Buick Regal: DTC P0237 or P0238

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 P0237

Turbocharger Boost Sensor Circuit Low Voltage

DTC P0238

Turbocharger Boost Sensor Circuit High Voltage

Diagnostic Fault Information

Typical Scan Tool Data

Boost Pressure Sensor

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

• Ignition is ON or the engine is running.
• The DTCs run continuously when the above conditions have been met.

Conditions for Setting the DTC

P0237

The ECM detects that the boost pressure sensor voltage is less than 0.9 V for greater than 5 s.

P0238

The ECM detects that the boost pressure sensor voltage is greater than 3.9 V for greater than 5 s.

Action Taken When the DTC Sets

• DTCs P0237 and P0238 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 MIL/DTC

DTCs P0237 and P0238 are Type B DTCs.

Reference Information

Schematic Reference

Engine Controls Wiring Schematics (LTG)

Connector End View Reference

Component Connector End View Index

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. Verify that DTC P0641, P0651, P0697, P06A3, or P06D2 is not set.

• If a DTC is set

Refer to Diagnostic Trouble Code (DTC) List - Vehicle.

• Go to next step: If none of the DTCs are set

2. Verify the scan tool BARO parameter is within the range specified in the Altitude Versus Barometric Pressure table, for the current vehicle testing altitude.

• BARO is not in range

Refer to DTC P2227-P2230.

• Go to next step: BARO is within range

3. Verify the scan tool Boost Pressure Sensor pressure and BARO parameters are within 3 kPa (0.4 psi).

• The parameters are not within 3 kPa (0.4 psi).

Refer to Circuit/System Testing

• Go to next step: The parameters are within 3 kPa (0.4 psi).

4. 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.

• The parameters are not within 20 kPa (2.9 psi)

Refer to Circuit/System Testing.

• Go to next step: The parameters are within 20 kPa (2.9 psi)

5. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

6. Verify a DTC does not set.

• If the DTC sets

Refer to Circuit/System Testing.

• Go to next step: If the DTC does not set

7. All OK.

Circuit/System Testing

1. Ignition OFF, and all vehicle systems OFF, disconnect the harness connector at the B111B turbocharger boost/intake air temperature sensor. It may take up to 2 minutes for all vehicle systems to power down.

2. Test for less than 5 Ω between the low reference circuit terminal 1 and ground.

• If 5 Ω or greater

1. Ignition OFF, disconnect the X1 harness connector at the K20 engine control module.
2. Test for less than 2 Ω in the low reference circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K20 engine control module.

• Go to next step: If less than 5 Ω

3. Ignition ON.

4. Test for 4.8 - 5.2 V between the 5 V reference circuit terminal 3 and ground.

• If less than 4.8 V

1. Ignition OFF, disconnect the X1 harness connector at the K20 engine control module.
2. Test for infinite resistance between the 5 V reference circuit and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the 5 V reference circuit end to end.
   • If 2 Ω or greater, repair the open/high resistance in the circuit.
   • If less than 2 Ω, replace the K20 engine control module

NOTE: If the signal circuit is shorted to a voltage the engine control module or the sensor may be damaged.

• If greater than 5.2 V

1. Ignition OFF, disconnect the X1 harness connector at the K20 engine control module, ignition ON.
2. Test for less than 1 V between the 5 V reference circuit and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K20 engine control module.

• Go to next step: If between 4.8 - 5.2 V

5. Verify the scan tool Boost Pressure Sensor voltage parameter is less than 0.2 V.

• If 0.2 V or greater

1. Ignition OFF, disconnect the X1 harness connector at the K20 engine control module, ignition ON.
2. Test for less than 1 V between the signal circuit terminal 4 and ground.
   • If 1 V or greater, repair the short to voltage on the circuit.
   • If less than 1 V, replace the K20 engine control module.

• Go to next step: If less than 0.2 V

6. Install a 3 A fused jumper wire between the signal circuit terminal 4 and the 5 V reference circuit terminal 3.

7. Verify the scan tool Boost Pressure Sensor voltage parameter is greater than 4.5 V.

• If 4.5 V or less

1. Ignition OFF, disconnect the X1 harness connector at the K20 engine control module.
2. Test for infinite resistance between the signal circuit terminal 4 and ground.
   • If less than infinite resistance, repair the short to ground on the circuit.
   • Go to next step: If infinite resistance
3. Test for less than 2 Ω in the signal circuit end to end.
   • If 2 Ω or greater, repair the open or high resistance in the circuit.
   • If less than 2 Ω, replace the K20 engine control module.

• Go to next step: If greater than 4.5 V

8. Test or replace the B111B turbocharger boost/intake air temperature sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Intake Air Pressure and Temperature Sensor Replacement for turbocharger boost/intake air temperature sensor replacement
• Control Module References for ECM replacement, programming, and setup

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