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P0238






P0238-TURBO BOOST PRESSURE SENSOR CIRCUIT HIGH

For a complete wiring diagram, refer to the Wiring Information.





Theory of Operation

When the accelerator is closed suddenly, excessive boost pressure can build up between the Turbocharger and the Throttle Body which can cause damage to the Turbocharger. This can occur because the compressed air created by the Turbocharger has no place to go. This results in compressor surge. The Powertrain Control Module (PCM) detects this pressure increase via input from the Boost Pressure Sensor. The Boost Pressure Sensor operates as a typical three wire sensor. The PCM provides a 5-volt supply and sensor return circuit to the Boost Pressure Sensor and receives a feedback voltage on the signal circuit. The Turbocharger Surge Valve is responsible for venting the boost pressure between the Turbocharger and Throttle Body during sudden deceleration. The Turbocharger Surge Valve is normally spring loaded closed. When the PCM receives an input signal from the Boost Pressure Sensor that the pressure is above a calibrated amount, the PCM grounds the Turbocharger Surge Valve Control circuit which electrically opens the valve and routes the excess pressure between the Turbocharger and the Throttle Body back to the inlet of the Turbocharger, relieving the pressure and preventing compressor surge.

- When Monitored:
With the ignition on.

- Set Condition:
The (K37) Boost Pressure Sensor Signal circuit voltage is above 4.9 volts for 2.0 seconds.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

Diagnostic Test

1. DTC IS ACTIVE

NOTE: If there are any 5-Volt Reference DTCs present, repair those DTCs before proceeding with this test.

1. Turn the ignition on.
2. With the scan tool, erase PCM DTCs.
3. Turn the ignition off, wait 30 seconds, then start and idle the engine for at least two minutes.
4. With the scan tool, view PCM DTCs.

Is the status Active for this DTC?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test.

2. CHECK THE (F856) 5-VOLT SUPPLY CIRCUIT FOR A SHORT TO VOLTAGE
1. Turn the ignition off.
2. Disconnect the Boost Pressure Sensor harness connector.
3. Disconnect the PCM C2 harness connector.
4. Turn the ignition on.
5. Measure the voltage of the (F856) 5-Volt Supply circuit at the Boost Pressure Sensor harness connector.

Is the voltage reading above 5.2 volts?

Yes

- Repair the (F856) 5-Volt Supply circuit for a short to voltage.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 3

3. CHECK THE (K37) BOOST PRESSURE SENSOR SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE
1.
2. Measure the voltage of the (K37) Boost Pressure Sensor Signal circuit at the Boost Pressure Sensor harness connector.

Is the voltage reading above 5.2 volts?

Yes

- Repair the (K37) Boost Pressure Sensor Signal circuit for a short to voltage.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 4

4. CHECK THE (K900) SENSOR GROUND CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Turn the ignition off.
2. Measure the resistance of the (K900) Ground circuit between the Boost Pressure Sensor harness connector and the PCM C2 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 5

No

- Repair the (K900) Sensor Ground circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

5. CHECK THE BOOST PRESSURE SENSOR
1. Reconnect the Boost Pressure Sensor harness connector.
2. Reconnect the PCM C2 harness connector.
3. Turn the ignition on.
4. With the scan tool, clear DTCs.
5. Turn the ignition off.
6. Disconnect the Boost Pressure Sensor harness connector.
7. Connect a jumper between the (K900) Ground circuit and the (K37) Boost Pressure Sensor Signal circuit at the Boost Pressure Sensor harness connector.

NOTE: Be careful not to spread the terminals.

8. Turn the ignition on.
9. With the scan tool, select View DTCs.

NOTE: The scan tool should display the P0237-TURBO BOOST PRESSURE SENSOR CIRCUIT LOW DTC with the jumper connected.

Does the scan tool display P0237-TURBO BOOST PRESSURE SENSOR CIRCUIT LOW DTC as active or pending?

Yes

- Replace the Boost Pressure Sensor.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 6

6. POWERTRAIN CONTROL MODULE
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Boost Pressure Sensor and the Powertrain Control Module.
2. Look for any chafed, pierced, pinched, or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals.
4. Monitor the scan tool data relative to this circuit and wiggle test the wiring and connectors.
5. Look for the data to change or for the DTC to reset during the wiggle test.
6. Perform any Technical Service Bulletins that may apply.

Were any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace the Powertrain Control Module. .
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

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