OBD-II Code P0035: Turbocharger/Supercharger Bypass Valve 'A' Control Circuit High

What Does P0035 Mean?

Your car's Powertrain Control Module (PCM) detected a high voltage on the turbocharger bypass valve control circuit. The computer cannot control the release of boost pressure, which damages your engine and turbocharger.

Technical definition: The PCM registered a voltage reading from the bypass valve's control circuit above the normal expected range. The PCM sees near battery voltage (12V) on the control line when it expects close to 0V (ground). This indicates a short to voltage, preventing valve control.

Can I Drive With P0035?

No — Do Not Drive. Driving with this code risks severe engine and turbocharger damage. The vehicle will likely enter a low-power 'limp mode' to protect the engine, creating a hazard in traffic. A failed bypass valve causes compressor surge, which destroys the turbocharger—a repair costing over $2,000.

Common Causes

• Damaged Wiring or Connectors (Very Common) — The primary culprit. The wiring harness to the bypass valve solenoid frays, melts from engine heat, or breaks internally from vibration (especially on Honda Civics). This creates a short circuit resulting in a high voltage signal.
• Faulty Bypass Valve Solenoid (Very Common) — The solenoid fails internally, gets stuck, or becomes contaminated with oil and dirt, preventing correct operation.
• Vacuum Leaks (Common) — Many bypass valves are vacuum-controlled. A cracked or disconnected vacuum hose prevents the valve from actuating, triggering circuit-related codes.
• Improperly Installed Aftermarket Parts (Less Common) — Incorrectly installed aftermarket blow-off valves or improper ECU tunes interfere with the bypass circuit.
• Blown Fuse (Less Common) — A blown fuse in a related system unexpectedly triggers a P0035 code on certain platforms.
• Faulty Boost Pressure Sensor (Less Common) — A bad sensor sends incorrect data to the PCM, falsely indicating a bypass valve problem.
• Failing Powertrain Control Module (PCM) (Rare) — A bad driver circuit inside the PCM sends the wrong voltage to the bypass valve. Consider this only after eliminating all other possibilities.

Symptoms

• Check Engine Light On — The first and most obvious sign of a circuit fault.
• Limp Mode and Reduced Power — The vehicle enters a self-protection 'limp mode,' severely limiting engine power and speed. Acceleration feels sluggish.
• Compressor Surge Noises — You will hear rattling, fluttering, or hissing sounds when letting off the gas pedal. This indicates damaging compressor surge.
• Black Exhaust Smoke — An improperly functioning bypass system creates a rich air/fuel mixture, causing black smoke under acceleration.
• Poor Fuel Economy (also visible on scanner) — Uncontrolled boost makes the engine run inefficiently, increasing fuel consumption.
• Rough Idle (also visible on scanner) — The engine runs unevenly at idle due to incorrect air management.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this code.

Common Fixes & Costs

• Repairing Damaged Wiring or Connectors — Parts: $10 - $30, Labor: $130 - $360, ~1.5 hr book time (Intermediate)
• Replacing the Turbocharger Bypass Valve Solenoid — Parts: $50 - $350, Labor: $80 - $150, ~0.8 hr book time (DIY)
  : OEM 36180-59B-005, 36181-5BF-A00 (Alt: Standard Motor Products, Dorman)
  : OEM BL3Z-9K378-A, FL3Z-9U465-A (Alt: Standard Motor Products (TBV1008))
  : OEM 55499323, 55574902 (Alt: Dorman)
• Replacing Cracked or Leaking Vacuum Hoses — Parts: $10 - $40, Labor: $40 - $80, ~0.5 hr book time (DIY)
• PCM Re-programming or Software Update — Parts: $0, Labor: $150 - $250, ~1 hr book time (Professional)
• Replacing the Powertrain Control Module (PCM) — Parts: $800 - $1,200, Labor: $150 - $250, ~1.5 hr book time (Professional)

