P0045 is a turbocharger/supercharger boost control code that can show up on many modern turbocharged vehicles. When it appears, your engine computer is telling you that something is wrong with the boost control circuit, usually an “open” electrical issue. You might notice low power, a check engine light, or even limp mode. The good news is that this code is very fixable with a systematic approach. In this guide, you’ll learn what P0045 means, common causes, symptoms, and realistic repair options so you can plan your next steps.
What Does P0045 Mean?
P0045 is defined as “Turbocharger/Supercharger Boost Control ‘A’ Circuit Open.” In simple terms, your ECU commanded the turbo or supercharger control system to move, but it saw no proper electrical response from the “A” circuit. That “A” circuit usually controls a boost control solenoid, wastegate control valve, or variable geometry turbo actuator.
“Circuit open” means the ECU sees a break in the electrical path: a disconnected plug, broken wire, failed solenoid coil, or sometimes a bad internal driver in the ECU. The result is the ECU can’t properly control boost, so it sets P0045 and often reduces power to protect the engine.
Quick Reference
- Code: P0045
- Definition: Turbocharger/Supercharger Boost Control “A” Circuit Open
- Severity: Moderate to high (possible limp mode, low power)
- Typical Causes: Bad boost control solenoid, wiring fault, connector damage, turbo actuator issue
- Primary Symptoms: Low power, check engine light, poor acceleration
Real-World Example / Field Notes
In the shop, I see P0045 most often on turbo diesels and small turbo gas engines. A common scenario: the customer complains of “no power” and the truck feels like a naturally aspirated engine. Scan tool shows P0045 and maybe a few boost-related codes. On inspection, I often find a broken or oil-soaked connector at the boost control solenoid mounted near the turbo, or a rubbed-through harness on a bracket. Fix the wiring, clear the code, and the truck wakes right back up. Occasionally, the solenoid coil itself is open and needs replacement.
Symptoms of P0045
- Check engine light: The MIL/SES light will almost always be on when P0045 is stored.
- Low power / poor acceleration: The engine may feel sluggish, especially under load or when trying to pass.
- Limp mode: Some vehicles limit boost and fuel, making it hard to go above certain speeds.
- Low or no boost: Turbo may not spool properly; boost gauge (if equipped) shows less than normal.
- Increased fuel consumption: Engine may run less efficiently due to incorrect boost levels.
- Black smoke (diesels): On some diesel engines, incorrect boost can cause excess soot out the tailpipe.
- Whistling or unusual turbo noise: Not caused by the code itself, but may appear along with turbo issues that trigger P0045.
Common Causes of P0045
Most Common Causes
- Failed boost control solenoid: The internal coil opens up electrically, so the ECU can’t see or control it.
- Damaged wiring harness: Chafed, broken, or corroded wires between the ECU and the boost control solenoid or actuator.
- Loose or corroded connector: Poor contact at the solenoid or actuator plug causes an intermittent or open circuit.
- Faulty turbo actuator (VGT or electronic wastegate): Some actuators have built-in electronics that fail and appear as an open circuit.
- Aftermarket modifications: Poorly installed boost controllers, tuners, or deleted systems can disturb the factory circuit.
Less Common Causes
- ECU internal failure: A failed driver circuit inside the engine control unit can no longer power the solenoid.
- Blown fuse or relay: Some systems power the boost control valve through a dedicated fuse or shared circuit.
- Severe corrosion from road salt or water intrusion: Especially on vehicles driven in harsh climates or off-road conditions.
- Previous repair damage: Harness pulled too tight, pins bent, or wires pinched during turbo or engine work.
- Rodent damage: Mice chewing on wiring near the turbo area or firewall.
Diagnosis: Step-by-Step Guide
To diagnose P0045 correctly, you’ll want at least a good scan tool (capable of live data), a quality digital multimeter, and ideally a wiring diagram for your specific vehicle. A handheld vacuum pump can help on vacuum-operated systems. Basic hand tools and good lighting are also important because much of this work is done near the hot turbocharger area.
- Confirm the code and note freeze-frame data. Connect your scan tool, read P0045, and record engine RPM, load, speed, and temperature at the time the code set. This helps you know under what conditions the fault occurs.
- Check for related codes. Look for other turbo/boost codes like P0046, P0047, P0234, or sensor codes. Multiple codes can point you toward a shared wiring issue or a failing turbo actuator.
- Perform a visual inspection. With the engine off and cool, inspect the boost control solenoid/actuator, wiring, and connectors. Look for broken clips, oil-soaked connectors, melted insulation, or wires rubbing on brackets or the turbo heat shield.
- Verify power and ground at the solenoid. Using a wiring diagram, back-probe the connector with a multimeter. With the key on, you should see proper voltage on the power feed and a good ground path. If power or ground is missing, trace that circuit back toward the fuse box or ECU.
- Check solenoid or actuator coil resistance. With the connector unplugged and key off, measure resistance across the solenoid or actuator pins. An “open” reading (infinite resistance) usually means a failed component. Compare your reading to service manual specs.
