What does the P0045 fault code mean?
The P0045 fault code, applicable to all car manufacturers, means “Turbocharger/Supercharger Boost Control A Circuit/Open“.
Background information: A turbocharger uses the inertial force of exhaust gases from the engine to drive a turbine, which in turn drives a coaxial impeller to pressurize the intake air, thereby increasing the car’s power. A supercharger is an air compressor used to increase the intake air of an internal combustion engine. More intake air provides the engine with more oxygen, allowing the control module to deliver more fuel, thus increasing output power. The turbocharger/supercharger boost controller’s function is to, when the boost pressure reaches a set value, use air pressure to push a wastegate actuator (pneumatic mechanical type) to redirect some exhaust gases around the turbine, thereby reducing the turbine speed and controlling the boost level. This fault code indicates that the voltage of the turbocharger/supercharger boost control A circuit is outside the calibrated normal range.
Symptoms of P0045 Error Code:
- Loss of engine power during acceleration;
- Turbocharger fails to start or is unstable;
- Error in ECU memory;
- Increased fuel consumption;
- Unstable engine operation;
- Check the engine indicator on the dashboard.
Important! If the circuit is unstable, error P0045 may temporarily disappear, but will reappear when the boost valve is reactivated.
Main Causes of P0045 Error Code:
- Ground fault in turbo control circuit;
- Damaged or broken wiring or connections;
- Faulty boost control solenoid valve;
- Faulty turbo actuator electric drive;
- Engine control unit (ECU) problem.
How to Diagnose P0045 Error Code?
Step 1: Use an OBD2 scanner to read the error code.
Step 2: Check the turbo valve wiring for damage or overheating.
Step 3: Check the connectors for corrosion, loose contacts, or dirt.
Step 4: Use a multimeter to measure the resistance of the valve control circuit.
Step 5: Test the solenoid valve (actuator) individually by direct power supply.
Possible Causes and Diagnostic Methods
| Possible Cause | How to Check? |
| Open Circuit in Wiring | With the battery disconnected, check for continuity in the wires between the PCM connector and the boost control solenoid connector. An open circuit will show infinite resistance (OL). |
| Faulty Boost Control Solenoid | Measure the solenoid’s coil resistance. Also, perform a functional test by applying 12V directly to the solenoid (briefly) and listening for an audible “click.” No click suggests a faulty solenoid. |
| Blown Fuse | Locate the fuse for the boost control circuit (check the owner’s manual or underhood fuse box diagram) and inspect it visually or test it with a multimeter. |
| Faulty Turbo Vane Position Sensor | With a scan tool, monitor the vane position sensor reading while manually moving the actuator arm (if accessible). The reading should change smoothly. Also, check its power (5V reference) and ground. |
| Vacuum Leak | Use a vacuum pump/gauge to test the integrity of vacuum lines and the wastegate actuator. It should hold vacuum without leaking down quickly. |
| Faulty PCM Driver Circuit | This is a last resort. Using an oscilloscope, check for a pulsed signal from the PCM at the solenoid connector when the engine is running. No signal may indicate a faulty PCM. |
Required tools: OBD2 scanner; digital multimeter; insulating tape, heat shrink tubing; automotive wiring diagram.
How to resolve P0045 error code? (Solution to the problem)
Simple handling method
- Clean and secure the solenoid valve connector;
- Replace the damaged fuse;
- Reset the error and drive again to check.
In-depth diagnosis and repair
- Replace the faulty turbo control solenoid valve;
- Repair damaged wiring;
- Adjust the turbocharger if necessary;
- If signals are missing or erroneous, check and replace the engine control unit.
