6000 RPM.

•	The desired boost pressure is between 140-300 kPa.

•	The Barometric Pressure (BARO) is between 60-120 kPa.

•	The Engine Coolant Temperature (ECT) is between -40-120°C (-40-248°F).

•	The Intake Air Temperature (IAT) is between -40-80°C (-40-176°F)

•	The turbocharger wastegate is not under output device control.

•	The turbocharger bypass valve is not under output device control.

•	The DTCs run continuously when the above conditions have been met.

Conditions for Setting the DTC

P0234

The ECM detects that the actual boost pressure is greater than the desired boost pressure by a calibrated amount for greater than 1.5 s.

P0299

The ECM detects that the actual boost pressure is less than the desired boost pressure by a calibrated amount for greater than 1.5 s.

Action Taken When the DTC Sets

•	DTCs P0234 and P0299 are Type B DTCs.

•	An indicator will illuminate.

•	The ECM will disable boost control and limit the system to mechanical boost only, resulting in a substantial decrease in engine power.

Conditions for Clearing the MIL/DTC

DTCs P0234 and P0299 are Type B DTCs.

Diagnostic Aids

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The charge air cooler is connected to the turbocharger and to the throttle body by flexible duct work that requires the use of special high torque fastening clamps. These clamps cannot be substituted. In order to prevent any type of air leak when servicing the ductwork, the tightening specifications and proper positioning of the clamps is critical and must be strictly adhered to.

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

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

Circuit/System Verification

1.	Ignition ON, command the Turbocharger Bypass Solenoid Valve ON and OFF with a scan tool. A click should be heard and felt in response to the commands.

2.	Command the Turbocharger Wastegate Solenoid between 20-90 % with a scan tool. A series of clicks should be heard and felt in response to the commands.

3.	Ignition ON, observe the scan tool MAP Sensor, Boost Pressure Sensor and BARO Sensor parameters. Compare the parameters to the Altitude Versus Barometric Pressure table. The parameters should be within the specified range displayed in the table for the specific altitude.

4.	Compare the scan tool MAP Sensor parameter to the Boost Pressure Sensor parameter during a WOT acceleration at the time of the 1-2 shift. The values read off should be between 20 kPa.

5.	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 and exhaust systems, including all turbocharger components, by inspecting for the following conditions:

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Damaged components

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Hairline fractures of the boost pressure sensor housing

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Hairline fractures of the MAP sensor housing

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Loose or improper installation

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An air flow restriction

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Vacuum line restrictions

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Vacuum leaks

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An air leak between the turbocharger and the throttle body, including the charge air cooler assembly.

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Verify that an exhaust leak does not exist, including the mating surface area between the turbocharger and the exhaust manifold.

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Verify that restrictions do not exist in the exhaust system. Refer to Restricted Exhaust.

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If a condition is found, repair or replace the affected component as necessary.

2.	If all inspections are normal, test or replace the B65 intake air pressure and temperature sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

•	Intake Air Pressure and Temperature Sensor Replacement

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