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Home >> Buick >> 2013 >> Verano L4-2.0L Turbo >> Repair and Diagnosis >> A L L Diagnostic Trouble Codes ( DTC ) >> Testing and Inspection >> P Code Charts >> P0234

P0234




DTC P0234 or P0299

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.

* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC P0234
- Engine Overboost

DTC P0299
- Engine Underboost

Diagnostic Fault Information






Typical Scan Tool Data






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 (34.8 psi). The least pressure that occurs is when the vehicle is idling or decelerating, and it is equal to BARO.

Conditions for Running the DTCs

* DTC P0010, P0011, 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, P2101, 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 1,600-6,000 RPM.

* The desired boost pressure is between 140-300 kPa (20.3-43.5 psi)

* The Barometric Pressure (BARO) is between 60-120 kPa (8.7-17.4 psi).

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

* The Intake Air Temperature (IAT) is between -40 to +80°C (-40 to +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

Note: While DTC P0234 or P0299 is set, the system software will limit the air flow resulting in a no boost condition.

* 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

* 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 [1][2]Electrical Diagrams

Connector End View Reference

Component Connector End Views Outside Rearview Mirror - Driver

Description and Operation

Turbocharger System Description Description and Operation

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References Control Module References for scan tool information

Special Tools

J-23738-A - Mityvac

Circuit/System Verification

1. Ignition ON, observe the DTC information with a scan tool. Verify DTC P0106, P0107, P0108, P0236, P0237, P0238, P0243, P0245, P0246, P2227, P2228, P2229, or P2230 is not set.

• If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.

2. Ignition ON, command the Turbocharger Bypass Solenoid between Active and Inactive with a scan tool. A click should be heard and felt from the solenoid.

3. Command the Turbocharger Wastegate Solenoid between 15-100 % with a scan tool. A series of clicks should be heard and felt from the solenoid and should increase in frequency as the duty cycle percentage is increased.

4. Observe the scan tool MAP Sensor, Boost Pressure Sensor and BARO Sensor parameters. Compare the parameters to the Altitude Versus Barometric Pressure Specifications table. The parameters should be within 3 kPa (0.4 psi) and should be within the range specified in the table for the current altitude.

5. 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 readings should be within 20 kPa (2.9 psi).

6. 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 system including all turbocharger components by inspecting for the conditions listed below:

* The air intake duct system for loose clamps, cracks or other damage

* The air intake duct system for being collapsed or restricted

* Restricted air filter

* An air flow restriction

* Any type of air leak between the turbocharger and the throttle body, including the charge air cooler assembly

* Splits, kinks or improper connections at the vacuum hoses

* Any vacuum leak

* Restricted, leaking or incorrect routing of vacuum or pressure hoses going to the components listed below:

- Q42 turbocharger wastegate solenoid valve

- Q40 turbocharger bypass solenoid valve

- Intake manifold and turbocharger bypass valve vacuum tank

- Turbocharger

- Turbocharger wastegate actuator

- Turbocharger bypass valve

* Missing, restricted or leaking exhaust components. Refer to Symptoms - Engine Exhaust Symptoms - Engine Exhaust.

* Exhaust leak between the turbocharger and the exhaust manifold

* Restricted or leaking turbocharger oil supply line

* Loose or incorrect installation of any components

• If a condition exists, repair as necessary.

2. Ignition OFF, disconnect the vacuum supply hose from the Q40 turbocharger bypass solenoid valve and connect the J-23738-A - Mityvac or a suitable vacuum gauge to the hose.

Note:

* Engine temperature, accessory load, and elevation level will affect engine vacuum.

* Vacuum readings will decrease by approximately 2.7 kPa (0.8 in Hg) for every 305 m (1,000 ft) of elevation above sea level.

