Diagnostic Instructions

DTC Descriptors

DTC P0236: Turbocharger Boost System Performance

DTC P0237: Turbocharger Boost Sensor Circuit Low Voltage

DTC P0238: Turbocharger Boost Sensor Circuit High Voltage

Diagnostic Fault Information

Circuit	Short to Ground	High Resistance	Open	Short to Voltage	Signal Performance
5-Volt Reference	P0107, P0236, P0642	P0236, P0237	P0107, P0236	P0036, P0236, P0606, P0643	P0234, P0236, P0299
Boost Pressure Sensor Signal	P0237	P0236, P0237	P0238	P0238	P0236
Low Reference	--	P0234, P0236, P0238	P0238	--	--

Typical Scan Tool Data

Intake Air Pressure and Temperature Sensor

Circuit	Short to Ground	Open	Short to Voltage
Operating Conditions: Engine running at various operating conditions Parameter Normal Range: BARO to 240 kPa
5-Volt Reference	20-80 kPa	30-80 kPa	20-80 kPa
Intake Air Pressure Sensor Signal	0 kPa	276 kPa	276 kPa
Low Reference	--	276 kPa	--

Circuit 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. Pressure in this portion of the induction system is affected by the following:

The sensor provides a signal voltage to the engine control module (ECM), relative to the pressure changes, on the boost pressure sensor 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. 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

P0236 - Engine Cranking

P0236 - Engine Idling

P0237

P0238

Conditions for Setting the DTC

P0236 - Engine Cranking

The ECM detects when the engine is cranking that the boost pressure sensor signal plus a calibrated threshold is not within range of a model derived from the BARO sensor, the MAP sensor, and the boost pressure sensor for more than 2 seconds.

P0236 - Engine Idling

P0237

The ECM detects that the boost pressure sensor voltage is less than 0.19 volt for more than 4 seconds continuously, or 50 seconds cumulative.

P0238

The ECM detects that the boost pressure sensor voltage is greater than 4.85 volts for more than 4 seconds continuously, or 50 seconds cumulative.

Action Taken When the DTC Sets

DTCs P0236, P0237, P0238, are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTCs P0236, P0237, P0238, are Type B DTCs.

Diagnostic Aids

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Turbocharger System Description

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1. Ignition ON, observe the diagnostic trouble code (DTC) information with a scan tool. Verify that DTCs P0641, P0642, P0643, P2227, P2228, or P2229 are not set.

⇒	If any of the above DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.

2. Compare the scan tool BARO parameter to the Altitude Versus Barometric Pressure table. The BARO should be within the specified range displayed in the table for the specific altitude.

⇒	If not within the specified range, refer to DTC P2227, P2228, or P2229 for further diagnosis.

3. 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

•	Boost pressure sensor damage

•	MAP sensor damage

•	A buildup of contamination, snow or ice at the BARO port on the ECM

•	Loose or improper installation

•	An air flow restriction

•	Any vacuum leak

•	Any type of air leak between the turbocharger and the throttle body

•	An exhaust leak

⇒	If a condition is found, repair as necessary.

2. Ignition OFF, disconnect the harness connector at the B65 intake air pressure and temperature sensor.
3. Ignition OFF, remove the fuse that supplies B+ to circuit terminal 56 X2 of the ECM.
4. Test for less than 5 Ω 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 ECM.

5. Install the fuse that supplies B+ to circuit terminal 56 X2 of the ECM.
6. Ignition ON, test for 4.8-5.2 V between the 5-volt reference circuit terminal 3 and ground.

⇒	If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 ECM.

⇒	If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the K20 ECM.

7. Verify the scan tool Boost Pressure Sensor parameter is greater than 275 kPa.

⇒	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 ECM.

8. Install a 3 A fused jumper wire between the signal circuit terminal 4 and the low reference circuit terminal 1. Verify the scan tool Boost Pressure Sensor parameter is less than 1 kPa.

⇒	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 ECM.

9. If the circuits test normal, test or replace the B65 intake air pressure and temperature sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.