P0299
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 00
- Engine Overboost
DTC P0299 00
- Engine Underboost
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System 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. 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 boost pressure sensor and integrated intake air temperature (IAT) sensor have the following circuits:
* 5 V reference
* Low reference
* Intake air pressure signal
* IAT sensor signal
The boost pressure 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 Barometric Pressure (BARO). When the vehicle is operated at wide open throttle (WOT) the turbocharger can increase the pressure to near 240 kPa (34.80 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 DTC
P0234 00
* DTCs P0237 00, or P0238 00 are not set.
* The driver requested boost pressure level exceeds the level of the base boost pressure.
* This DTC runs continuously within the enabling conditions.
P0299 00
* DTCs P0237 00, P0238 00, P0244 00, P0245 00, P0246 00, P2228 00, or P2229 00 are not set.
* The BARO is greater than 65 kPa (9.42 PSI).
* The engine speed is between 2 600-3 120 RPM.
* The ECM is not in limp home mode.
* The ECM is not in limp home mode with safety fuel cut-off activated.
* The driver requested boost pressure level exceeds the level of the base boost pressure.
* This DTC runs continuously within the enabling conditions.
Conditions for Setting the DTC
P0234 00
The ECM detects that the actual boost pressure is greater than the desired boost pressure for greater than 2 s.
P0299 00
The ECM detects that the actual boost pressure is less than the desired boost pressure continuously.
Action Taken When the DTC Sets
* DTCs P0234 00 and P0299 00 are Type C DTCs.
* The ECM will disable boost control and limit the system to mechanical boost only, resulting in a substantial decrease in engine power.
* The service vehicle soon indicator will illuminate.
Conditions for Clearing the DTC
DTCs P0234 00 and P0299 00 are Type C DTCs.
Diagnostic Aids
* The boost pressure sensor signal circuit is pulled high in the ECM. With the sensor disconnected, at ignition ON, a normal voltage measurement of the signal circuit with a DMM is 5.60 V.
* 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.
* 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 (Connector End Views By Name)
Description and Operation
* Boost Control System Description (LUJ) (Boost Control System Description)
* Boost Control System Description (LUJ) (Boost Control System Description)
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 (Programming and Relearning)for scan tool information
Circuit/System Verification
1. Verify that restrictions do not exist in the exhaust system. Refer to Restricted Exhaust (Restricted Exhaust).
2. Use the scan tool output controls to command the Turbocharger Bypass Solenoid Valve to 100% and then back to 0%. An audible series of clicks should be heard and felt between 20-90%.
3. Use the scan tool output controls to command the Turbocharger Wastegate Solenoid Valve to 100% and then back to 0%. An audible series of clicks should be heard and felt between 20-90%.
4. Use the scan tool and compare the Manifold Absolute Pressure (MAP) Sensor parameter to the Boost Pressure Sensor parameter during a WOT acceleration. The readings should be within 20 kPa (2.9 PSI) of each other.
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 system including all turbocharger components by inspecting for the following conditions:
* Any damaged components, including the turbocharger, the charge air cooler, and the Q42 Turbocharger Wastegate Solenoid Valve.
* Any hairline fractures of the B65 Intake Manifold Pressure and Air Temperature Sensor.
* Loose or improper installation of any components
* An air flow restriction
* Any vacuum leak
* Any pinholes or breaks in the vacuum hoses attached to the Q42 Turbocharger Wastegate Solenoid Valve.
* Any restrictions in the vacuum hoses attached to the Q42 Turbocharger Wastegate Solenoid Valve.
* Improper routing or connecting of the vacuum hoses on the charge air cooler, the Q40 Turbocharger Bypass Solenoid Valve, and the Q42 Turbocharger Wastegate Solenoid Valve.
* Any type of air leak between the turbocharger and the throttle body, including the charge air cooler assembly.
* Verify that an exhaust leak does not exist, including the mating surface area between the turbocharger and the exhaust manifold.
2. Ignition OFF, disconnect the harness connector at the B65 Intake Manifold Pressure and Air Temperature Sensor.
3. Ignition OFF for 90 s, test for less than 5 ohm between the low reference circuit terminal 1 and ground.
• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.
4. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal 3 and ground.
• If less than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.
• If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module.
5. Verify the scan tool Turbocharger Inlet Pressure Sensor parameter is greater than 275 kPa (39.9 PSI).
• If less than the specified range, test the signal circuit terminal 4 for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module.
6. Install a 3 A fused jumper wire between the signal circuit terminal 4 and the low reference circuit terminal 1. Verify the scan tool Turbocharger Inlet Pressure Sensor is less than 1 kPa (0.14 PSI).
• If greater than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.
7. If all circuits/connections test normal, replace the B65 Intake Manifold Pressure and Air Temperature Sensor.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
Control Module References (Programming and Relearning)for ECM replacement, setup, and programming