P0238 — Turbocharger Boost Sensor A Circuit High

powertrain (engine/transmission)

Is it safe to drive?

Service soon and avoid sustained boost P0238 can cause the ECU to limit engine output even when actual boost is normal. Short trips may be possible, but avoid hard acceleration until the circuit is repaired. If the boost gauge shows genuine overboost, the engine hesitates, or the vehicle enters a severe fail-safe mode, stop safely and tow for diagnosis.

Typical symptoms

The check engine light illuminates and the ECU stores P0238
The displayed boost pressure may be implausibly high, fixed, or fluctuate erratically
The vehicle enters a reduced-power or boost fail-safe mode under acceleration
Acceleration may feel hesitant, soft, or limited even when the engine is under load
Unusual turbocharger whistling or boost-control solenoid activity may be noticed

Common causes

Boost sensor A has an internal failure that biases its output signal high
The sensor signal wire is open or has high resistance, allowing the ECU pull-up voltage to register as an excessive boost reading
The sensor signal wire is shorted to a constant voltage such as the 5-volt reference circuit
The sensor connector is corroded, loose, damaged, or has a pushed-back terminal
A poor sensor ground or excessive voltage drop in the ground circuit creates an implausibly high signal
An incorrect or improperly calibrated replacement boost sensor is installed
A damaged ECU input or internal boost-control module fault occurs after the wiring and sensor tests pass

How to diagnose with an OBD scanner

Confirm P0238 and capture operating data Connect an ELM327 adapter and use AIScanAuto or another scan tool to confirm P0238. Review freeze-frame data and, if supported, live commanded boost versus measured boost. Record whether the high reading appears immediately, during acceleration, or only with the wiring harness disturbed.
Inspect boost sensor A and its wiring Locate boost sensor A using the vehicle wiring diagram. Inspect the connector and harness for corrosion, cracked plugs, pinched wires, heat damage, and terminals that are loose or pushed back. Repair damaged wiring or terminals before replacing the sensor.
Measure the complete sensor circuit Back-probe the sensor and ECU connectors with a multimeter. Verify the specified reference voltage, sensor ground, and signal voltage at the same time. Perform a voltage-drop test on the ground and wiggle the harness while watching for signal changes. Compare all results with the manufacturer service information rather than assuming a universal voltage value.
Test the boost sensor If the wiring and grounds are sound, test boost sensor A against its specified response curve or substitute a known-good sensor with the correct part number and calibration. A generic MAP sensor may not be interchangeable. A correct replacement should stop the high P0238 signal without creating another boost-related code.
Validate the repair under load Clear the stored code, then repeat the conditions that originally triggered P0238. Confirm that commanded and measured boost agree, the gauge moves normally, and P0238 does not return in pending or stored memory. If the signal remains high, continue testing the ECU input and connector pins; stop testing if actual boost rises above the specified limit.

Approximate repair cost

A typical independent-shop estimate for P0238 diagnosis and repair is $150–$700 USD. Sensor replacement commonly falls near $100–$300 including labor, while harness or connector repairs can add approximately $100–$400. These figures are estimates and vary by region, labor rate, and vehicle access.

Common questions

Does P0238 prove that the turbocharger failed?

No. P0238 identifies a high circuit signal from boost sensor A, and the fault may be the sensor, connector, wiring, ground, or ECU input. The turbocharger should not be condemned from this code alone.

Can the vehicle be driven with P0238?

It may be driven cautiously because the ECU can reduce boost as a fail-safe, but sustained acceleration is not advisable. Repair P0238 promptly, especially if the gauge shows high boost or the engine loses power.

Is P0238 the same as a low-boost fault?

No. P0238 means the boost sensor circuit is reporting an implausibly high signal. Low or reduced boost can occur afterward as a protective response to that false high reading, but it is a different condition.

Why might P0238 return after the code is cleared?

Clearing the code does not correct a defective sensor, shorted wire, poor ground, or damaged terminal. P0238 will return whenever the high-signal condition remains, so the circuit must be tested and repaired before the code is considered resolved.

