What Is OBD Code P0033?
Code P0033 stands for “Turbo/Supercharger Bypass Valve Control Circuit” and is triggered when your vehicle’s engine control module (ECM) detects a malfunction in the circuit that controls the turbocharger or supercharger’s bypass valve (also called a wastegate). This valve is responsible for regulating boost pressure by diverting excess exhaust gases away from the turbine when boost levels get too high. When the ECM can’t properly control this valve, it sets the P0033 code and illuminates your check engine light.
What Does P0033 Mean?
The P0033 code is a generic powertrain diagnostic trouble code that applies to turbocharged and supercharged vehicles. The bypass valve control circuit includes the wastegate solenoid, wiring harness, connectors, and the ECM driver that sends the control signal. When any component in this circuit fails or malfunctions, the ECM detects the electrical fault and stores the code.
This code doesn’t necessarily mean your turbo is damaged—it’s an electrical or control system problem rather than a mechanical failure of the turbocharger itself. However, if the bypass valve can’t be controlled properly, boost pressure may become unregulated, which can lead to engine damage if left unaddressed.
Common Symptoms of P0033
- Check Engine Light: The most obvious symptom; the CEL will illuminate on your dashboard
- Reduced Engine Power: The vehicle may enter limp mode to protect the engine, resulting in noticeably reduced acceleration and performance
- Turbo Boost Issues: Inconsistent or absent boost pressure; the turbo may not spool up properly
- Possible Overboost: If the bypass valve is stuck closed, excessive boost pressure may occur, causing rough running or engine knock
- Limp Mode: The transmission may shift harshly or the engine may be limited to lower RPMs as a safety measure
- Whistling or Hissing Sounds: Unusual turbo noises if the wastegate is not functioning correctly
- Poor Fuel Economy: Uncontrolled boost or limp mode operation can reduce efficiency
Possible Causes of P0033 (Ranked by Frequency)
- Wastegate Bypass Solenoid Failure (Most Common): The solenoid that controls the bypass valve can fail electrically or mechanically, preventing proper boost regulation. This is the #1 cause of P0033.
- Connector Corrosion: Corroded or oxidized connectors at the solenoid or ECM can break the electrical circuit, preventing the control signal from reaching the solenoid.
- Damaged Wiring Harness: Broken, pinched, or corroded wires in the bypass valve control circuit can interrupt the signal path.
- ECM Bypass Valve Driver Failure: The circuit inside the ECM that drives the solenoid signal may fail, preventing the module from sending any control signal.
- Cracked or Disconnected Vacuum Lines: If the bypass valve is vacuum-operated (common on many turbocharged vehicles), a cracked or loose vacuum hose will prevent proper valve operation.
- Faulty Bypass Valve Itself: The physical bypass valve may be stuck, damaged, or worn, though this is less common than solenoid failure.
- Poor Ground Connection: A weak or corroded ground wire can prevent the solenoid from completing its electrical circuit.
Diagnostic Steps for P0033
Step 1: Scan and Document the Code
Use an OBD-II scanner to confirm code P0033 and check for any related codes (such as P0032, P0034, or other boost control codes). Note the freeze frame data, which shows engine conditions when the code was set. Clear the code and test drive to see if it returns immediately or after a few drive cycles.
Step 2: Visual Inspection
Locate the wastegate solenoid (consult your vehicle’s service manual for its location). Inspect the solenoid connector for:
- Corrosion or green/white oxidation on the terminals
- Loose or damaged pins
- Water intrusion or moisture inside the connector
Also inspect the wiring harness for cuts, pinches, or abrasion damage. Check vacuum lines (if applicable) for cracks or loose connections.
Step 3: Clean Connectors
If corrosion is visible, disconnect the solenoid connector and clean the terminals with electrical contact cleaner and a small brush. Reconnect and test. Sometimes this simple step resolves the issue. If the connector is severely corroded, it may need replacement.
Step 4: Test Solenoid Resistance
Disconnect the solenoid and use a multimeter to measure its resistance. Most bypass solenoids should read between 5-15 ohms, but consult your vehicle’s service manual for the exact specification. If the reading is infinite (open circuit) or zero (short), the solenoid is faulty and needs replacement.
