For 1990-2009 cars

### 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 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:

• | Engine speed

• | Throttle opening

• | Turbocharger boost pressure

• | Intake air temperature (IAT)

• | Barometric pressure (BARO)

• | Efficiency of the charge air cooler (CAC)

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

• | DTCs P0107, P0108, P0121, P0122, P0123, P0221, P0222, P0223, P0237, P0238, P2227, P2228, or P2229 are not set.

• | The engine OFF timer is greater than 4 seconds.

• | The engine is cranking at less than 400 RPM for at least 200 ms.

• | This DTC runs during engine cranking only.

#### P0236 - Engine Idling

• | DTCs P0121, P0122, P0123, P0221, P0222, P0223, P0237, P0238, P2227, P2228, or P2229 are not set.

• | The engine is running and the ECM has counted greater than three revolutions.

• | The engine speed is less than 1000 RPM.

• | The TP Sensor parameter is less than 24 percent.

• | The ECM is not in limp home mode.

• | This DTC runs continuously within the enabling conditions.

#### P0237

• | The ignition is ON or the engine is running.

• | This DTC runs continuously within the enabling conditions.

#### P0238

• | The ignition is ON or the engine is running.

• | This DTC runs continuously within the enabling conditions.

### 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

• | The ECM detects when the engine is idling that the boost pressure sensor signal is less than 50 kPa for greater than 4 seconds continuously, or 50 seconds cumulative.

| OR

• | The ECM detects when the engine is idling that the boost pressure sensor signal plus a calibrated threshold is not within range of the BARO sensor for greater than 4 seconds continuously, or 50 seconds cumulative.

#### 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

• | 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

#### Connector End View Reference

Component Connector End Views

#### 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. 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.

• | Turbocharger Pressure Sensor Replacement

• | Control Module References for engine control module replacement, setup, and programming