3. Engine Idling, the gauge should read between 47-68 kPa (14-20 in Hg).

• If not within the specified range, inspect and repair the vacuum source or the vacuum leak in the areas listed below:

* The vacuum hose between the Q40 turbocharger bypass solenoid valve and the turbocharger bypass valve vacuum tank

* The turbocharger bypass valve vacuum tank

* The vacuum hose between the turbocharger bypass valve vacuum tank and the intake manifold

4. Ignition OFF, disconnect the J-23738-A - Mityvac or vacuum gauge and reconnect the hose to the Q40 turbocharger bypass solenoid valve

5. Disconnect the vacuum hose from the turbocharger bypass valve and connect the J-23738-A - Mityvac or a suitable vacuum gauge to the hose.

6. Engine Idling, command the turbocharger bypass solenoid valve between Active and Inactive with a scan tool while observing the vacuum gauge. The gauge should read between 47-68 kPa (14-20 in Hg) when commanded Active and 0 kPa (0 in Hg) when commanded Inactive.

• If not within the specified range, inspect the vacuum hose for a leak or restriction. If a condition is found, replace the hose. If a condition is not found, replace the Q40 turbocharger bypass solenoid valve.

7. Ignition OFF, inspect the turbocharger bypass valve assembly for damage. Refer to Turbocharger Cleaning and Inspection (LDK, LHU) Turbocharger Cleaning and Inspection.

• If a condition is found, replace the turbocharger bypass valve as necessary.

8. Disconnect the hose from the turbocharger wastegate actuator.

9. Connect the J-23738-A - Mityvac to the actuator and apply 51 kPa (15 inches Hg) of vacuum. The actuator should hold vacuum for at least 10 s

• If vacuum is not held for at least 10 s, replace the turbocharger

10. Using the exhaust/pressure port on the J-23738-A - Mityvac, or a suitable hand pressure pump, apply between 0-80 kPa (0-12 psi) pressure to the wastegate actuator. The wastegate actuator rod should move throughout the range.

• If the wastegate actuator rod does not move throughout the range, replace the turbocharger.

11. Disconnect the turbocharger wastegate solenoid valve supply hose at the turbocharger and connect the J-23738-A - Mityvac to the hose.

12. Apply 51 kPa (15 inches Hg) of vacuum to the Q42 turbocharger wastegate solenoid valve. Verify the pressure decreases to 0 kPa (0 inches Hg) when commanding the Turbocharger Wastegate Solenoid Valve to 25 % with a scan tool.

• If not the specified value, replace the Q42 turbocharger wastegate solenoid valve.

13. Inspect the turbocharger assembly for damage or foreign material. Refer to Turbocharger Cleaning and Inspection (LDK, LHU) Turbocharger Cleaning and Inspection.

• If a condition is found, repair or replace the turbocharger assembly as necessary.

Repair Instructions

Note: The Repair Verification must be performed after completing the repair.

* Charge Air Bypass Valve Replacement Charge Air Bypass Valve Replacement for turbocharger bypass valve replacement

* Turbocharger Replacement Turbocharger Replacement

* Turbocharger Control Solenoid Valve Replacement Turbocharger Control Solenoid Valve Replacement for turbocharger bypass solenoid valve replacement

* Turbocharger Wastegate Regulator Solenoid Valve Replacement Service and Repair

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

Repair Verification

1. Ignition OFF.

2. Install any components that have been removed or replaced during diagnosis.

3. Perform any adjustments, programming or setup procedures that are required when a component is removed or replaced.

Note: If the DTCs are not cleared the ECM will disable boost control and limit the system to mechanical boost only, resulting in a substantial decrease in engine power.

4. Clear the DTCs with a scan tool.

5. Ignition OFF and all vehicle systems OFF. It may take up to 2 minutes for all vehicle systems to power down.

6. If the repair was related to a DTC, duplicate the Conditions for Running the DTC and use the Freeze Frame/Failure Records, if applicable, in order to verify the DTC does not reset. If the DTC resets or another DTC is present, refer to the Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle and perform the appropriate diagnostic procedure.

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