Fuel and air

P0033 — Turbo/Supercharger Bypass Valve 'A' Control Circuit Fault

Severity: medium Drive with care, to a shop

What P0033 means

The engine computer uses a bypass (recirculation) valve to release excess boost pressure, for example when the throttle closes. P0033 sets when the electrical signal in the control circuit of valve 'A' is outside the expected range, such as an open, a short or an out-of-range voltage. Boost control becomes inaccurate as a result.

Symptoms

  • Check Engine light on
  • Reduced power and sluggish acceleration
  • Low or no boost
  • Limp mode activation
  • Hissing or fluttering noise when lifting off the throttle

Possible causes

  1. Failed bypass valve or its solenoid actuator
  2. Open or shorted wiring, or corroded connector pins
  3. Vacuum leaks or damaged hoses at the valve actuator
  4. Faulty boost pressure sensor giving bad data
  5. Faulty turbo wastegate regulating valve
  6. ECM/boost controller failure (rare)

How to diagnose

  1. Scan all codes and freeze frame data, clear the code and see if it returns.
  2. Inspect the valve connector and harness for chafing, corrosion and bent pins.
  3. Check power and ground at the valve connector and test wire continuity to the ECM.
  4. Measure the valve coil resistance and compare it with the factory spec.
  5. Inspect vacuum lines and boost hoses for cracks and leaks.
  6. Command the valve with a scan tool active test and confirm it clicks and moves.
  7. Compare boost sensor readings with actual boost pressure.
  8. If everything checks out, test the ECM and look for software updates.

Common fixes

  • Replace the bypass valve or actuator
  • Repair the wiring or connector
  • Replace damaged vacuum hoses
  • Replace a faulty boost pressure sensor
  • Replace or reprogram the ECM (rare)

P0033 on different brands

Ford · manuals
Ford uses an extended P0033:16 code, meaning the control circuit voltage for valve 'A' is below the threshold, which identifies the specific monitor condition.

Questions and answers

What does code P0033 mean?

It is an electrical fault in the control circuit of turbo or supercharger bypass valve 'A'. The ECU sees a signal out of range and can't regulate boost accurately.

Can I drive with P0033?

Briefly and carefully, such as to a shop. Power is usually reduced, and extended driving with poor boost control can harm the turbo.

How do I fix P0033?

Start by inspecting the wiring, connector and vacuum hoses. If those are fine, test the bypass valve and replace it if needed.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.