DIY vs Professional

• Repairing Damaged Wiring or Connectors — Beginner: Maybe
  Tools: Multimeter, wire strippers, crimpers, heat shrink tubing.
• Replacing the Turbocharger Bypass Valve Solenoid — Beginner: Yes
  Tools: Basic socket set, ratchet, pliers.
• Replacing Cracked or Leaking Vacuum Hoses — Beginner: Yes
  Tools: Pliers, hose cutters.
• PCM Re-programming or Software Update — Beginner: No
  Tools: Manufacturer-specific diagnostic and flashing tools.
• Replacing the Powertrain Control Module (PCM) — Beginner: No
  Tools: Advanced scan tools, socket set.

Used vs. New Parts: Buying Guide

When a used part is worth it: A used OEM bypass valve solenoid from a low-mileage vehicle is a cost-effective alternative to a new aftermarket part.

Donor-vehicle mileage cap: roughly under 80000 miles for the part to have meaningful remaining life.

Donor quality checklist:

• Verify the donor vehicle was not scrapped due to turbo-related failure.
• Inspect the electrical connector for corrosion or damage.
• Match the OEM part number exactly.

Decision logic:

• If The vehicle is less than 8 years old and the new OEM part costs less than $200 → Buy a new OEM part for maximum reliability.
• If The vehicle is older, and budget is the primary concern → A used OEM part or a new aftermarket part are acceptable options.
• If The specific part has a known high failure rate → Favor a new, revised part to avoid repeating the inherent flaw.

Warranty tradeoff: Used parts typically come with a 30-90 day warranty. New aftermarket parts offer a 1-year to limited lifetime warranty. New OEM parts carry a 1-year/12,000-mile warranty.

Worst-case if a used part fails: $150 - $300 if a cheap part fails shortly after installation, requiring repeat labor.

What Happens If You Wait — Timeline

1. 0-1 week: Check Engine Light illuminates. Vehicle enters 'limp mode' intermittently upon aggressive acceleration. (MPG impact: 0-5%% · Added cost: $0)
2. 1 week - 2 months: Limp mode becomes frequent. Fuel economy drops. A fluttering noise (compressor surge) occurs when letting off the gas pedal. (MPG impact: 5-15%% · Added cost: $50-150 in wasted fuel.)
3. 2-6 months: Compressor surge places severe stress on the turbocharger's internal bearings. The engine runs rich, fouling spark plugs. (MPG impact: 10-20%% · Added cost: $250+ (Diagnostic fees, spark plug replacement, wasted fuel).)
4. 6+ months: Catastrophic turbocharger failure occurs. The compressor wheel shatters, sending metal fragments into the intercooler and engine. (MPG impact: 15-25%% · Added cost: $2,000 - $4,000+ for turbocharger replacement and related labor.)

Cost of Not Fixing It

• 0-1 month: Noticeable drop in fuel economy (5-15%), poor acceleration, and activation of 'limp mode'. (Added cost: Negligible, other than increased fuel costs.)
• 1-6 months: Risk of catastrophic turbocharger failure due to compressor surge. Uncontrolled pressure reversals place extreme stress on the turbo's bearings. (Added cost: $2,000 - $3,000+ for turbocharger replacement.)
• 6+ months: Further engine damage. An incorrect air/fuel mixture fouls spark plugs and damages internal engine components. (Added cost: $3,000 - $7,000+ depending on the extent of engine damage.)