Troubleshooting through symptoms
| Symptoms | Possible solutions |
| Turbocharger cannot start | Check solenoid valve and power supply |
| Increased fuel consumption | Diagnose turbo control circuit |
| Check engine stability | Count error, check circuit |
| Power failure | Check actuator, replace if necessary |
Common Error Code P0045 in Vehicles
Ford P0045 (EcoBoost engines – 1.0L, 1.5L, 1.6L, 2.0L, 2.3L, 2.7L, 3.5L): Very common in Ford Focus ST, Fiesta ST, Escape, Fusion, Mustang EcoBoost, and F-150 EcoBoost. The wastegate solenoid is often located on the turbocharger or nearby. Wiring harnesses near the hot turbo can become brittle and crack. A professional obd2 code reader with Ford-specific PIDs is useful for testing “Desired Boost Pressure” vs. “Actual Boost Pressure.”
Volkswagen/Audi P0045 (TSI and TDI engines – 1.4L, 1.8L, 2.0L, 3.0L): Frequent in VW Golf GTI, Jetta, Passat, Audi A3, A4, Q5. These vehicles often use a vacuum-controlled wastegate actuator or an electronic VNT actuator. Check the vacuum solenoid (N75 valve) and all associated vacuum lines. VAG-com (VCDS) or OBDeleven tools are highly recommended for in-depth diagnosis and actuator basic settings.
General Motors (GM) P0045 (Duramax Diesel, 2.0L Turbo, 1.4L Turbo): Appears in Chevrolet Cruze Diesel, Silverado/Sierra with Duramax, Equinox, Malibu. On Duramax engines, the code often relates to the Variable Geometry Turbo (VGT) actuator or its position sensor. The actuator is prone to carbon buildup. Using a professional vehicle diagnostics tool to command vane position is crucial.
BMW P0045 (N54, N55, N63, B58 engines): Occurs in BMW 335i, 535i, X3, X5, and other turbocharged models. Diagnosis typically requires ISTA (BMW’s diagnostic software) to run guided tests on the boost pressure control valve (often called the “Diverter Valve” or “Wastegate Solenoid”). Check for vacuum leaks at the valve and the diaphragm-operated wastegate actuators.
Mercedes-Benz P0045 (OM642, OM651, M276 turbo engines): Seen in Mercedes C300, E350, GLK, Sprinter. Requires STAR Diagnostic system for accurate fault reading and to actuate the boost pressure control solenoid. The solenoid is often part of a complicated vacuum system. Inspect the intricate network of vacuum lines and check valves.
Subaru P0045 (FA20DIT, FA24DIT engines): Affects Subaru WRX, STI, Ascent, Legacy XT, Outback XT. The turbocharger boost control solenoid is mounted in the engine bay. A common issue is a cracked or disconnected vacuum hose running from the solenoid to the wastegate actuator on the turbo. Also check the solenoid’s electrical connector for corrosion.
Hyundai/Kia P0045 (Theta II 2.0T, Gamma 1.6T, Smartstream engines): Common in Hyundai Sonata 2.0T, Tucson 1.6T, Kia Optima Turbo, Sportage Turbo. The boost control solenoid valve is often located on the firewall or near the intake manifold. Check for Technical Service Bulletins (TSBs) related to updated solenoid part numbers.
Nissan/Infiniti P0045 (MR16DDT, VR30DDTT engines): Found in Nissan Juke, Qashqai, Infiniti Q50 Red Sport. The service manual outlines a specific diagnostic procedure checking power supply and output signal circuits to the turbo boost control solenoid valve. The connector can suffer from heat degradation.
Honda/Acura P0045 (K20C1, J30A turbo engines): In Honda Civic Type R, Accord 2.0T, Acura RDX, TLX. Honda’s system is precise. A faulty wastegate actuator or a sticking wastegate flapper itself can trigger this code. Inspect the mechanical linkage on the turbo for free movement.
Land Rover/Jaguar P0045 (Ingenium diesel and petrol engines): Affects Range Rover Evoque, Discovery Sport, Jaguar XE. These vehicles are prone to issues with the turbocharger actuator motor. A specialized scan tool like JLR’s SDD or a top-tier aftermarket tool is often needed to perform actuator learn/calibration procedures after replacement.
