P0034 OBD-II Trouble Code: Turbocharger or Supercharger Bypass Valve Control Circuit Low

Our certified mechanics come to you · Get a fair and transparent estimate upfront

EXCELLENT RATING ON

Cost of diagnosing the P0034 code

P0034 is a diagnostic trouble code (DTC) for "Turbocharger or Supercharger Bypass Valve Control Circuit Low". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic for $154.99 . Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $50.0 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

Cars Estimate* Credit towards follow-up repair Earliest Availability
Ford $154.99 $50.0
Toyota $154.99 $50.0
BMW $164.99 $50.0

*Estimates may vary by market

SCHEDULE P0034 DIAGNOSTIC Get a fair and transparent estimate upfront

P0034 trouble code definition

P0035 is the code for Turbocharger or Supercharger Bypass Valve Control Circuit Low

What the P0034 code means

Note that each manufacturer has a slightly different definition for this code as it is relative to their particular system. This usually means there is a problem with the bypass system for the turbocharger or supercharger to relieve intake air pressure, either completely or partially, depending on how the system is designed.

For this P0035 code, the boost pressure is too low for proper engine operation and power.

What causes the P0034 code?

A variety of things can cause the Check Engine Light to come on and an OBD-II scanner to indicate this P0034 code.

  • Sensor input voltage signals to the engine control module (ECM) that there is an indication of a boost level that is lower than 9 psi or as specified by the manufacturer which will cause a code to be stored and an Check Engine Light lamp to be illuminated. The ECM recognizes the data as an out of specification signal and prevents the ECM to properly control boost levels.

  • If the boost is less than 9 psi, it can indicate that pressure is not enough and the system possible has an intake air leak which prevents proper operation and power.

  • The turbo charger bypass valve be partially or completely open preventing any boost.

  • Intake air hoses, pipes, intercooler or clamps may be defective, damaged, or loose.

What are the symptoms of the P0034 code?

  • The ECM detects the bypass valve control circuit has a low current condition or open circuit.

  • The ECM cannot control the bypass valve for the turbo or supercharger.

  • The engine may have loss of power.

  • The Check Engine Light will come on once the ECM detects the failure.

How does a mechanic diagnose the P0034 code?

  • A mechanic will verify the code with an OBD-II scanner, then the mechanic should reset the code and road test the vehicle to determine if the Check Engine Light comes back on and if the P0034 code returns.

  • Depending on the manufacturer, a boost pressure test will need to be determined to see if the boost pressure is within the manufacturer's recommended range.

  • If the pressure is too low, a pressure test must be done to verify the pressure is low and out of manufacturer specification.

  • If the pressure is too low, then an inspection of the bypass valve should be done. The bypass valves are operated differently depending on the manufacturer. Some are spring operated and others, especially Asian models, are diaphragm operated with an electric sensor and control system.

Common mistakes when diagnosing the P0034 code

The most common mistake for this code is related to assuming basic components are operating normally.

  • The problem is usually related to intake leaks from cracked or damaged hoses, hose clamps loose or missing, or the bypass valve not functioning correctly to release pressure.

  • If the vehicle has an intercooler, that should be checked for leaks if the pressure gauge indicates low output.

  • Sometimes the boost pressure hose is off or leaking which prevents the valve from working.

  • Both the spring and diaphragm type valves must be checked as they can be cleaned or repaired with service kits.

  • It is also possible that the turbocharger or supercharger may be bad due to worn bearings, vanes, or is operating out of specification.

How serious is the P0034 code?

  • This code requires immediate attention and should be diagnosed as soon as possible.

  • The vehicle will still run but serious damage can occur to the engine if the problem is not repaired, especially if the pressure is too low. Engine damage, poor performance, and excessive fuel consumption may occur.

  • Often times, if the Check Engine Light came on immediately at start up, the OBD-II system can be reset and the vehicle will operate normally.

What repairs can fix the P0034 code?

The most common repairs to address the P0034 code are as follows:

  • Have a certified technician verify the code with a scanner, reset the fault codes, and perform a road test.

If the P0034 code returns, then follow the test procedure:

  • Do a pressure test on the intake system between the turbocharger and intake throttle valve. This will verify that the pressure is too low as specified by the manufacturer.

  • If the pressure is too low, check the intake hoses, pipes, intercooler and clamps for cracks, being loose or damaged. If they are correct, then check the bypass valve to determine if it is slightly or completely open allowing boost pressure to escape.

  • If the pressure is in the normal range as indicated by the manufacturer, the pressure sensor may be faulty.