Diagnosis Steps

1. Read the Code and Freeze Frame Data
   Use an OBD-II scanner to confirm P0035. Analyze the freeze frame data to see the engine's state when the code triggered. Note any other codes present.
   Tools: OBD-II Scanner (Beginner)
2. Check for Technical Service Bulletins (TSBs)
   Check for TSBs related to P0035 for your specific vehicle. For example, Honda issued a campaign for the 2017 Civic Type R to replace the engine harness for this exact code.
   Tools: Online Repair Database (Beginner)
3. Visual Inspection & 'Wiggle Test'
   Inspect the bypass valve, electrical connector, and wiring. With the engine running, gently wiggle the wiring harness. If the engine sound changes, you found an intermittent short or break.
   Tools: Flashlight, Hands (Beginner)
4. Test the Bypass Valve Solenoid Circuit Voltage
   With the ignition on and engine off, disconnect the bypass valve connector. Use a multimeter to check for voltage. Finding battery voltage on the control wire indicates a short to power.
   Tools: Multimeter (Intermediate)
5. Test the Solenoid's Resistance
   Measure the electrical resistance across the solenoid's two pins. A typical range is 20-40 Ω. A reading of infinity (OL) or near zero means the solenoid is bad.
   Tools: Multimeter (Intermediate)
6. Command the Solenoid with a Bi-Directional Scanner
   Command the bypass valve solenoid to open and close. You should hear an audible click. If the PCM sends the command but voltage doesn't drop to near 0V, the issue is in the wiring or PCM.
   Tools: Bi-Directional Scan Tool (Advanced)
7. Check Live Data PIDs
   Monitor live data PIDs like 'Bypass Valve Commanded State'. If the commanded state changes but the circuit voltage PID remains high, it confirms a circuit fault.
   Tools: Advanced OBD-II Scanner (Advanced)
8. Check for a Short to Voltage in the Harness
   Disconnect the PCM and solenoid. Check for continuity between the control wire pin at the PCM connector and a 12V power source. Continuity confirms a shorted wire.
   Tools: Multimeter, Wiring Diagram (Advanced)

When This Code Triggers (Freeze-Frame Conditions)

• Engine Coolant Temp: 180-210°F (The engine is at full operating temperature.)
• RPM: 2000-4000 RPM (During acceleration or when demanding boost.)
• Engine Load: 40-80% (Under moderate to heavy load as the PCM attempts to control boost pressure.)
• Vehicle Speed: 40-65 mph (During highway driving or merging when the turbo is active.)

Related Codes

• P0034 — Indicates 'Control Circuit Low.' It is the direct opposite of P0035, pointing to a lack of voltage (open circuit or short to ground) rather than excess voltage.
• P0033 — Indicates 'Control Circuit Open.' Specifically points to a broken wire, an unplugged connector, or a completely failed solenoid.
• P0234 — Indicates 'Engine Overboost Condition.' Appears alongside P0035 because the circuit high fault prevents the bypass valve from opening, creating too much pressure.
• P0299 — Indicates 'Engine Underboost Condition.' Appears with P0035 if the valve is stuck partially open due to the electrical fault, causing a constant boost leak.

Climate & Environmental Factors

• Humidity and Road Salt: Moisture penetrates connectors and wiring insulation, leading to shorts and high resistance that trigger P0035. Applying dielectric grease prevents this.
• Extreme Heat: Wiring routed near the hot turbocharger breaks down faster. High ambient temperatures make insulation brittle and prone to melting, causing a short to voltage.
• Cold Weather: Extreme cold makes plastic connectors and vacuum lines brittle, increasing susceptibility to cracking during engine vibration.

How to Talk to a Mechanic About This Code

Say this: "I have a P0035 code, 'Turbocharger Bypass Valve Control Circuit High.' I'd like to book a diagnostic appointment. Based on my research, the most common causes are the solenoid or a wiring issue, so I'd like you to start by testing the circuit and the valve itself before looking at more expensive components."

This signals you are an informed customer. It directs the technician to the most likely and cost-effective starting points and discourages them from immediately quoting a costly turbocharger replacement.

Avoid saying:

• 'My turbo is broken.'
• 'My check engine light is on, can you just fix it?'
• 'I heard a noise, just replace whatever you think is wrong.'

Questions to ask before authorizing the repair:

• Did you test the voltage and resistance at the bypass valve connector? What were the readings?
• Did you inspect the wiring harness between the valve and the PCM for shorts or damage?
• Can you confirm the solenoid itself has failed before I authorize its replacement?
• What is the warranty on the parts and labor for this repair?