Mazda P0045 (SkyActiv-G 2.5T engine): In Mazda CX-5 Turbo, CX-9, Mazda6 Turbo, Mazda3 Turbo. Diagnose by checking the boost control solenoid valve operation and the vacuum lines to the wastegate. Also, inspect the charge air cooler piping for leaks that could affect boost pressure readings.
Volvo P0045 (Drive-E T5, T6 engines): Seen in Volvo S60, XC60, XC90. Volvo’s system integrates the boost control with the engine management tightly. Diagnosis is best performed with Volvo’s VIDA system to monitor target vs. actual boost and to test the turbo control valve.
Isuzu/Hino P0045 (4HK1, J08E diesel engines in trucks): Common in Isuzu NPR, Hino 338, and other medium-duty trucks. The code often relates to the VGS (Variable Geometry System) control unit or actuator. These systems are robust but can suffer from carbon buildup on the turbo vanes. Specialized heavy-duty diagnostic software is helpful.
Mitsubishi Fuso P0045 (4M4 series diesel engines): In Mitsubishi Fuso trucks. The diagnostic procedure involves checking the VGT actuator motor circuit resistance and for shorts to power or ground. The wiring harness in commercial vehicles can suffer from vibration damage.
P0045 Frequently Asked Questions
What is the first thing I should do when I see code P0045?
The first step is to use a reliable obd2 scanner to confirm the code and check for any other related codes (like P0234 – Overboost, or P2263 – Turbo Boost Pressure Not Detected). Then, perform a detailed visual inspection of all wiring, connectors, and vacuum lines associated with the turbocharger boost control system. Look for obvious damage, disconnections, or leaks.
Is it safe to drive my car with the P0045 code?
You can drive for a short distance cautiously, but it is not recommended for extended periods. The engine will likely be in a reduced-power “limp mode” to protect itself. More importantly, if the cause is a stuck wastegate (causing overboost), you risk severe engine damage from detonation. If the cause is an open circuit (causing underboost), you’ll have poor performance but less immediate risk. Have it diagnosed promptly.
How much does it typically cost to repair a P0045 error?
Costs vary widely. A simple wiring repair or solenoid replacement might cost between $200 and $500 for parts and labor. Replacing a turbocharger vane position sensor or MAP sensor could be $300-$700. A full turbocharger replacement is the most expensive, ranging from $1,500 to over $4,000 depending on the vehicle. Using a capable vehicle code reader for accurate diagnosis can save money by pinpointing the exact fault.
Can I fix a P0045 code myself?
Yes, if you have intermediate mechanical and electrical skills. You will need basic hand tools, a digital multimeter, and an OBD2 scanner. Replacing a solenoid or sensor is often straightforward. However, diagnosing a wiring fault deep in the harness or replacing a turbocharger is complex and may require specialized tools and knowledge. Always disconnect the battery and allow the turbo/exhaust to cool completely before working.
What’s the difference between P0045, P0046, P0047, and P0048?
All relate to the “Boost Control A Circuit.” P0045 indicates an “Open” circuit. P0046 indicates a “Range/Performance” problem (the circuit works but values are out of expected range). P0047 indicates a “Low” circuit condition (short to ground or low voltage). P0048 indicates a “High” circuit condition (short to power or high voltage). P0045 is specifically an open or break in the circuit.
Will disconnecting the battery clear the P0045 code?
It may temporarily turn off the Check Engine Light, but the code will remain stored as a “permanent” or “pending” code in the PCM’s memory. To properly clear the code and extinguish the light, you must use an OBD2 diagnostic scanner after the underlying issue is fixed.
Can a bad turbocharger cause code P0045?
Yes, but indirectly. A mechanically seized variable geometry turbo (VGT) can prevent the actuator from moving, which the PCM may interpret as an open circuit in the control system. Similarly, a completely failed wastegate actuator can cause an open circuit fault. The code points to the control circuit, but the root cause can be the mechanical component it’s trying to control.