When your scanner pulls code P0238, the engine control unit has determined that the turbocharger boost sensor is reporting a voltage outside acceptable parameters. Specifically, the control module sees the signal wire sitting at or near battery voltage when it should be reading much lower under normal operating conditions. This falls under powertrain faults and indicates the ECU has compared live sensor data against its factory calibration and found the reading abnormally high.

The turbo boost sensor plays a critical role in how your engine manages forced induction. It feeds real-time manifold pressure data back to the ECU, which then adjusts fuel delivery, timing, and wastegate operation to maintain proper boost levels. When this sensor circuit reads high, the computer loses accurate boost feedback. The ECU responds by triggering P0238, storing freeze-frame data of engine conditions at the moment the fault occurred. This snapshot—showing RPM, load, coolant temperature, and speed—gives you a starting point for diagnosis.

P0238 typically sets after multiple drive cycles, not on a single glitch. The engine may activate reduced-power mode as a protective measure. Common triggers include a failing boost sensor pulling the signal wire high, wiring damage causing a short to power, broken ground paths, or mechanical issues with wastegate operation. Boost pressure irregularities from leaks or component wear can also force the sensor circuit out of range.

Common Symptoms of P0238

Check Engine Light illuminates on the dashboard
Noticeable reduction in engine power, especially under acceleration
Vehicle enters limp-home mode with restricted performance
Black exhaust smoke during hard acceleration
Unusual whistling, hissing, or siren-like sounds from the engine bay
Elevated oil consumption as the engine compensates for improper air-fuel ratios

Common Causes of P0238

Faulty turbocharger boost sensor internally shorting the signal circuit
Signal wire shorted directly to battery positive voltage
Open or corroded ground connection at the boost sensor
Stuck or malfunctioning wastegate and associated boost control solenoid
Damaged vacuum lines or actuator hoses feeding the turbo system
Boost pressure leaks in intercooler piping, cracked hoses, or loose clamps
Clogged intake tracts or exhaust restrictions such as a loaded DPF or failing catalytic converter
Worn or mechanically failed turbocharger unit

How to Diagnose P0238

Connect an OBD2 scanner and confirm P0238 is stored. Record the freeze-frame data—this captures engine conditions when the fault triggered and guides your testing.
Scan for any related diagnostic trouble codes. Secondary codes often expose the root cause. Cross-reference manufacturer technical service bulletins for your vehicle make and model; software updates or known fixes may apply to your specific application.
Perform a visual inspection of the turbocharger boost sensor harness and connectors. Look for frayed insulation, corrosion at the terminals, chafing from heat or movement, and ensure the connector seats securely.
With the sensor unplugged, measure voltage at the harness signal pin. A reading near battery voltage confirms a short to power in the wiring. If the reading drops to normal range with the sensor disconnected, the component itself has failed.
Pressurize the intake system and check for boost leaks. Inspect intercooler hoses, clamps, and seals for cracks or dislodgment—these are frequent culprits.
Actuate the boost control solenoid with your scanner while monitoring wastegate response. Lack of movement indicates electrical or mechanical failure in the solenoid or actuator.
Clear P0238 and complete a full drive cycle matching the freeze-frame conditions. Confirm the code does not return, which validates a successful repair.

Repair Options and Costs

Repair costs vary significantly depending on which component failed:

Repair boost leak in hoses, clamps, or intercooler: $100–$400
Replace boost control solenoid or actuator: $200–$600
Replace turbocharger boost sensor: $150–$350
Replace turbocharger unit: $1,200–$3,500

Total Cost to Fix P0238

Most P0238 repairs fall between $100 and $600 when addressing boost leaks, solenoid faults, or sensor failures. Full turbocharger replacement—the most expensive scenario—runs $1,200 to $3,500 including parts and labor at independent shop rates. A methodical diagnosis before purchasing parts prevents unnecessary expense; the most severe repair is rarely the first one to investigate.

Driving Safety Verdict

Caution applies. P0238 typically leaves your vehicle drivable but noticeably down on power, often in limp-home mode. Repeated hard acceleration with inaccurate boost feedback risks engine overheating and accelerated turbo wear. Limit boost demands and schedule repair promptly—delaying diagnosis can escalate a $200 fix into a $2,000 turbo replacement.