Boost sensor signal wire shorted to a power source or to the sensor reference voltage wire; Failed boost sensor internally shorted, sending a high voltage on the signal line; Corroded, water-intruded, or loose sensor connector causing intermittent high voltage; Damaged wiring harness rubbed through against engine components or heat shields; PCM internal fault holding the signal circuit voltage high (rare but possible); Wrong sensor installed or a sensor that is not compatible with the vehicle's calibration

DTC codes / P02xx · Fuel and air metering (injector circuits) / P0238

P0238Turbocharger Boost Sensor A Circuit High

Q: What does code P0238 mean?

Turbocharger Boost Sensor A Circuit High. P0238 means the powertrain control module (PCM) has detected an abnormally high voltage on the signal circuit from the turbocharger boost sensor, also called the intake manifold pressure sensor. The sensor normally outputs a voltage that rises with boost pressure, so a high voltage tells the PCM the circuit is shorted to power, the sensor has failed, or the reference voltage is wrong.

P0238 means the powertrain control module (PCM) has detected an abnormally high voltage on the signal circuit from the turbocharger boost sensor, also called the intake manifold pressure sensor. The sensor normally outputs a voltage that rises with boost pressure, so a high voltage tells the PCM the circuit is shorted to power, the sensor has failed, or the reference voltage is wrong.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering (injector circuits)

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Reduced engine power or limp mode as the PCM limits boost to protect the turbocharger
Poor acceleration or sluggish throttle response because the PCM cannot accurately meter fuel
Black smoke from the exhaust or poor fuel economy from over-fueling
Rough idle or stalling in some cases when the sensor signal is pinned high
Turbocharger overboost or underboost symptoms depending on how the PCM reacts to the false high signal

Common causes, most likely first

Boost sensor signal wire shorted to a power source or to the sensor reference voltage wire
Failed boost sensor internally shorted, sending a high voltage on the signal line
Corroded, water-intruded, or loose sensor connector causing intermittent high voltage
Damaged wiring harness rubbed through against engine components or heat shields
PCM internal fault holding the signal circuit voltage high (rare but possible)
Wrong sensor installed or a sensor that is not compatible with the vehicle's calibration

How to diagnose and fix it

Connect a scan tool and read live boost sensor voltage and boost pressure data to confirm the high reading matches the code
Visually inspect the sensor connector and wiring for corrosion, water intrusion, chafing, or loose pins
Disconnect the sensor and check the signal circuit voltage with a multimeter; a high voltage with the sensor unplugged points to a wiring short
Check the sensor reference voltage and ground circuits for correct values, then test the sensor signal output with a vacuum pump or pressure source
Repair or replace any shorted or damaged wiring, then clear the code and verify the sensor voltage returns to a normal range
Replace the boost sensor if the wiring tests good but the sensor output stays high or does not respond to pressure changes
Clear codes and perform a road test with live data to confirm the repair and ensure no pending codes return

What a high boost sensor voltage really means

A shorted reference voltage wire inside the harness can feed five volts directly into the signal circuit, so always check the reference circuit before condemning the sensor.
Some technicians replace the boost sensor only to find the connector pins are pushed back or corroded, which mimics a failed sensor and sets P0238 again immediately.
P0238 can be set by a sensor that is mechanically stuck at a high reading rather than an electrical short, so live data under load is more revealing than a static key-on test.
A failing turbocharger wastegate or variable geometry actuator can cause actual overboost, but that usually sets overboost codes rather than a sensor circuit high code, so do not replace the turbo based on P0238 alone.
After any repair, the PCM may need several drive cycles with boost events before it will run its full self-test and turn off the light, so do not assume the fix failed if the code stays pending briefly.

Can I keep driving with P0238?

You can usually drive the vehicle to a repair shop, but avoid heavy acceleration and sustained boost because the PCM may be limiting power or over-fueling the engine. If the engine enters limp mode or runs poorly, stop driving and have it diagnosed promptly.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.