P0238

DTC P0238 Turbocharger (TC) Boost Sensor Circuit High Voltage






Circuit Description

The PCM sends a 5 volt reference signal to the boost sensor. As manifold pressure changes, the electrical resistance of the boost sensor also changes. By monitoring the sensor output voltage, the PCM detects how much pressure is being produced by the turbocharger in the intake manifold. The PCM uses the boost sensor to control turbo boost and fuel at different loads. This is a type B DTC.

Conditions for Setting the DTC

^ Boost Pressure greater than or equal to 4.8 volts (202 kPa).
^ Engine Speed less than 3506 RPM.

Action Taken When the DTC Sets

No turbo boost.

Conditions for Clearing the MIL/DTC

^ The PCM will turn the MIL off after three consecutive trips without a fault condition.
^ A History DTC will clear when forty consecutive warm-up cycles that the diagnostic does not fail (coolant temperature has risen Soc (40°F) from start up coolant temperature and engine coolant temperature exceeds 71°C (160°F) that same ignition cycle).
^ Use of a Scan Tool.

Diagnostic Aids

With the ignition "ON" and the engine stopped, boost pressure is approximately equal to Baro. Comparison of this reading with known good vehicle using the same sensor is a good way to check accuracy of a "suspect" sensor. Readings should be the same +.4 volt. Very little boost can be attained by revving the engine in neutral. A J-39200 can be used to measure (actual) signal voltage at the PCM harness connector.

Test Description

Number(s) below refer to the number(s) on the diagnostic table.

2. This step simulates conditions for a DTC P0237. If the PCM recognizes the change, the PCM and the signal circuit are OK.

3. This step will make sure the PCM is responding to a low signal voltage. This will indicate that the PCM is OK.