P0035 is a trouble code you usually see on turbocharged or supercharged engines, and it points straight at the boost control system. When this code sets, your engine computer is telling you the turbo/supercharger bypass valve control circuit is out of its normal range. That can mean an electrical problem, a sticking bypass valve, or even wiring damage. If you’ve noticed low power, odd turbo noises, or the check engine light after some boost-related issues, this guide will walk you through what P0035 means, how serious it is, and what you can do to fix it.
What Does P0035 Mean?
DTC P0035 stands for “Turbocharger Bypass Valve Control Circuit High.” In plain language, your ECU is seeing higher-than-expected voltage in the circuit that controls the turbo (or supercharger) bypass valve, sometimes also called the boost control solenoid or diverter valve.
This valve controls how much boost pressure the engine actually sees. If the circuit is “high,” the ECU thinks the valve control line is over-volted or stuck in one state. That can lead to incorrect boost levels, limp mode, or drivability issues. The problem can be in the valve itself, the wiring, the connector, or less commonly the ECU driver.
Quick Reference
- Code: P0035 – Turbocharger Bypass Valve Control Circuit High
- Severity: Moderate to high (boost and drivability issues)
- Common Causes: Bad bypass valve/solenoid, wiring fault, poor connection
- Typical Symptoms: Low power, overboost/underboost, check engine light
- Systems Affected: Turbo/supercharger control, engine performance
Real-World Example / Field Notes
In the shop, I most often see P0035 on turbocharged gas engines after someone has been chasing a boost problem or adding aftermarket parts. A common scenario: a customer installs a blow-off valve or boost controller, then the car suddenly feels sluggish and the check engine light comes on with P0035. Testing usually shows the bypass valve solenoid stuck or the wiring pulled tight and partially broken. Once the damaged harness section is repaired or the solenoid replaced with the correct OEM part, boost control comes back to normal and the code stays away.
Symptoms of P0035
- Check engine light illuminated, sometimes with reduced power or limp mode
- Low power / poor acceleration, especially when you expect boost to kick in
- Erratic boost, surging or fluctuating power under hard throttle
- Unusual turbo noises such as whooshing, flutter, or hissing under load
- Overboost or underboost conditions, sometimes with additional boost-related codes
- Worse fuel economy due to incorrect boost and fueling strategy
- Harsh or hesitant shifting on automatic transmissions that rely on torque data
Common Causes of P0035
Most Common Causes
- Faulty turbocharger bypass valve / boost control solenoid (internal short or stuck plunger)
- Open or shorted wiring in the bypass valve control circuit (rubbed-through or melted wires)
- Corroded, loose, or damaged electrical connector at the bypass valve
- Aftermarket modifications (blow-off valve, tune, boost controller) installed or wired incorrectly
- Vacuum line issues on vacuum-operated bypass valves (leaks, splits, or disconnected hoses)
Less Common Causes
- Faulty ECU/PCM driver for the bypass valve circuit (internal failure)
- Poor engine or chassis ground causing abnormal circuit voltage
- Short to voltage from another circuit in the harness (improper repairs or collision damage)
- Water intrusion into harness or connectors near the turbocharger
- Previous incorrect repair, such as bypassing the solenoid or splicing wrong wires together
Diagnosis: Step-by-Step Guide
You’ll want a basic scan tool (preferably one that can read live data), a digital multimeter, and if possible a wiring diagram for your specific vehicle. A handheld vacuum pump helps on systems that use vacuum-operated bypass valves. Good lighting and access to the turbo area are important, as the components often sit near hot exhaust parts.
- Confirm the code and check for companions. Use a scan tool to verify P0035 is present. Look for related boost codes (P0234, P0299, etc.) and note freeze-frame data (engine load, RPM, boost) when the code set.
- Perform a visual inspection. Locate the turbo bypass valve/solenoid and follow its wiring. Look for melted insulation, rubbed-through spots on brackets, broken connectors, or loose pins. Repair any obvious issues first.
- Check the connector condition. Unplug the bypass valve connector and inspect for corrosion, bent pins, moisture, or oil contamination. Clean or replace the connector as needed and ensure it clicks firmly when reconnected.
- Test the solenoid resistance. With the connector unplugged and key off, measure the resistance across the solenoid terminals using a multimeter. Compare to spec in service data. Very high, very low, or infinite resistance indicates a bad solenoid.
- Verify power and ground at the valve. With key on, use the multimeter to check for proper supply voltage and ground at the connector. A missing power or ground points you toward a wiring or fuse/relay issue.
- Check for short to voltage. If the ECU is reporting “circuit high,” look for a wire in the control circuit that may be touching battery voltage. Backprobe the control wire and watch voltage while wiggling the harness; spikes suggest an intermittent short.
- Command the valve with a scan tool. On many vehicles, you can use bi-directional controls to command the bypass valve on/off. Listen and feel for it clicking, and watch live data (boost pressure) to see if it responds as expected.
- Inspect vacuum lines (if equipped). For vacuum-operated valves, check all hoses for cracks, splits, or disconnections, especially near hot components. Replace any suspect lines and verify proper routing.
- Check ECU outputs (advanced). If wiring and the solenoid test good but P0035 persists, you may need to check the ECU driver with a lab scope or follow OEM test procedures. At this point, most DIYers are better off at a qualified shop.
