P0238
Turbocharger/Supercharger Boost Sensor A Circuit High
The appearance of the standard OBD2 trouble fault code P0238 is an indicator that your vehicle ECU triggered a threshold alert for "Turbocharger/Supercharger Boost Sensor A Circuit High". Understanding the root component breakdown helps avoid expensive diagnostic fees.
Driver's Summary
Code P0238 means your vehicle detected a problem with the turbocharger/supercharger boost sensor a circuit high system. In practice, this fault causes harsh engine cut-off under heavy acceleration, overboost condition. This is not a code to ignore — the underlying fault can rapidly worsen and lead to costly repairs if driving continues.
Symptoms
Harsh engine cut-off under heavy acceleration, overboost condition
Common Causes
- Stuck closed wastegate
- Short to voltage in boost sensor wiring
- Faulty boost control solenoid
- Defective boost sensor
How to Fix
- 1 Free up or replace wastegate actuator
- 2 Repair wiring short
- 3 Replace boost control solenoid
- 4 Replace boost sensor
Technical Explanation
The ECM detects code P0238 by continuously monitoring the relevant sensor circuit against calibrated threshold values stored in its non-volatile memory. The PCM monitors crankshaft rotational velocity via the CKP sensor at a resolution of individual tooth gaps on the reluctor ring. A combustion event in each cylinder produces a measurable acceleration spike; its absence or weakness is flagged as a misfire event within a 200-revolution or 1000-revolution test window. The MIL illuminates after the fault is confirmed on two consecutive drive cycles, and the freeze frame data captured at first detection is stored in the PCM's memory for diagnostic reference.
Is It Safe to Drive?
With P0238 active, your engine or transmission is not operating within design parameters. Short-term driving may seem fine, but internal damage is accumulating — particularly to stuck closed wastegate.
Mechanic's Pro Tip
For P0238, test the solenoid's coil resistance with a multimeter before ordering parts — most solenoids should read between 14 and 40 ohms; an open (infinite resistance) or short (near zero) confirms it's failed electrically. Also verify the PCM is commanding the solenoid by backprobing the connector with a test light during the relevant operating condition — if there's no command signal, the fault is in the PCM or wiring, not the solenoid itself.
Boost solenoid: $100 - $250; Wastegate actuator: $200 - $500