P0239 Code Meaning and Next Steps

First checks take 10 to 20 minutes for the first checks. No special tools are usually needed for the first checks.

Can you keep driving?

Stop driving if any of these apply

!The engine starts stalling, losing power sharply, or refusing to respond to throttle normally.
!The check-engine light flashes or the vehicle suddenly runs much worse after the code appears.

If the light is steady and the vehicle still drives normally: Often yes for a short time, but it should not be ignored.

What to check first

Step-by-step checks

1
Free - no tools
Inspect the sensor connector, harness, and any small reference hose for damage or disconnection
2
Free - no tools
Check whether the code appeared after intake, turbo, or boost-line service
3
Basic tool needed
Compare the live reading with other engine behavior if scan data is available
4
Basic tool needed
If the vehicle has multiple boost sensors or control references, confirm which sensor path this code names
5
Basic tool needed
If other boost or pressure codes are present, diagnose the system together

If the code returns

-If the reading is unstable or implausible, sensor or wiring fault becomes more likely.
-If the hose path is wrong or leaking, fix that before replacing the sensor.
-If the code returns after repair, verify the reference and signal paths again.

Background

What this code means

P0239 is a generic OBD-II code for a turbocharger boost sensor B range or performance fault.

Some systems use a second boost reference or a secondary pressure signal, and when that reading does not behave correctly the ECU can no longer trust boost control fully.

Diagnosis

Common causes

Most common

Boost sensor B drift

The second pressure signal may no longer be believable.

Common

Connector or harness fault

A poor electrical connection can distort the signal.

Common

Reference hose issue

A split or blocked line can upset the secondary pressure reading.

Possible

Boost-control mismatch

The engine may be producing or reporting boost in a way the ECU does not expect.

Avoid these mistakes

What not to do

xDo not replace the sensor or pump first if there is obvious wiring, connector, or intake damage.
xDo not ignore drivability changes or stalling just because the code sounds electrical.

Parts

Parts that may need replacing

PartTypical costNotes

Boost sensor B$30-$150Relevant when the sensor output is clearly out of range.

Boost hose or line repair$10-$80Worth checking if the reference line is damaged or misrouted.

Connector repair$15-$90Useful if the plug or pins are damaged.

Related OBD codes

P0234

P0234 usually means the turbo or supercharger is producing too much boost.

P0235

P0235 usually means boost sensor A has a circuit malfunction.

P0236

P0236 usually means boost sensor A is out of range or performing poorly.

P0237

P0237 usually means boost sensor A is reading too low.

P0238

P0238 usually means boost sensor A is reading too high.

Source notes

Generic OBD-II (SAE J1979 / ISO 15031-5). P0239 was expanded around common secondary boost-sensor range/performance faults, including sensor drift, wiring issues, and reference-line problems.

This guide is written as a generic multi-make reference, so bulletin history, sensor locations, and repair order can still change by manufacturer and engine family.

This is generic OBD-II guidance and should not override vehicle-specific service information. Exact diagnosis and repair steps vary by make, engine family, and model year.

Last reviewed: 2026-04-10

Reference: Open reference

P0239 - P0239 Usually Means Boost Sensor B Is Out of Range or Performing Poorly