OBD-II Code · Sensors
P0238
Turbo Boost Sensor A High
Severity
medium
Worth booking. It costs fuel, emissions or comfort until it is fixed.
Can you drive it
Only if running normally
A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety.
Indicative cost (USD)
$150–$400
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
Boost sensor voltage high.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
- Overboost symptoms
Likely causes
- Failed sensorMost common
- Short to power
Read the full diagnostic procedureP0238 is the boost sensor A circuit high fault, set when the sensor signal voltage exceeds the calibrated upper threshold, typically above 4.8 volts…
P0238 is the boost sensor A circuit high fault, set when the sensor signal voltage exceeds the calibrated upper threshold, typically above 4.8 volts on a 0 to 5 volt sensor.
Cheapest first
- scan the sensor at key-on-engine-off; a reading pinned at 4.9 to 5.0 volts or showing pressure well above atmospheric (over 18 psi absolute at sea level) indicates a circuit or sensor fault.
- Disconnect the sensor and verify the signal voltage drops to 0 volts at the ECM connector; if it stays high, you have a short between the signal wire and the 5-volt reference.
- If signal drops correctly with the sensor unplugged, the sensor itself is faulty.
- Check the ground pin: an open ground at the sensor will float the signal voltage to the rail.
- Inspect the connector for water intrusion and corrosion, especially on under-hood sensors mounted near the front of the engine bay where water spray is common.
- Caveat: a mechanical overboost condition where actual boost truly does exceed the sensor's calibrated range can set P0238 with a perfectly good sensor, so verify with a mechanical boost gauge if no wiring fault is found.
Vehicle-specific patternsFord 6.0L and 6.4L Power Stroke (2003-2010) sees P0238 from boost sensor connector corrosion.
- 2003-2010Ford 6.0L and 6.4L Power Stroke sees P0238 from boost sensor connector corrosion. Cummins ISB 6.7L (2007-2018 Ram HD) sets P0238 from boost sensor harness chafe at the turbo support bracket.
- 2008-2017VW/Audi 2.0T TFSI sees P0238 from manifold pressure sensor failure and connector wear.
- 2009-2016Mercedes OM651 2.1 CDI sets P0238 from boost sensor failure as a maintenance item.
Estimated repair$40 to $350.
Look up another code
P0238 — frequently asked
What does a P0238 code mean?
Boost sensor voltage high.
What causes a P0238 code?
Common causes: Failed sensor; Short to power.
What are the symptoms of a P0238 code?
Typical symptoms: Check engine light; Overboost symptoms.
Is it safe to drive with a P0238 code?
Only if running normally. A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety. Estimated repair: $150-$400.
How do I diagnose a P0238 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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