Fix P0035: Mechanic’s solutions that WORKED

The P0035 indicates an issue with the turbocharger bypass valve control circuit, specifically that the circuit has a high output. This valve, crucial in turbocharged engines, helps regulate the turbo’s boost pressure by redirecting excess air, ensuring the engine runs smoothly under varying loads and speeds. A high circuit signal can suggest electrical problems, affecting the turbo’s performance and potentially leading to engine damage if not addressed.

P0035 quick overview

Meaning	P0035 – Turbocharger Bypass Valve Control Circuit High
Is it serious?	Yes, it can significantly impact engine performance and fuel efficiency.
Possible causes	– Faulty turbocharger bypass valve – Wiring or connector issues in the bypass valve circuit – Problems with the vehicle’s ECM (Engine Control Module)
How to diagnose?	Inspect the turbocharger bypass valve for damage or malfunction. Check the wiring and connectors for breaks, shorts, or corrosion. Use a diagnostic scanner to test the solenoid’s functionality and monitor ECM commands. Verify the valve’s resistance to ensure it matches manufacturer specifications. Examine the ECM for any signs of failure or issues with the control circuit.

How to fix P0035 – learn from mechanics

I looked into P0035 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Ford

Vehicle Information 2011 Ford F-150 FX4 3.5L

Issue + Repair History

• MIL lamp on with DTC: P0035 – Turbocharger Bypass Valve Control Circuit High.
• Replaced switching valve on top of the manifold controlling vacuum to turbos but issue persisted.

Other OBD2 Codes + Test Results

• DTC:
  • P0035: Turbocharger Bypass Valve.
• No additional test results mentioned.

Mechanic Suggestions

• Use scanner to turn the solenoid on and off to check functionality.
• Investigate ground side command from the computer.
• Check for high voltage when the valve is commanded on, indicating a problem with the control or return side.
• Inspect for high or infinite resistance in the Turbocharger Bypass Valve circuit.
• Verify voltage at the Turbocharger Bypass Valve wire and proceed to check wiring if voltage is present.
• Check for voltage at the PCM and ground the circuit at the PCM KO to test wiring integrity.
• Examine wiring near the aftercooler above the outlet pipe to the throttle body.

Final Fix

• Replaced the valve located by the intercooler, resolving the issue.
• Verified no recurrence of the MIL lamp and cleared the DTC.
• Informed the customer of the repair completion.

Case #2: Volkswagen

Vehicle Information 2017 Volkswagen Golf GTI 2.0T

Issue + Repair History

• Customer reported a Check Engine Light (CEL) illuminated.
• Diagnostic Trouble Code (DTC): P0035 – Turbo Charger Bypass Valve Control Circuit High.
• Initial inspection revealed no visible issues with the turbocharger or bypass valve.
• Previous repair history: None related to turbocharger or bypass valve.

Other OBD2 Codes + Test Results

• DTC: P0035 – Turbo Charger Bypass Valve Control Circuit High.

Mechanic Suggestions

• Utilize a VW-specific diagnostic tool to access manufacturer-specific codes and data.
• Verify the integrity of the wiring harness connected to the turbocharger bypass valve.
• Test the turbocharger bypass valve for proper operation and resistance within specifications.
• Check for any vacuum leaks or obstructions in the bypass valve system.
• Inspect the electrical connections and wiring for signs of damage or corrosion.
• Ensure that the turbocharger wastegate is functioning correctly and not causing abnormal pressure buildup.

Final Fix

• Upon thorough inspection, a loose connection was found at the wiring harness connector to the turbocharger bypass valve.
• The connector was securely reattached, and the wiring harness was inspected for any signs of damage.
• The CEL was cleared, and the vehicle was road-tested to confirm that the issue was resolved.
• No further occurrences of the P0035 DTC were reported by the customer, indicating a successful repair.

Case #3: BMW

Vehicle Information 2002 BMW 325xi 2.5L

Issue + Repair History

• Customer presented with a Check Engine Light.
• DTC: P0035 – Turbo Charger Bypass Valve Control Circuit High.
• No turbocharger on the vehicle, leading to confusion over the code’s meaning.
• Further diagnosis revealed additional BMW-specific codes: 238 (misfire cylinder #1), 189 and 227 (primary O2 sensor), and 90, 91, 92 (body electrical codes).
• Codes cleared, and vehicle returned to customer pending further occurrences.

Other OBD2 Codes + Test Results

• DTC:
  • P0035: Turbo Charger Bypass Valve Control Circuit High.
  • Additional BMW-specific codes: 238, 189, 227, 90, 91, 92.

Mechanic Suggestions

• Use BMW-specific diagnostic software and connectors for accurate readings.
• Avoid throwing parts at the issue without proper diagnosis.
• Consider replacing the intake camshaft sensor with a dealer part to address potential issues.
• Verify the accuracy of the code interpretation with a better scanner.
• Beware of aftermarket parts’ reliability; opt for dealer parts for critical components.
• Check for an open circuit on bank 1 after the catalytic converter for the O2 sensor heater circuit.
• Consider intake and exhaust camshaft sensor replacement with dealer parts due to common failure.
• Investigate lean condition codes (e.g., 227) with fuel adaptations and smoke testing for air intake leaks.

Final Fix

• No final fix was provided as the issue had not recurred by the time of the forum update.
• Continued monitoring of the vehicle for further occurrences was advised.

Diagnostic Step	Explanation
Inspect the turbocharger bypass valve	Check for physical damage or signs of failure; replace if necessary.
Check wiring and connectors	Look for damaged, corroded, or loose connections that could disrupt the circuit.
Test the valve’s operation	Use a scanner to activate the solenoid and check for proper response.
Verify valve resistance	Ensure the resistance level matches OEM specifications to confirm functionality.
Examine the ECM	Check for any issues that could affect its ability to control the bypass valve circuit.

In the cases provided, fixes ranged from replacing a faulty valve to securing a loose wiring harness connector. These solutions underscore the importance of thorough diagnostics to identify and correct the root cause of the P0035 code, ensuring the turbocharger system functions optimally and maintains the engine’s performance.