P0238: Turbo Boost Sensor A Circuit High (Meaning, Causes, Fixes)
What P0238 means
A turbocharger is driven by exhaust gas and pushes extra air into the engine, which is called boost. The engine computer (PCM) controls boost with a boost control solenoid and measures actual boost with a boost pressure sensor, per OBD-Codes.com. The PCM sends the sensor a 5-volt reference, and the sensor returns a signal of about 0.5 volts at zero boost rising to about 4.5 volts at maximum boost. OBD-Codes.com says P0238 sets when the PCM sees more than 4 volts at a time when no boost is being commanded, so the reading is impossibly high. It also notes manufacturer wording varies: GM calls it Turbocharger Boost Sensor Circuit High Voltage and Dodge/Chrysler call it MAP Sensor Voltage Too High. RepairPal describes it more broadly, saying the PCM sets P0238 when it detects an incorrect signal from the boost pressure sensor, without naming a voltage. Their cause lists also differ, as noted below.
Severity: can I keep driving?
Stop and fix promptly
RepairPal puts P0238 in its urgent category, meaning action is needed right away because it can cause severe damage or put the people in the car at risk. OBD-Codes.com says the condition should be corrected as soon as possible because of the increased risk of catalytic converter damage, and that the engine computer usually drops into a limp-home mode with a serious lack of acceleration. Allow extra room when merging or passing, and get it diagnosed soon. If the engine also runs rough, smells of fuel or the check engine light flashes, stop driving and have it checked. The turbo and exhaust get very hot, so let the engine cool before inspecting wiring or hoses near them.
Common symptoms
- Check engine light on (OBD-Codes.com)
- Serious lack of acceleration, because the PCM substitutes a generic boost value and limits boost and fuel timing, a limp-home mode (OBD-Codes.com)
- Decreased engine performance and lack of boost from the turbo or supercharger (RepairPal)
- Increased fuel consumption (RepairPal)
Likely causes
Roughly most to least common, based on the sources below. Your vehicle may differ.
- Faulty boost pressure sensor A (OBD-Codes.com; RepairPal's list reads 'brake booster pressure sensor failure', which appears to mean the boost pressure sensor its own description refers to)
- Short circuit to voltage on the sensor circuit (OBD-Codes.com)
- Intermittent wiring problems (both sources)
- Other codes for the intake air temperature (IAT) sensor, engine coolant temperature (ECT) sensor or the 5-volt reference circuit (OBD-Codes.com)
- Exhaust leak (RepairPal)
- Turbocharger or supercharger failure (RepairPal)
- Less often: a faulty PCM (both sources)
Diagnostic steps you can do
Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.
- Scan for other codes first. OBD-Codes.com says any IAT, ECT or 5-volt reference codes must be fixed before diagnosing P0238.
- Look up technical service bulletins (TSBs) for your year, make, model and engine; there may be a known fix.
- Inspect the boost sensor's connector and wiring for damage, chafing, corrosion or a loose fit.
- With the engine running, gently wiggle the sensor harness. OBD-Codes.com says if that brings the fault back, look closely at the connections at the sensors in that harness.
- Clear the code and see if it comes back on a test drive.
Typical fixes
- Repair the cause of any IAT, ECT or 5-volt reference codes first
- Repair damaged wiring or connectors, including a short to voltage on the sensor circuit
- Replace the boost pressure sensor
- Repair an exhaust leak, or a failed turbocharger or supercharger (RepairPal)
- Replace or reprogram the PCM only after the sensor and wiring check out
Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.
🛠 When to call a pro
- OBD-Codes.com's meter checks: with the sensor unplugged, key on and engine off, the reference feed should read 5 volts (if not, suspect the PCM); with it reconnected, the signal side should read about 0.5 volts (if not, suspect the sensor)
- OBD-Codes.com warns not to use an incandescent test light anywhere in the boost sensor circuit
- The sources disagree on scope: OBD-Codes.com defines a specific high-voltage condition (over 4 volts with no boost commanded) and focuses on the sensor, wiring and reference circuit, while RepairPal describes any incorrect sensor signal and adds exhaust leaks and turbo failure as causes
- RepairPal's general advice for this code: most trouble codes come from a sensor reporting an out-of-range value, and just replacing the sensor may not fix the underlying issue
Where to buy
Plain search links. Always match parts to your exact year, make, model and engine.
FAQs
Can I drive with P0238?
Carefully and not for long. RepairPal rates it urgent, and OBD-Codes.com says to correct it as soon as possible because of catalytic converter risk. The engine is usually in limp-home mode, so acceleration will be weak.
Is P0238 always a bad boost sensor?
No. OBD-Codes.com lists wiring problems, a short to voltage and related IAT, ECT or 5-volt reference faults, and says those other codes must be fixed first. RepairPal adds exhaust leaks and turbo failure.
What's the difference between P0238 and P0236?
P0236 is a range/performance code, meaning the boost reading doesn't make sense for the conditions. P0238 is a circuit high code: per OBD-Codes.com, the sensor voltage reads above about 4 volts when no boost is being commanded.
Sources
Last reviewed 2026-10-23. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.