DTC P0033 — Turbocharger Bypass Valve Control Circuit.

✅ DTC P0033 — Turbocharger Bypass Valve Control Circuit (Turbocharger/Supercharger BOV/CBV)

This code means the ECM detected an electrical fault in the circuit that controls the turbo bypass valve (also called blow-off valve (BOV) or compressor bypass valve (CBV)).

It is not a boost leak code, but an electrical circuit issue.

🔧 Common Causes

1. Fault in Bypass Valve Control Solenoid

Internal short/open

Stuck solenoid

2. Wiring Problems

Damaged harness

Corrosion at connectors

Loose pins

Short to ground / short to power

3. Boost Control/Bypass Valve Vacuum Issues

(If vacuum-controlled type)

Leaky vacuum line

Bad vacuum actuator

4. ECM Driver Fault (less common)

Output driver for the valve failed

🔍 Symptoms

Low boost or overboost

Turbo flutter noise

Reduced power

Engine light on

Sometimes rough acceleration

🧰 Step-by-Step Diagnostic Procedure

1. Visual Inspection

Locate the turbo bypass valve

Inspect wiring from:

Bypass valve → Control solenoid → ECM

Check for:

Oil contamination

Melted insulation

Loose connectors

Broken pins

If harness is OK → Move to step 2

2. Test the Bypass Valve Solenoid (Electrical Check)

Using multimeter:

A. Check resistance

Disconnect solenoid

Measure coil resistance (compare to manufacturer specs — typically 20–40 Ω)

If OL (open) or very low (<5 Ω): Replace solenoid

B. Check power supply

One wire should have 12V with ignition ON

Other wire is ECM control (ground pulse)

If NO 12V:

Check fuse

Check for open circuit in power feed

3. Check ECM Control Signal

Backprobe ECM control wire

Use a test light or scope

Should see pulsed ground during acceleration

If there is no control signal:

Possible:

Broken wire from ECM to solenoid

Bad ECM driver (rare)

4. Test Vacuum System (if vacuum-type valve)

Check vacuum lines for leaks

Test actuator with a hand vacuum pump

Should hold vacuum and move smoothly

If actuator does not hold vacuum → Replace actuator

5. Turbocharger Inspection

(Only if all electrical checks pass)

Check bypass valve diaphragm

Check for sticking valve

Check boost leaks

🛠️ Most Common Fixes

✔ Replace turbo bypass valve solenoid
✔ Repair wiring harness (most common cause)
✔ Replace vacuum hose
✔ Clean connectors & remove corrosion
✔ Replace bypass valve/actuator
✔ ECM replacement (very rare)

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