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, P0193, P0236, P0642 | P0236, P0237 | P0107, P0236 | P0036, P0193, P0236, P050A, P0606, P0643 | P0234, P0236, P0299
Boost Pressure Sensor Signal | P0237 | P0236, P0237 | P0238 | P0238 | P0236
Low Reference | -- | P0234, P0236, P0238 | P0098, P0099, P0238 | -- | --

### Typical Scan Tool Data

#### Boost Pressure Sensor

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: Engine running Parameter Normal Range: BARO to 240 kPa
5-Volt Reference | 20-80 kPa | 30-80 kPa | 20-80 kPa
Boost Pressure Sensor Signal | 0 kPa | 276 kPa | 276 kPa
Low Reference | -- | 276 kPa | --

### Circuit Description

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 (CAC). A diaphragm within the sensor is displaced by the pressure changes that occur from the varying load and operating conditions of the engine. The sensor translates this action into electrical resistance. The boost pressure sensor has the following circuits:

• | A shared and regulated 5-volt reference circuit

• | A shared low reference circuit

• | A boost pressure sensor signal circuit

• | The IAT sensor 2 signal circuit

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

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. The ECM monitors the boost pressure sensor signal for performance and for pressure outside of the normal range.

### Conditions for Running the DTC

#### P0236 - Engine Cranking

• | DTCs P0107, P0108, P0121, P0122, P0123, P0221, P0222, P0223, P0237, P0238, P2227, P2228, 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, 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

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

### Conditions for Clearing the MIL/DTC

DTC P0236, P0237, P0238, are Type B 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 volts.

• | A restriction in the boost pressure sensor port will cause the sensor to be sluggish or unresponsive.

• | Verify that the sensor is properly installed and tightened to the proper specification.

• | The CAC 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 ductwork, 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.

• | A restriction that exists in the exhaust system will hinder the performance of the engine and the turbocharger. Refer to Restricted Exhaust .

• | For additional turbocharger and boost system information, refer to Turbocharger System Description and Boost Control System Description .

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

• | Engine Control Module Connector End Views

• | Engine Controls Connector End Views

#### 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

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Scan Tool Output Controls

• | Scan Tool Snapshot Procedure

### Circuit/System Verification

Important: Verify that the engine is in good mechanical condition before continuing with this diagnostic.

• | Verify the integrity of the entire air induction system by inspecting for the following conditions:

- | Any damaged components, including the turbocharger and the TC wastegate solenoid

- | Any hairline fractures of the boost pressure sensor housing

- | Loose or improper installation

- | An air flow restriction

- | Any vacuum leak

- | Improper routing or connecting of any vacuum hoses, including those on the turbocharger bypass valve solenoid and the turbocharger wastegate solenoid

- | In cold climates, inspect for any snow or ice buildup

• | Determine the current vehicle testing altitude. Ignition ON, observe the scan tool MAP Sensor parameter, the Boost Pressure Sensor parameter, and the BARO Sensor parameter. Compare the parameters to each other and to the Altitude versus Barometric Pressure Table. Refer to Altitude Versus Barometric Pressure .

• | Engine idling, observe the scan tool and compare the Boost Pressure Sensor parameter to the BARO Sensor parameter. They should be within 4 kPa of each other.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the boost pressure sensor.
2. Ignition OFF for 90 seconds, test for less than 5 ohms of resistance between the low reference circuit terminal A 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 ECM.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal C 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 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 ECM.

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

⇒ | If less than the specified range, test the signal circuit terminal D for a short to ground. If the circuit tests normal, replace the ECM.

5. Install a 3A fused jumper wire between the signal circuit terminal D and the low reference circuit terminal A. 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 ECM.

6. If the circuits test normal, replace the boost pressure sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Intake Air Pressure and Temperature Sensor Replacement

• | Control Module References for ECM replacement, setup, and programming