P0045 Turbo/Supercharger Boost Control A Circuit Open

Code P0045: Open Turbocharger/Supercharger Boost Control Circuit (Circuit A)

🔴 Severity and Risks

This error code indicates a serious problem requiring immediate attention. An open circuit in the turbo control system can lead to:

• Significant power loss and poor acceleration.
• Risk of engine knocking (detonation) due to an unbalanced air-fuel mixture.
• Overboost or underboost that can damage pistons, seals, or the turbocharger itself.
• Illumination of the Malfunction Indicator Lamp (MIL) and activation of a limp mode.

🚨 Common Symptoms

• Obvious lack of power (the turbo is not working).
• Abnormal whistling sounds from the engine (indicating an air leak or damaged turbo).
• Appearance of a warning message on the dashboard (e.g., “Reduce Engine Power”).
• Black or white smoke from the exhaust (incorrect combustion mixture).

🔧 Main Causes of Code P0045

1. Open electrical circuit: Cut wires, corroded connectors, or blown fuse.
2. Control solenoid failure: Wastegate solenoid or bypass valve stuck or short-circuited.
3. Turbo mechanical problem: Seized variable geometry turbine (VGT) vanes, oil leak, or damaged turbine.
4. Faulty sensor: MAP (Manifold Absolute Pressure) sensor or vane position sensor faulty.
5. PCM failure: Rare, but a software error or faulty internal circuit can be the cause.

📋 Step-by-Step Diagnostic Procedure

Step 1: Visual Inspection

• Visually inspect the wiring and connectors around the turbo for any damage, corrosion, or looseness.
• Inspect the intake system for potential air leaks (cracked hoses, worn seals).

Step 2: OBD2 Data Reading

• Use a bidirectional OBD2 scanner (like Autel MaxiCOM or Snap-On Solus) to:
  • Manually activate the control solenoid and observe its response.
  • Analyze live data: Boost Pressure PID value and VGT vane position.

Step 3: Control Solenoid Test

• Measure the resistance across the solenoid terminals and compare it to the manufacturer’s specifications (typically between 10 and 30 Ω).
• Perform a functional test by briefly applying 12V to check for the characteristic “click” sound.

Step 4: Sensor Verification

• Test the MAP sensor: Check for 5V (power supply), ground, and a variable signal that changes with pressure.
• Test the VGT position sensor: Its resistance should vary depending on the vane position.

Step 5: Turbo Mechanical Inspection

• Manually check the movement of the variable geometry vanes for possible seizure due to carbon buildup.
• Check the axial and radial play of the turbine. Excessive play indicates wear requiring turbo replacement.

💶 Solutions and Estimated Repair Costs

Problem	Solution	Average Cost
Faulty Solenoid	Replacement	€50 – €200
Damaged Wiring	Repair or Replacement	€80 – €300
Seized/Damaged Turbo	Cleaning or Replacement	€400 – €2500
Faulty MAP Sensor	Replacement	€80 – €250
PCM Reprogramming	Software Update	€100 – €300

❌ Common Mistakes to Avoid

• Ignoring air leaks: Even a small leak can completely skew the boost pressure.
• Forcing the engine: Avoid high RPMs until the problem is resolved to prevent further damage.
• Using non-approved parts: Lower quality solenoids may not meet specifications and cause recurring problems.

📖 Practical Case

Vehicle: Volkswagen Golf GTI 2.0 TSI
Problem: Code P0045 and severe power loss.
Diagnosis: Wastegate solenoid stuck in open position (infinite resistance measured).
Solution: Solenoid replacement (€120 part) and cleaning of electrical connectors. Problem completely resolved.

🚗 Frequently Affected Vehicles

• Ford: Focus ST, Fiesta ST (EcoBoost engines).
• Volkswagen / Audi: Golf GTI, A3, Q5 (TFSI and TDI engines).
• Chevrolet: Cruze Diesel, Silverado (Duramax engines).

🛠️ Professional Tips

1. Invest in a quality bidirectional OBD2 scanner to actively test actuators.
2. For seized variable geometry turbos, use a specific decarbonizing cleaner (like Wynns Turbo Cleaner) before considering a costly replacement.
3. Always check your vehicle’s Technical Service Bulletins (TSB). Some models (e.g., Ford TSB 18-101) have PCM software updates to resolve these issues.

⚠️ Warning: An untreated P0045 code can lead to serious engine damage. If the diagnosis is beyond your skills, consult a specialized mechanic without delay.