Where to Take It: Dealer vs Independent vs Chain

• Dealer: Recommended if your vehicle is under warranty or has a known, brand-specific problem documented in a TSB.
  Best for: Vehicles under warranty (powertrain or emissions)., Vehicles with known manufacturer-specific issues for this code (e.g., Honda Civic wiring TSBs)., Complex electrical diagnostics where factory tools are a benefit.
  Downsides: Highest labor rates., Prefers replacing an entire harness rather than performing a simpler wire repair. (Typical cost: +50% vs. baseline)
• Independent Shop: Best overall fit for most out-of-warranty vehicles, provided you choose a reputable shop with strong electrical skills.
  Best for: Out-of-warranty vehicles where cost is a factor., Shops with ASE-certified technicians specializing in electrical diagnostics.
  Downsides: Quality and diagnostic capability vary widely., Lacks access to the latest manufacturer software updates. (Typical cost: +0% vs. baseline)
• Chain Shop: AVOID for diagnosing P0035. The risk of misdiagnosis is high.
  Best for: Simple, unrelated maintenance like oil changes or tires.
  Downsides: Technicians lack the advanced electrical diagnostic experience needed for a 'Circuit High' fault., Incentivized to replace parts rather than perform detailed diagnostics. (Typical cost: -10% vs. baseline)

When to Walk Away From the Repair

If the estimated repair cost exceeds 50% of your car's private-party value, strongly consider selling or trading in the vehicle instead of repairing it. For older, high-mileage cars, use a lower threshold of 40%.

• Car worth $5000, fix is $400: Fix it. The repair cost is well below the 50% threshold.
• Car worth $8000, fix is $4500: Walk away. The repair costs more than half the car's value.
• Car worth $3000, fix is $1600: Borderline. The cost is over 50% of the car's value. Unless the car is otherwise in excellent condition, walk away.

What Scan Tool You Need for This Code

Minimum: A code reader that displays live data streams. You need to see the voltage on the bypass valve circuit to confirm the 'Circuit High' condition.

A basic $20 code reader only tells you the code exists. It cannot show the live electrical data that proves whether the fault is in the wiring, the solenoid, or the PCM.

Budget: BlueDriver Pro or MUCAR BT200 Max (~$70-120) — Connects to your smartphone to read codes, clear them, and display live data streams for the bypass valve circuit.

Mid-range: Innova 5610 or XTOOL D7 (~$250-400) — Adds bi-directional control, allowing you to command the bypass valve solenoid to open and close directly from the scanner.

Professional: Autel MaxiCOM MK808 / MX900 or Topdon Phoenix Lite (~$450-900) — Provides full bi-directional control, advanced live data graphing, and access to manufacturer-specific diagnostic procedures and wiring diagrams.

Rent vs buy: Auto parts stores read codes for free, but their tools lack live data or bi-directional control. If this is a one-time issue, pay a shop for a proper diagnostic. Buy a scanner only if you plan to do your own car repairs regularly.

How to Clear the Code After You Fix It

1. Use an OBD-II scan tool to clear the P0035 code.
2. Ensure the fuel tank is between 1/4 and 3/4 full.
3. Perform a complete drive cycle to allow readiness monitors to run.

Drive cycle (~30 minutes): After a cold start, idle for 2-3 minutes. Drive for 15-20 minutes with mixed city and highway speeds. Include steady driving at 55-60 mph for at least 5 minutes. Allow the vehicle to cool down completely.

Readiness monitors affected: Catalyst Monitor, Oxygen Sensor (O2) Monitor, Evaporative System Monitor

Watch out for:

• Disconnecting the battery clears the code but resets all readiness monitors to 'Not Ready', causing an automatic emissions test failure.
• The code returns immediately if the underlying electrical short is not repaired.

Will This Fail Emissions / State Inspection?

Yes — this code typically fails an OBD-II emissions inspection.

• California: An active P0035 code causes an automatic test failure. After repair, all readiness monitors must be set to 'Ready' before a retest.
• New York: An illuminated Check Engine Light and an active P0035 code result in an emissions test failure.
• Texas: In the 17 counties requiring emissions testing, a P0035 code prevents registration renewal.

Most Commonly Affected Vehicles

• Honda Civic (Si, Type R), CR-V, Accord (2016-2023) — Extremely common for the wire at the bypass valve connector to fatigue and break from engine vibration. The 2017 Civic Type R had a specific product update campaign (NHTSA ID: 10144933) for this issue.
• Ford F-150, Focus ST, Fiesta ST, Mustang EcoBoost (2013-2021) — Common on EcoBoost engines. Aftermarket blow-off valves are a frequent cause if not installed with the correct adapter.
• Chevrolet Cruze, Malibu, Equinox, Sonic (2016-2022) — Models with 1.4L and 1.5L turbo engines share a common bypass valve solenoid that is a frequent point of failure.
• Volkswagen/Audi GTI, Golf, Jetta, A3, A4 (2009-2019) — Failures of the diverter valve's diaphragm or the controlling N249 solenoid trigger P0035. Upgraded aftermarket valves are a common fix.
• Hyundai/Kia Genesis Coupe, Veloster Turbo, Forte, Optima (2010-2023) — The 2.0T and 1.6T engines experience this code due to electronic bypass solenoid or wiring issues.
• Buick Encore, Regal (2013-2022) — Shares the same 1.4L turbo engine and bypass valve design as the Chevrolet Cruze.
• GMC Terrain (2018-2022) — Equipped with the 1.5L turbo engine, known to have this code due to the shared GM bypass valve solenoid.
• Subaru WRX, Forester XT (2008-2021) — Triggered by a faulty bypass valve solenoid, but vacuum leaks in the complex hose system are a very common cause.

Manufacturer-Specific Notes

• Honda: On 10th and 11th generation Civic models, the wiring for the bypass valve solenoid breaks right at the connector due to engine vibration. This is the number one cause for P0035 on these cars.
• General Motors (Chevrolet, Buick, GMC): Models with 1.4L and 1.5L turbo engines use the same bypass valve solenoid, making it a common failure part across multiple vehicle lines. Replacement requires removing the turbo heat shield.
• Ford: On EcoBoost engines, installing an aftermarket blow-off valve without a proper electronic adapter triggers this code. The PCM expects a specific electrical load from the factory valve.
• Volkswagen / Audi: Referred to as a 'Diverter Valve'. Early versions used a rubber diaphragm prone to tearing. Later revisions use a durable piston-style valve.

Real Owner Stories

2018 Honda Civic Si with intermittent P0035

The check engine light and multiple warning lights appeared intermittently. The owner initially experienced no noticeable performance issues.

What they tried:

1. Replaced the wastegate actuator, but codes returned.
2. Replaced an O2 sensor, but codes returned after 30 minutes of driving.

Outcome: The owner discovered a common issue where the green wire to the bypass valve solenoid breaks internally from vibration. A 10-minute repair to cut and splice the broken wire permanently fixed the issue.

Lesson: On 10th/11th gen Honda Civics, the number one cause of P0035 is a broken wire at the bypass valve connector. Perform a 'wiggle test' before replacing parts.

2015 Ford F-150 2.7L EcoBoost after body shop repair

After front-end body work, the check engine light illuminated with code P0035.

What they tried:

1. Cleared the codes, but P0035 returned immediately.
2. Visually inspected wiring harnesses near the repair area.

Outcome: The owner found a broken wire in the harness near the front bumper, pinched where it makes a bend. Bypassing the broken section of wire resolved the code.

Lesson: If P0035 appears immediately after a front-end collision or repair, a wiring harness was pinched or a connector was left loose.

