P0034 code meaning
Turbocharger/Supercharger Bypass Valve A Control Circuit Low
Powertrain system Generic code P00xx codes Check engine light
What P0034 means
The turbocharger bypass valve A is the compressor recirculation (diverter) valve: it connects the pressure side of the compressor with the intake side upstream of the turbocharger. It opens when the throttle closes quickly at high boost, so the compressor does not surge and the compressor wheel keeps its speed for the next acceleration. It is not the wastegate, which bypasses exhaust gas around the turbine and has its own codes. The valve is either electric or a vacuum unit controlled by a solenoid. P0034 means the voltage at the control output is too low, typically because the control wire is shorted to ground; on some control modules an open circuit also sets this code.
P0034 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2 hours
- Clears after repairAfter a drive cycle
Symptoms of P0034
- Check engine light on
- Fluttering or hissing when lifting off the throttle if the valve stays closed
- Weak response after gear changes
- Too little boost if the valve stays open
Common causes of P0034
- Most likelyControl wire shorted to ground
- PossibleValve shorted internally
- PossibleSupply missing, e.g. fuse or main relay
- Less likelyOutput driver in the engine control module faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Turbocharger bypass valveTurbocharger bypass valve wiringEngine control module
What each part of P0034 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 0 | Area: fuel and air metering and auxiliary emission controls. |
| 34 | The exact fault in that area. |
What to do next
- Note P0034 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0034
What does P0034 mean?
P0034 means "Turbocharger/Supercharger Bypass Valve A Control Circuit Low". The turbocharger bypass valve A is the compressor recirculation (diverter) valve: it connects the pressure side of the compressor with the intake side upstream of the turbocharger. It is a generic code, so it means the same on every make.
Is it safe to drive with P0034?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P0034 fail an emissions test?
Yes, it can. P0034 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0034 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0034 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.