Pro tip: Always clear the code and perform a proper road test under boost conditions after any repair. Watch live data for boost pressure, commanded vs. actual, and see if P0035 or related codes return before calling the fix complete.
Possible Fixes & Repair Costs
Fixing P0035 usually means repairing the electrical side of the bypass valve circuit or replacing the valve/solenoid itself. Common repairs include replacing the turbo bypass valve, repairing or replacing damaged wiring, cleaning or replacing corroded connectors, or correcting poorly installed aftermarket components. Typical repair costs at a shop range from about $150–$350 for wiring or connector repairs and $250–$700 for bypass valve or solenoid replacement, depending on parts prices, labor time, and how buried the turbo components are. ECU replacement or reprogramming, while rare, can push costs much higher.
- Replace turbo bypass valve / boost control solenoid
- Repair or replace damaged wiring harness sections
- Clean, tighten, or replace corroded connectors
- Re-route or secure wiring away from hot exhaust components
- Correct or remove improper aftermarket boost-related modifications
- Replace cracked or leaking vacuum hoses (if used by the system)
- Reflash or replace ECU/PCM only if confirmed faulty
Can I Still Drive With P0035?
In many cases you can still drive with P0035, but it’s not something to ignore for long. Some vehicles will default to low boost or limp mode to protect the engine, so you’ll notice reduced power. Others may allow partial or inconsistent boost, which can make the car unpredictable. If you hear loud turbo noises, feel severe power loss, or see additional warning lights, it’s best to park the vehicle and have it checked. Continued hard driving with a boost control issue can stress the engine and turbocharger.
What Happens If You Ignore P0035?
Ignoring P0035 can lead to long-term problems. Incorrect boost control can cause excessive turbo speed, high intake temperatures, and lean or rich conditions under load. Over time that can damage pistons, head gaskets, catalytic converters, and the turbo itself. You may also end up with poor fuel economy and fail an emissions test. Fixing the issue early is usually cheaper than dealing with the fallout from extended driving with faulty boost control.
Related Codes
- P0027 – Exhaust Valve Control Solenoid Circuit Range/Performance Bank 1
- P0026 – Intake Valve Control Solenoid Circuit Range/Performance Bank 1
- P0019 – Crankshaft Position Camshaft Position Correlation Bank 2 Sensor B
- P0018 – Crankshaft Position Camshaft Position Correlation Bank 2 Sensor A
- P0017 – Crankshaft Position Camshaft Position Correlation Bank 1 Sensor B
- P0016 – Crankshaft Position Camshaft Position Correlation Bank 1 Sensor A
- P0009 – Engine Position System Performance Bank 2
- P0008 – Engine Position System Performance Bank 1
- P0007 – Fuel Shutoff Valve “A” Control Circuit High
- P0006 – Fuel Shutoff Valve “A” Control Circuit Low
Key Takeaways
- P0035 means the ECU sees a high-voltage fault in the turbo/supercharger bypass valve control circuit.
- Symptoms usually include a check engine light, low or erratic boost, and reduced performance.
- Most causes are electrical: bad solenoid, damaged wiring, or poor connections near the turbo.
- Diagnosis involves visual inspection, resistance tests, power/ground checks, and scan tool commands.
- Typical repairs run from about $150 to $700 in most cases, depending on parts and labor.
- Driving short-term may be possible, but ignoring P0035 can eventually damage the engine or turbo.
Vehicles Commonly Affected by P0035
P0035 shows up most often on turbocharged gasoline engines. You’ll commonly see it on Ford EcoBoost models (F-150, Escape, Fusion), GM turbo vehicles (Chevy Cruze, Sonic, Malibu, Buick Regal), Volkswagen and Audi 1.8T/2.0T engines, Subaru WRX and Forester XT, Hyundai and Kia 1.6T/2.0T engines, and various Mercedes-Benz and BMW turbo models. It can also appear on aftermarket-turbo setups or supercharged applications where the bypass valve and wiring are close to heat and vibration.
FAQ
Can I clear P0035 and keep driving if the car feels normal?
You can clear the code and see if it returns, but if the underlying fault is still there, P0035 will usually come back quickly under boost. Even if the car feels normal now, intermittent wiring or solenoid issues tend to get worse over time, so plan on diagnosing and repairing it rather than just clearing the light.
Is P0035 the same as an overboost code?
No. P0035 is an electrical circuit code for the bypass valve control, while overboost codes like P0234 are based on actual boost pressure readings. However, a faulty bypass valve circuit can cause overboost or underboost, so you may see P0035 along with boost pressure codes.
How serious is P0035 for my engine?
P0035 is moderately serious. It may not cause immediate engine damage, but incorrect boost control can stress internal components, raise exhaust temperatures, and damage the turbo if ignored. Treat it as a problem you should diagnose and repair soon, not something to live with indefinitely.
Can a bad tune or aftermarket blow-off valve cause P0035?
Yes. Poorly calibrated tunes, incorrectly wired boost controllers, or non-OEM blow-off/bypass valves can confuse the ECU and upset the bypass valve circuit. If P0035 started right after modifications, inspect that work first and consider reverting to stock components or a proper professional tune.
Can low battery voltage or charging problems trigger P0035?
It’s less common, but overall electrical issues can contribute. A weak battery or charging system can cause erratic voltages and strange sensor readings. If you see multiple unrelated electrical codes along with P0035, it’s worth checking battery health, alternator output, and main grounds in addition to the bypass valve circuit.