P0039

Turbocharger/Supercharger Bypass Valve A Control Circuit Range/Performance

Q: Is it safe to drive with P0039?

For short trips usually yes, but expect reduced power. Boost control faults can trigger limp mode, so get it fixed before hard driving or towing.

Q: Can I just clear P0039?

You can, but it will come back within a few drive cycles unless the valve, wiring, or connection causing it is actually repaired.

Turbo / boost control Generic OBD-II High

What it means

P0039 means the engine computer sees the turbo (or supercharger) bypass valve control circuit behaving outside its expected range — the valve isn't responding the way the ECM commands. It won't strand you, but boost can become erratic and the car may fall into a reduced-power mode until the valve, wiring, or connection is repaired.

High

Can I keep driving? Usually drivable, but the car may drop into a reduced-power limp mode and feel sluggish under boost until it's fixed.

Real-world scan data

Seen in

148

scans in the past year

Found in

<0.1%

of scans

<0.1%

of scans that found faults

Appears alongside · share of P0039 scans

P0645in 65.5% of scans

P2B93in 60.1% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Check-engine light on
Reduced power or sluggish acceleration, sometimes with limp mode
Erratic or inconsistent boost pressure
Whining or hissing noise from the intake under boost
Slightly reduced fuel economy

Common causes

Most likely first

Failed or sticking turbo bypass (recirculation/diverter) valveLikely
Damaged wiring or connector at the bypass valveCommon
Loose or corroded electrical connections in the control circuitCommon
Boost/vacuum leak affecting how the valve respondsLess often
Failed engine control module (ECM) — rareLess often

How to diagnose & fix

Work through it in order

Read freeze-frame data and check for other boost-control codes to narrow it down.
Inspect the bypass valve connector and wiring for damage, looseness, or corrosion.
Test the bypass valve for correct operation and resistance; replace it if it sticks or reads out of spec.
Check the intake and boost plumbing for leaks that could skew valve response.
If wiring and valve are good, consider the ECM last. Clear and re-test.

FAQ

Quick answers

Is it safe to drive with P0039?+

For short trips usually yes, but expect reduced power. Boost control faults can trigger limp mode, so get it fixed before hard driving or towing.

Can I just clear P0039?+

You can, but it will come back within a few drive cycles unless the valve, wiring, or connection causing it is actually repaired.

Read & clear P0039 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX