P0238 - TURBOCHARGER / SUPERCHARGER BOOTS HIGH CIRCUIT SENSOR

The PCM (Powertrain Control Module) uses a pulse control solenoid to control the amount of boost pressure, which is generated by the turbocharger. The PCM controls the pressure via a pressure sensor in the turbocharger. This sensor is a variable resistor, which has a 5-volt reference signal that is given by the Powertrain Control Module (PCM).

When the boost pressure is low, the resistance of the sensor is high, resulting in only a small percentage of the reference signal being returned to the PCM. As the pressure increases, the resistance decreases.  Thus, more of the reference signal returns to the PCM. This voltage variability is used by the PCM to calculate the actual boost pressure. The value of zero boost pressure is equal to approximately 0.5 volts. While the maximum boost is approximately 4.5 volts.

When the PCM detects that a boost pressure voltage exists, which is higher than 4 volts at a time when it was ordered unboosted, it sets the DTC code P0238 OBDII there.

• Turn on the service light on the Check Engine panel.
• During acceleration, the engine loses power.
• Loss of turbo pressure.

A P0238 OBD2 code can be generated by one or more of the following causes:

• There may be some DTC codes detected that are related to an intake air temperature sensor, engine coolant temperature sensor, or 5-volt reference.
• The problem may be in the wiring.
• A short circuit to the voltage in the sensor circuit.
• The PCM may be defective.

To solve the DTC code P0238, you can check the following components:

• Check the cable system for wear and tear and short circuits. Repair it and if necessary, replace it.
• You can disconnect the sensor and see if the short circuit disappears.
• Disconnect the sensor and by using a multimeter, verify that next to the input of the impulse sensor it has 5 volts of reference, if it does not have them, it indicates that the PCM is presenting inconsistency. In case it has this reference, reconnect the impulse sensor and you must measure the voltage on the opposite side of the connector and the voltage must be 0.5 volts, otherwise, the impulse sensor may be defective.