2017 Ford F-150 3.5L EcoBoost with aftermarket Blow-Off Valve (BOV)

After installing new turbos and a mechanical TurboSmart BOV, the truck continuously threw a P0035 code.

What they tried:

1. Verified turbo actuators were working.
2. Inspected the wire harness.

Outcome: Installing a mechanical BOV without the correct resistor in the factory electronic connector causes P0035. Installing a 100-ohm resistor simulated the factory valve's electrical load and fixed the issue.

Lesson: When installing an aftermarket BOV on an engine with a factory electronic bypass valve, you must use the correct electronic adapter or resistor.

How to Prevent This Code From Triggering

• Use high-quality full synthetic oil (Every oil change) — Turbochargers generate extreme heat. Full synthetic oil resists thermal breakdown and prevents 'coking' that seizes bearings and bypass valve mechanisms.
• Follow a stricter oil change interval (Every 5,000-7,500 miles) — Oil in turbocharged engines degrades faster. A shorter interval ensures the oil maintains protective properties.
• Protect wiring near the turbocharger (During any repair or inspection) — Wiring failure from heat is the primary cause of P0035. Add a high-temperature protective sleeve to the bypass valve harness to prevent melting.
• Apply dielectric grease to the connector (When replacing the valve or repairing the harness) — Dielectric grease keeps moisture and road salt out, preventing corrosion that causes high resistance or short circuits.
• Allow for a brief cool-down period (After hard driving) — Idling for 30-60 seconds allows circulating oil to carry away residual heat, preventing oil coking in the turbo's bearings.

Frequently Asked Questions

What does the turbo bypass valve actually do?

It acts as a pressure relief valve. When you take your foot off the gas, the throttle closes, but the turbo keeps spinning and creating pressure. The valve opens to recirculate this trapped pressure, preventing damaging compressor surge.

What are the most common mistakes when diagnosing P0035?

The most common mistake is replacing the bypass valve solenoid without testing the circuit. Technicians often find the actual problem is a broken wire or corroded connector. Always check wiring, connections, and TSBs before replacing expensive components.

Can aftermarket parts cause a P0035 code?

Yes. Installing an aftermarket blow-off valve (BOV) triggers a P0035 code if it lacks the correct electronic adapter for the PCM. Aggressive engine tunes that alter boost parameters also cause the system to operate outside expected ranges.

Is it safe to drive with a P0035 code?

No. Your car will suddenly lose power or enter 'limp mode,' creating a hazard in traffic. Continuing to drive risks severe turbocharger damage from compressor surge, costing thousands to fix.

What is 'limp mode'?

Limp mode is a safety feature where the car's computer drastically reduces engine power and speed. It activates to protect the engine from catastrophic damage when a serious fault like P0035 occurs.

Can I fix P0035 myself?

A DIY fix is possible for accessible vacuum hoses or simple connector wiring repairs. However, diagnosing electrical shorts within the main harness requires a multimeter and wiring diagrams. If you lack electrical diagnostic experience, take it to a professional.

How much does it cost to fix P0035?

A diagnostic fee runs $100-$180. Simple wiring or vacuum hose repairs cost $150-$300. Replacing the bypass valve solenoid costs $230-$500, while a full PCM replacement exceeds $1,200.

Can a weak battery cause a P0035 code?

No. A weak battery causes low voltage issues, whereas P0035 specifically indicates a 'Circuit High' (excess voltage) condition. The root cause is almost always a short to power within the bypass valve circuit itself.

Key Takeaways

• Code P0035 indicates a high-voltage short in the turbocharger bypass valve circuit, preventing the computer from safely releasing boost pressure.
• Do not drive with this code; it causes damaging compressor surge that destroys turbochargers, leading to repair bills exceeding $2,000.
• The most common fix is repairing a broken or melted wire at the bypass valve connector, which costs between $130 and $360 at a repair shop.
• On 2016-2023 Honda Civics, a broken green wire at the bypass valve connector is the number one cause, easily diagnosed with a simple engine-running wiggle test.