Step 5: Check Voltage at the Solenoid
With the solenoid connected and the engine running, use a multimeter to check for voltage at the solenoid connector. You should see a pulsing voltage signal (typically 12V). If there’s no voltage, the problem is in the wiring or ECM driver. If voltage is present but the solenoid doesn’t respond, the solenoid itself is likely bad.
Step 6: Inspect Vacuum Lines (If Applicable)
If your bypass valve is vacuum-operated, check all vacuum hoses for cracks, splits, or loose connections. Replace any damaged hoses. Ensure the hose is properly seated on both the solenoid and the bypass valve.
Step 7: Check Ground Connections
Trace the ground wire from the solenoid back to the engine block or chassis ground. Ensure the connection is clean and tight. A poor ground can prevent the solenoid from operating.
Step 8: Test Drive and Recheck
After making any repairs, clear the code and take the vehicle for a test drive. Monitor boost pressure if you have a boost gauge. The code should not return if the repair was successful.
Repair Cost Estimates
The cost to repair a P0033 code varies depending on the root cause:
- Connector Cleaning/Repair: $0–$100 (DIY) or $50–$150 (shop labor)
- Wastegate Solenoid Replacement: $150–$400 for parts + $100–$300 for labor = $250–$700 total
- Wiring Harness Repair/Replacement: $100–$500 depending on extent of damage and labor
- Vacuum Line Replacement: $20–$100 for parts + minimal labor
- ECM Reprogramming or Replacement: $500–$2,000+ (only if the ECM driver is faulty; rare)
Most P0033 repairs fall in the $250–$700 range, with solenoid replacement being the most common fix.
Can I Still Drive With Code P0033?
Severity: Moderate to High
You can technically drive a vehicle with code P0033, but it’s not recommended for extended periods. Here’s why:
- Limp Mode: Many vehicles enter limp mode when this code is detected, severely limiting power and acceleration. This makes highway driving unsafe and city driving sluggish.
- Overboost Risk: If the bypass valve is stuck closed, excessive boost pressure can damage the engine, potentially causing catastrophic failure.
- Engine Knock: Uncontrolled boost can cause detonation (engine knock), which damages pistons and bearings over time.
- Turbo Damage: While the turbo itself is usually fine, operating without proper boost control can accelerate wear on turbo components.
Recommendation: Have the code diagnosed and repaired as soon as possible. If you must drive the vehicle, avoid heavy acceleration and extended highway driving. If the vehicle enters limp mode, reduce speed and drive directly to a repair shop.
Frequently Asked Questions About P0033
Q: Can a bad battery cause code P0033?
A: Indirectly, yes. A weak or dying battery can cause low voltage at the solenoid, preventing it from operating properly. However, a truly bad battery would typically trigger other codes as well. If you suspect a battery issue, have it tested first before replacing the solenoid.
Q: Will code P0033 go away on its own?
A: No. P0033 is a fault code that requires diagnosis and repair. While the check engine light may turn off after a few drive cycles if the fault is intermittent, the underlying problem will remain and likely worsen. You should have the code properly diagnosed and fixed.
Q: Is the wastegate solenoid expensive to replace?
A: The solenoid itself typically costs $150–$400 depending on your vehicle make and model. Labor adds another $100–$300. Some vehicles have easily accessible solenoids (DIY-friendly), while others require significant disassembly. Check your vehicle’s service manual or consult a mechanic for a specific estimate.
Q: Can I drive with a cracked vacuum line causing P0033?
A: A cracked vacuum line is a simple fix (usually $20–$100 in parts), and you can drive carefully to a repair shop. However, the longer you drive with a vacuum leak, the worse the boost control issues become. Have it repaired promptly to avoid limp mode or engine damage from uncontrolled boost.
Q: What’s the difference between P0033 and P0032?
A: P0033 is a general bypass valve control circuit fault, while P0032 is specifically “Turbo/Supercharger Bypass Valve Control Circuit Low.” P0032 indicates the signal is too low or absent, while P0033 is a broader circuit malfunction code. Both require similar diagnostics and repairs.