Faulty bypass valve solenoid or electric actuator (internal open or short circuit); Damaged, chafed or corroded wiring between the valve and the control unit; Loose, corroded or contaminated connector at the valve or control unit; Blown fuse or fault in the power or earth supply to the valve; Bypass valve stuck or damaged mechanically, loading the circuit or causing a feedback mismatch (depends on valve design); Fault in the engine control unit driver circuit; Outdated control unit software that wrongly sets the fault (only where the manufacturer has documented this for the engine).

P0033

Turbocharger/Supercharger Bypass Valve A Control Circuit.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
0: AreaFuel and air metering, auxiliary emission controls
33: FaultThe specific fault in that area

What it means

P0033 is the generic SAE J2012 code for a fault in the control circuit of turbocharger or supercharger bypass valve A. This valve (often called a recirculation, blow-off or diverter valve) is operated by the engine control unit, and the code sets when the commanded state of the circuit does not match what the control unit measures. That points to an electrical problem such as an open circuit, short or a failed solenoid, rather than a mechanical fault.

Symptoms

Engine warning light on
Loss of power or boost, possibly with the engine in limp mode
Hissing or fluttering noise from the intake when lifting off the throttle
Hesitation or surging under acceleration
Whistling or air leak noises under boost
Poor fuel economy

Possible causes

Faulty bypass valve solenoid or electric actuator (internal open or short circuit)likely
Damaged, chafed or corroded wiring between the valve and the control unitlikely
Loose, corroded or contaminated connector at the valve or control unitlikely
Blown fuse or fault in the power or earth supply to the valvepossible
Bypass valve stuck or damaged mechanically, loading the circuit or causing a feedback mismatch (depends on valve design)possible
Fault in the engine control unit driver circuitrare
Outdated control unit software that wrongly sets the fault (only where the manufacturer has documented this for the engine)rare

How to diagnose

Read all stored and pending codes and note the freeze frame data (engine load, speed, temperature) to see when the fault set
Look for other boost, turbo or vacuum related codes that might point to a shared cause
Visually inspect the valve, its connector, the wiring harness and the nearby vacuum or air pipes for damage, heat damage, chafing, oil or loose fittings
Check the relevant fuse and the power and earth supply at the valve connector using the wiring diagram for the vehicle
Measure the valve solenoid or actuator resistance and compare it with the manufacturer specification
Using a scan tool with active tests, command the valve and listen for or feel it operating, and watch the commanded and actual values
Check the wiring between the valve and control unit for continuity, short to earth and short to supply
Check the valve moves freely and seals properly, and check for any applicable software updates for the model and engine

How to fix

Replace the bypass valve or its solenoid or actuator if it fails electrical or operating tests
Repair or replace damaged wiring and secure any loose or chafed harness sections
Clean or renew corroded or damaged connectors and terminals
Replace the blown fuse after finding and correcting the reason it failed
Renew a sticking or damaged mechanical valve assembly, including any worn diaphragm or seals
Update the control unit software only if the manufacturer lists it as the fix for a confirmed fault, or repair or replace the control unit if its driver circuit is confirmed faulty

Can I keep driving?

Medium severity

The car can usually be driven short distances, but expect reduced power and possible limp mode. Get it checked soon, as a faulty bypass valve can stress the turbocharger and affect drivability.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.