P0239🔧 Turbo/supercharger boost pressure sensingStop and fix promptly

P0239: Turbocharger/Supercharger Boost Sensor B Circuit (Meaning, Causes, Fixes)

Reviewed 2026-10-26 · Based on 2 cited source(s)

What P0239 means

On a turbocharged or supercharged engine, a boost pressure sensor tells the engine control module (ECM or PCM) how much boost the turbo or supercharger is actually making. P0239 points to boost sensor "B"; engines with a second turbo or a second boost sensor use the B codes. RepairPal says P0239 sets when the PCM detects an incorrect signal from the boost pressure sensor. OBD-Codes.com describes it as an unacceptable difference between the boost the ECM has programmed for a given RPM and the value the sensor reports, and says the code is basically identical to P0235, which covers the "A" turbocharger. (One line of the OBD-Codes.com article says sensor A circuit, but its title and its note comparing it to P0235 make clear it covers sensor B.) P0239 is the general circuit code for boost sensor B. P0240 is its range/performance code, P0241 is circuit low and P0242 is circuit high, per RepairPal's code list. The sources' cause lists differ: OBD-Codes.com focuses mostly on mechanical turbo problems (wastegate, bearings, oil supply, boost leaks, intercooler) before the sensor wiring, while RepairPal lists a brake booster pressure sensor failure and an exhaust leak, which OBD-Codes.com does not mention.

Severity: can I keep driving?

Stop and fix promptly

Get it checked soon and drive gently until you do. RepairPal rates P0239 Urgent, meaning immediate action is needed. OBD-Codes.com says turbo problems should be addressed as soon as possible because a turbocharged engine greatly exaggerates engine problems.

Common symptoms

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

  1. A wiring problem: a short or open in the harness between the boost sensor and the computer, or a poor connection at the sensor (OBD-Codes.com, RepairPal)
  2. A faulty boost sensor, or a faulty 5 volt reference driver in the ECM (OBD-Codes.com)
  3. A turbocharger or supercharger failure, such as worn bearings, damaged blades, excess shaft end play, a cracked housing or an oil seal leak (OBD-Codes.com, RepairPal)
  4. A wastegate stuck open, stuck closed or leaking (OBD-Codes.com)
  5. Poor oil supply to the turbo bearing from a blocked feed or return line (OBD-Codes.com)
  6. A boost or vacuum leak: loose intake pipe connections, a vacuum leak at the intake manifold or a defective intercooler (OBD-Codes.com)
  7. A dirty air filter (OBD-Codes.com)
  8. An exhaust leak, including loose exhaust manifold to turbo bolts (OBD-Codes.com, RepairPal)
  9. A brake booster pressure sensor failure (RepairPal only)
  10. A faulty PCM (RepairPal; OBD-Codes.com mentions the ECM 5 volt reference)

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

  1. Scan for other codes first and make sure the engine runs well with no misfires. OBD-Codes.com says to confirm there are no misfire or knock sensor codes before blaming the turbo.
  2. On a cold engine, check the hose clamps at the turbo outlet, intercooler and throttle body for tightness, and look for intake and vacuum hose leaks.
  3. Check that the turbo is tight on its exhaust flange and look for exhaust leaks around the turbo.
  4. Check the air filter and replace it if it's dirty.
  5. Inspect the oil feed and return lines to the turbo for leaks or kinks. With the engine cool and the outlet hose off, OBD-Codes.com says to look for blades rubbing the housing, bent blades or oil inside the turbo, and spin it by hand to feel for grinding.
  6. If the turbo checks out, test the boost sensor circuit with a multimeter using your service manual. OBD-Codes.com says to confirm the 5 volt reference from the computer (no voltage points to the harness or the computer) and then check that the sensor's signal voltage rises with RPM (no rise points to the sensor).
  7. OBD-Codes.com also describes vacuum and boost gauge tests with specific numbers, but boost specs vary a lot between engines, so use the figures in your vehicle's service manual.

Typical fixes

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

  • The engine has very low power or goes into limp mode
  • You hear new turbo whine, grinding or rattling, or see blue or heavy smoke
  • The turbo shows oil inside, blade damage or shaft play
  • You don't have a service manual, multimeter or boost gauge
  • The code comes back after the wiring and sensor check out

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Can I drive with a P0239 code?

Only gently and not for long. RepairPal rates it Urgent, and OBD-Codes.com says turbo problems should be addressed as soon as possible because a turbocharged engine exaggerates engine problems.

Is P0239 a bad boost sensor or a bad turbo?

It can be either, or neither. OBD-Codes.com starts with turbo, wastegate and boost-leak checks and then tests the sensor circuit, while RepairPal lists wiring, the turbo, an exhaust leak, a brake booster pressure sensor and the PCM. Check the cheap things first before buying parts.

What is the difference between P0235 and P0239?

Both mean the boost the computer reads doesn't match what it expects. OBD-Codes.com says P0239 is basically identical to P0235, except P0235 covers boost sensor A and P0239 covers boost sensor B. The B sensor codes continue with P0240 (range/performance), P0241 (low) and P0242 (high).

Should I turn up the boost to fix P0239?

No. OBD-Codes.com warns never to tighten the wastegate or modify a stock turbo engine to raise boost, because the fuel and timing won't adapt and engine damage can happen.

How much does it cost to fix P0239?

Neither source gives a repair cost. A loose clamp, wiring repair or sensor is usually far cheaper than a turbo, so get a diagnosis or written estimate before buying parts.

Sources

  1. OBD-Codes.com: P0239 Turbocharger Boost Sensor B Circuit Malfunction (Don Bowman, ASE Certified Automotive Tech)
  2. RepairPal: P0239 Turbocharger/Supercharger Boost Sensor "B" Circuit (rated Urgent)

Last reviewed 2026-10-26. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.