I have found that this low pressure code P0035 is most commonly caused by intake hoses, pipes, and clamps not being tight and in good condition causing leaks in pressure. It is also possible that the intercooler may be damaged and leaking. Cracked hoses are hard to find and are usually not visible, as they are on the bottom of the hose in a low area which allows debris and fluids to collect, causing the hose to become brittle and crack which you can often not feel.

In one scenario, I’ve had to start the engine and check the hoses and intercooler by hand, just to to feel the air pressure coming out. Sometimes, the pressure under normal operation will blow off a hose completely causing a total loss of boost which is rather shocking when it happens.

Additional comments for consideration regarding the P0035 code

Many vehicles with mileage over 100,000 have momentary sensor problems that usually occur during start up or prolonged stress situations on the drive train.

If the Check Engine Light comes on and the vehicle seems to be operating normally, the OBD-II system can be reset using the scanner and the problem may not reoccur. This is why it is important to verify the fault and reset it before doing any repairs.

Need help with a P0035 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

Check Engine Light
P0034
trouble codes

No more waiting rooms! Our mechanics will come to you to diagnose and fix the P0034 code.

SCHEDULE P0034 DIAGNOSTIC
Get a $50 credit for the follow-up repair

Recent Check Engine Light is on Inspection reviews

Excellent Rating

(8600)

Rating Summary
8017
273
65
46
199
8017
273
65
46
199
 at YourMechanic

Brandon

9 years of experience
133 reviews
Brandon
9 years of experience
Ford Escort L4-2.0L - Check Engine Light is on - Nashville, Tennessee
Brandon showed up ahead of schedule, was very personable and diagnosed my problems. He also scheduled my next appointments which will be with him.
 at YourMechanic

William

23 years of experience
33 reviews
William
23 years of experience
Lexus IS250 V6-2.5L - Check Engine Light is on - Mableton, Georgia
Arrived early which was great. William was courteous, and attentive to the issue. Even though it took several attempts I'm so happy he was determined to fix it and he did!
 at YourMechanic

Dan

40 years of experience
1080 reviews
Dan
40 years of experience
Plymouth Grand Voyager - Check Engine Light is on - Lawrenceville, Georgia
Mr. Dan Barber was quite patient, courteous and quite knowledgeable. From my observation, Mr. Barber appears to be quite professional.
 at YourMechanic

Christopher

9 years of experience
120 reviews
Christopher
9 years of experience
Ford Fiesta L4-1.6L - Check Engine Light is on - Smyrna, Georgia
Chris communicated with us each step of the way up until his arrival. He listened well, was knowledgeable, and was prepared. He took the time to diagnose the problem, explained the what, why and how and provided a solution. I would definitely recommend him and will use him again.


More related articles

P2190 OBD-II Trouble Code: System Too Rich at Idle Bank 2
P2190 P2190 code definition System Too Rich at Idle Bank 2 What the P2190 code means This code indicates there is too much fuel in relation to air (air/fuel ratio) in bank 1 at idle only. Bank 1 is the...
P0374 OBD-II Trouble Code: Timing Reference High Resolution Signal A No Pulses
What What the P0374 code means The Powertrain Control Module (PCM) has discovered a problem in the high-resolution timing reference signal. What causes the P0374 code? There may be one or more causes for the P0374 code: A defective camshaft,...
P0454 OBD-II Trouble Code: Evaporative Emission Control System Pressure Sensor Intermittent
P0454 means there is an issue with the evaporative emission control system due to faulty fuel cap, solenoid, or broken hoses, canister, or vacuum.

Related questions

Having trouble trying to locate my knock sensor. It's throwing a code for it. 1,2,4,5,6 cylinder misfires
As you may know a knock sensor may fail for any of the following reasons: The knock sensor is faulty and needs to be replaced There is a wiring open/short/fault in the knock sensor circuit The PCM/ECM has failed Any...
Check engine light
Hello there, thanks for writing in. A failing coolant temperature sensor can have some subtle symptoms on your 2004 Toyota Camry. The coolant temperature sensor sends the signal to the coolant temp gauge, if the gauge reads wrong than the...
Cylinder 5 has a misfire.
Hi there. To determine if the injector is not working properly, either you can perform a cylinder cut out test on your injection system or you can swap your injector on cylinder number 5 with another cylinder and see if...

How can we help?

Our service team is available 7 days a week, Monday - Friday from 6 AM to 5 PM PST, Saturday - Sunday 7 AM - 4 PM PST.

1 (855) 347-2779 · hi@yourmechanic.com