My car failed emissions inspection with P0045. Will fixing it guarantee a pass?
Yes, once the P0045 code is repaired and cleared, and the vehicle completes a proper drive cycle to set all OBD-II monitors (especially the comprehensive component monitor), it should pass the OBD-II portion of the emissions test, provided no other faults are present.
After replacing the boost control solenoid, do I need to reset the ECU or perform a relearn?
In most cases, simply clearing the code with a car scanner is sufficient. The PCM will relearn the new solenoid’s parameters during driving. However, on some vehicles (particularly European brands like VW, BMW, Mercedes), a specific actuator adaptation or “basic setting” procedure may be required using a professional scan tool. Consult your vehicle’s service information.
What does “Circuit Open” specifically mean in P0045?
It means the Powertrain Control Module (PCM) has detected a break in the electrical circuit that controls the boost control solenoid. This break prevents electrical current from flowing, so the PCM cannot command the solenoid to operate. The break could be in the wiring, at a connector, or inside the solenoid coil itself.
Could a problem with the vehicle’s battery or alternator cause P0045?
Yes, a weak battery or failing alternator causing low system voltage could potentially lead to circuit malfunctions that the PCM interprets as an open circuit. Always check battery voltage (should be ~12.6V engine off, ~13.5-14.5V engine running) as part of your initial diagnosis.
How can I prevent P0045 from happening again?
Use high-quality OEM or equivalent replacement parts. Ensure all wiring repairs are properly insulated and the harness is secured away from heat sources and moving parts. On turbocharged vehicles, regular oil changes with the correct specification oil are critical to prevent carbon buildup on turbo vanes. Address any minor boost or vacuum leaks promptly.
Is P0045 the same on diesel and gasoline engines?
The code definition is identical – a boost control circuit open. However, the implementation differs. Diesel engines more commonly use Variable Geometry Turbos (VGTs) with electronic actuators, while gasoline turbos often use a wastegate controlled by a vacuum solenoid. The diagnostic approach is similar (check circuit integrity, then component), but the specific components and tests vary.
Can I use a universal boost control solenoid to fix this?
It is not recommended. Universal solenoids may have different flow characteristics, resistance values, or connector types. Using an incorrect solenoid can lead to poor boost control, performance issues, and the code returning. Always use the part specified for your vehicle’s make, model, and engine.
P0045 Related OBD2 Errors
- P0046 – Turbocharger/Supercharger Boost Control A Circuit Range/Performance
- P0047 – Turbocharger/Supercharger Boost Control A Circuit Low
- P0048 – Turbocharger/Supercharger Boost Control A Circuit High
- P0049 – Turbocharger/Supercharger Turbine Overspeed
- P004A – Turbocharger/Supercharger Boost Control A Circuit Intermittent/Erratic
- P0234 – Turbocharger/Supercharger Overboost Condition
- P0235 – Turbocharger Boost Sensor A Circuit Malfunction
- P0243 – Turbocharger Wastegate Solenoid A Malfunction
- P2563 – Turbocharger Boost Control Position Sensor Circuit
- P2564 – Turbocharger Boost Control Position Sensor Circuit Range/Performance
- P2565 – Turbocharger Boost Control Position Sensor Circuit Low
- P2566 – Turbocharger Boost Control Position Sensor Circuit High
Important Note! Code P0045 is a serious fault that disables the vehicle’s boost control system, leading to reduced performance and potential engine damage if overboost occurs. Diagnosis should always start with a thorough visual inspection of wiring and vacuum lines. Using a professional-grade vehicle diagnostics tool with bidirectional controls and live data graphing is highly recommended for accurate diagnosis. When working near the turbocharger or exhaust manifold, always allow components to cool completely to avoid severe burns. If you are not confident in diagnosing electrical or turbocharger systems, consulting a qualified technician is strongly advised.