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
Circuit Description
The boost pressure sensor is integrated with the turbocharger boost/intake air temperature sensor. The boost 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. 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 engine is operated at wide-open throttle (WOT) the turbocharger can increase the pressure to near 240 kPa (34.8 psi). The pressure is equal to the BARO when the engine is idling or decelerating.
Conditions for Running the DTC
P0234 or P0299
* DTCs P0010, P0011, P0013, P0014, P0033, P0034, P0035, P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0111, P0112, P0113, P0114, P0116, P0117, P0118, P0119, P0121, P0122, P0123, P0128, P0222, P0223, P0234, P0236, P0237, P0238, P0243, P0245, P0246, P0299, P16F3, P2101, P2227, P2228, P2229 or P2230 are not set.
* Engine speed between 2,400-6,000 RPM.
* Desired boost pressure between 135-220 kPa (19.58-31.90 PSI).
* Ambient pressure between 60-120 kPa (8.70-17.40 PSI).
* Coolant temperature between -40 to +120°C (-40 to +248°F)
* Intake air temperature between -40 to +80°C (-40 to +176°F)
Conditions for Setting the DTC
P0234
The ECM detects that the actual boost pressure is greater than the desired boost pressure for greater than 1 s.
P0299
The ECM detects that the actual boost pressure is less than the desired boost pressure for greater than 2.2 s.
Action Taken When the DTC Sets
DTCs P0234 and P0299 are Type B DTCs.
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 DTC
DTCs P0234 and P0299 are Type B DTCs.
Diagnostic Aids
* The charged 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 duct work, the tightening specifications and proper positioning of the clamps is critical, and must be strictly adhered to.
* An excessively worn wastegate pivot pin may allow the wastegate to open slightly when commanded closed, which may result in P0299 being set.
Reference Information
Schematic Reference
Engine Controls Schematics [1][2]Electrical Diagrams
Connector End View Reference
Component Connector End Views Fuel Pump and Level Sensor Assembly
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
Circuit/System Verification
1. Ignition ON.
2. Verify DTC P0033, P0034, P0035, P0236, P0237, P0238, P0243, P0245, or P0246 is not set.
• If any of the DTCs are set
Refer to Diagnostic Trouble Code (DTC) List - Vehicle Diagnostic Trouble Code (DTC) List - Vehicle.
• If none of the DTCs are set
3. Verify the scan tool BARO Sensor parameter is within the range specified in the Altitude Versus Barometric Pressure Altitude Versus Barometric Pressure table for the current testing altitude.
• If the parameter is not within the range specified in the table.
Refer to DTC P2227-P2230 P2227.
• If the parameter is within the range specified in the table.
4. Verify the scan tool MAP Sensor and BARO Sensor parameters are within 3 kPa (0.4 psi).
• If the parameters are not within 3 kPa (0.4 psi).
Refer to DTC P0106 (LUV) P0106.
• If the parameters are within 3 kPa (0.4 psi).
5. Verify the scan tool Boost Pressure Sensor and BARO Sensor parameters are within 3 kPa (0.4 psi).
• If the parameters are not within 3 kPa (0.4 psi).
Refer to DTC P0236 P0236.
• If the parameters are within 3 kPa (0.4 psi).
6. Verify a click is heard or felt from the Q40 turbocharger bypass valve solenoid when commanding the Turbocharger Bypass Solenoid Valve between Active and Inactive with a scan tool.
• If a click is not heard or felt
Refer to Circuit/System Testing.
• If a click is heard or felt
7. Verify a series of clicks, which increase in frequency, are heard or felt from the Q42 turbocharger wastegate solenoid valve when commanding the Turbocharger Wastegate Solenoid Valve between 15-100 % with a scan tool.
• If a series of clicks in increasing frequency are not heard or felt
Refer to Circuit/System Testing.
• If a series of clicks in increasing frequency is heard or felt
8. Verify the scan tool MAP Sensor parameter and the Boost Pressure Sensor parameter are within 20 kPa (2.9 psi) during a WOT acceleration at the time of the 1-2 shift.
• If the parameters are not within 20 kPa (2.9 psi)
Refer to Circuit/System Testing.
• If the parameter are within 20 kPa (2.9 psi)
9. 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.
