P0033 — Turbocharger/Supercharger Bypass Valve A Control Circuit

The fault concerns bypass valve A control, used to divert or recirculate charge air according to design. It does not automatically identify the exhaust wastegate.

Affected system: Powertrain

Symptoms

• Engine warning lamp; limited power or weak acceleration.
• Irregular boost response; sometimes only a stored code without clear symptoms.

Possible causes

• Connector damage or wiring affected by heat, chafing or vibration.
• Actuator/solenoid electrical fault; investigate the driver only after circuit checks.

What to check

• Identify bypass valve A in engine documentation and read the full subcode; A alone does not identify its location.
• Save failure data and related pressure/position codes; determine whether the fault is constant or command-dependent.
• Inspect the hot-area connector, harness supports and heat damage; check the specified supply and ground.
• Measure supply and circuit integrity using the wiring diagram; boost pressure does not test electrical continuity.
• Verify operation after repair by the OEM method; rod adjustment or turbo replacement does not replace circuit diagnosis.

Also written as: P0033-00, P003300, PO033 (some scan tools add the fault-type byte, e.g. -00).