P0238
DTC P0236, P0237, or P0238
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 Descriptor
DTC P0236 00
- Turbocharger Boost Sensor Performance
DTC P0237 00
- Turbocharger Boost Sensor Circuit Low Voltage
DTC P0238 00
- Turbocharger Boost Sensor Circuit High Voltage
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 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
* The ignition is ON or the engine is running.
* These DTCs runs continuously within the enabling conditions.
Conditions for Setting the DTC
P0237 00
The ECM detects that the boost pressure sensor voltage is less than 0.19 V for more than 4 s continuously, or 50 s cumulative
P0238 00
The ECM detects that the boost pressure sensor voltage is greater than 4.8 V for more than 4 s continuously, or 50 s cumulative.
Action Taken When the DTC Sets
* DTCs P0236 00, P0237 00 and P0238 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 P0236 00, P0237 00 and P0238 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.
* The BARO sensor is integrated within the ECM, and it has a port on the housing that allows it to sense the ambient pressure. Any restriction at this opening may hinder the operation of the BARO sensor.
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)
* Turbocharger System Description (LUJ) (Turbocharger 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. Ignition ON, observe the scan tool Manifold Absolute Pressure (MAP) Sensor parameter, the Boost Pressure Sensor parameter, and the BARO Sensor parameter.
2. Engine idling, observe the scan tool and compare the Boost Pressure Sensor parameter to the BARO Sensor parameter. They should be within 4 kPa (0.58 PSI) of each other.
3. Use the scan tool and compare the 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) of each other.
4. 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 housing.
* 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 smaller than 1 kPa (0.14 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 5 V reference circuit terminal 3. Verify the scan tool turbocharger Inlet Pressure Sensor is greater than 250 kPa (36.26 PSI).
• If smaller 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.
* Manifold Absolute Pressure Sensor Replacement (1.4L LUH and LUJ) (Service and Repair)
* Control Module References (Programming and Relearning)for ECM replacement, setup, and programming.