10. Verify a DTC does not set.
• If a DTC sets
Refer to Circuit/System Testing
• If a DTC does not set
11. All OK
Circuit/System Testing
1. Verify the conditions listed below do not exist:
* Loose clamps, cracks or other damage in the air intake duct system
* Collapsed or restricted intake duct system
* Restricted air filter
* Any air flow restriction
* Any 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 hoses going to the components listed below:
- Turbocharger wastegate solenoid valve
- Turbocharger bypass solenoid valve
- Intake manifold and turbocharger vacuum reservoir on the bottom of intake manifold
- Turbocharger
- Turbocharger wastegate
- Turbocharger bypass valve
* Missing, restricted or leaking exhaust components. Refer to Restricted Exhaust Restricted Exhaust
* Exhaust leak between the turbocharger and the exhaust manifold
* Restricted turbocharger oil supply line
* Loose or incorrect installation of any components
• If a condition exists
Repair or replace the affected component as necessary.
• If none of the conditions exist
2. Ignition OFF, disconnect the turbocharger wastegate solenoid valve supply hose at the turbocharger and apply 51 kPa (15 inches Hg) of vacuum to the hose with the GE 23738-A. Ignition ON.
3. Verify the pressure decreases to 0 kPa (0 inches Hg) when commanding the Turbocharger Wastegate Solenoid Valve to 15 % with a scan tool.
• The pressure does not decrease to 0 kPa (0 inches Hg)
Replace the Q42 turbocharger wastegate solenoid valve
• The pressure decreases to 0 kPa (0 inches Hg)
4. Connect the turbocharger wastegate solenoid valve supply hose to the turbocharger.
5. Disconnect the hose from the turbocharger wastegate actuator and connect the exhaust/pressure port of the GE 23738-A, or a suitable hand pressure pump, to the actuator.
6. Verify the wastegate actuator rod moves when applying pressure to the actuator.
• If the actuator does not move
1. Disconnect the wastegate actuator arm from the wastegate.
2. Verify the wastegate actuator rod moves when applying pressure to the actuator.
• If the actuator does not move, replace the turbocharger wastegate actuator
• If the actuator moves, replace the turbocharger
7. Disconnect the vacuum hose at the turbocharger bypass valve.
8. Install a vacuum gauge to the hose.
9. Engine Idling, verify the vacuum gauge displays between 51-67 kPa (15-20 inches Hq) of vacuum.
• The gauge does not display between 51-67 kPa (15-20 inches Hq) of vacuum.
Inspect and repair the leaking vacuum hose in the areas listed below:
* Between the turbocharger bypass valve and the turbocharger bypass solenoid valve
* Between the intake manifold and the turbocharger bypass solenoid valve
• The gauge displays between 51-67 kPa (15-20 inches Hq) of vacuum.
10. Disconnect the vacuum hose at the turbocharger vacuum reservoir on the bottom of intake manifold.
11. Connect the GE 23738-A to the vacuum reservoir and apply 34 kPa (10 inches Hg) of vacuum.
12. Verify the reservoir holds vacuum for at least 10 s.
• The reservoir does not hold vacuum for at least 10 s
Replace the intake manifold
• The reservoir holds vacuum for at least 10 s
13. Engine idling, vacuum gauge still installed from step 8, command the Turbocharger Bypass Solenoid Valve ON and OFF with the scan tool.
14. Verify the vacuum toggles between 0 kPa (0 inches Hg) when OFF to greater than 51 kPa (15 inches Hg) when ON.
• The vacuum does not toggle between 0-51 kPa (0-15 psi)
Replace the Q40 turbocharger bypass solenoid valve
• The vacuum toggles between 0-51 kPa (0-15 psi)
15. Verify the conditions listed below do not exist with the turbocharger assembly. Refer to Turbocharger Cleaning and Inspection Service and Repair
* Worn or damaged wastegate pivot pin
* Cracked, damaged or worn turbine blades
* Restricted wastegate, turbine, ports or passages
* Foreign material
• A condition exists
Repair or replace the turbocharger as necessary
• None of the conditions exist
16. Replace the turbocharger.
Repair Instructions
Perform the Diagnostic Repair Verification Verification Tests after completing the repair.
* Charge Air Bypass Regulator Solenoid Valve Replacement Charge Air Bypass Regulator Solenoid Valve Replacement
* Turbocharger Replacement Service and Repair
* Control Module References Control Module References for ECM replacement, programming and setup