- Wiggle test the harness. While monitoring resistance or live data on the scan tool, gently move the harness and connector. If readings jump or the code becomes intermittent, you’ve likely found a wiring or connector issue.
- Command the solenoid with a scan tool. Many scan tools allow you to command the boost control solenoid on and off. Listen/feel for a click or movement. If the ECU commands it but nothing happens, suspect the solenoid, actuator, or wiring.
- Inspect fuses and shared circuits. Check for any blown fuses related to engine controls, turbo control, or emissions. If a fuse is blown, find out why before just replacing it.
- Check turbo mechanical function. On variable geometry turbos or electronic wastegates, verify that the linkage or vanes move freely by hand (engine off, cooled down). A stuck mechanism can overload the actuator and sometimes lead to electrical failure.
- Evaluate ECU if all else tests good. If power, ground, wiring, and the solenoid/actuator all test within spec, you may be dealing with a rare ECU driver fault. At this point, professional-level diagnosis or an OEM-level scan tool is highly recommended.
Pro tip: Use Mode $06 data (if your scan tool supports it) to look at turbo/boost control test results. This can show borderline failures before they set additional hard codes, helping you catch an intermittent wiring issue early.
Possible Fixes & Repair Costs
Repairs for P0045 range from simple connector repairs to replacing the turbocharger actuator or even the ECU. Costs vary based on your vehicle, parts pricing, and labor rates in your area.
- Repair or replace connectors/wiring: Splicing in new wire or replacing a damaged plug typically costs $50–$250, depending on labor time and access.
- Replace boost control solenoid: Common repair; parts are often $50–$200, with total job cost around $150–$400.
- Replace electronic turbo actuator: On some diesels and modern gas engines, actuators can run $300–$800 for parts, with total repair often $500–$1,200.
- Turbocharger replacement (if damaged or seized): Much less common as a direct cause of P0045, but if needed, expect $1,000–$3,000+ depending on vehicle and whether you use new or remanufactured parts.
- ECU repair or replacement: Rare but expensive; typically $600–$1,500 including programming.
Typical repair cost ranges for P0045 are roughly $150–$600 for wiring or solenoid issues and $500–$1,500+ if the actuator or turbo assembly is involved. Costs are heavily influenced by vehicle make, parts availability, labor rates, and how difficult it is to access the turbo area.
Can I Still Drive With P0045?
In many cases, you can still drive with P0045, but the vehicle will likely have reduced power and may enter limp mode. Short trips to get home or to a repair shop are usually fine if the engine runs smoothly and there are no severe noises or smoke. However, driving for an extended period with improper boost control can stress the engine, increase fuel consumption, and potentially cause further issues. If you notice heavy smoke, loud turbo noises, or severe lack of power, it’s best to limit driving and have the vehicle inspected as soon as possible.
What Happens If You Ignore P0045?
Ignoring P0045 can lead to long-term problems such as excessive soot buildup (especially on diesels), clogged DPFs, higher exhaust temperatures, and accelerated wear on the turbocharger. You may also fail emissions tests and live with permanently reduced performance and fuel economy. Addressing the code early usually keeps the repair simpler and cheaper.
Related Codes
- P0027 – Exhaust Valve Control Solenoid Circuit Range/Performance Bank 1
- P0026 – Intake Valve Control Solenoid Circuit Range/Performance Bank 1
- P0019 – Crankshaft Position Camshaft Position Correlation Bank 2 Sensor B
- P0018 – Crankshaft Position Camshaft Position Correlation Bank 2 Sensor A
- P0017 – Crankshaft Position Camshaft Position Correlation Bank 1 Sensor B
- P0016 – Crankshaft Position Camshaft Position Correlation Bank 1 Sensor A
- P0009 – Engine Position System Performance Bank 2
- P0008 – Engine Position System Performance Bank 1
- P0007 – Fuel Shutoff Valve “A” Control Circuit High
- P0006 – Fuel Shutoff Valve “A” Control Circuit Low
Key Takeaways
- P0045 means the ECU detects an open circuit in the turbo/supercharger boost control “A” system.
- Most common causes are a failed boost control solenoid, wiring damage, or a bad turbo actuator.
- Symptoms include low power, check engine light, limp mode, and poor acceleration.
- Diagnosis focuses on checking wiring, connectors, solenoid resistance, and power/ground at the component.
- Repairs typically range from a simple wiring fix to actuator or turbo replacement, with costs varying widely by vehicle.
Vehicles Commonly Affected by P0045
P0045 shows up frequently on modern turbocharged vehicles, both gas and diesel. You’ll often see it on:
- Ford: Power Stroke diesels (6.0L, 6.4L, 6.7L) and EcoBoost gas engines.
- Chevrolet/GMC: Duramax diesel trucks and some turbocharged gas models.
- Dodge/Ram: Cummins turbo diesels and various turbocharged gas engines.
- Volkswagen/Audi: TDI diesels and TSI/TFSI turbo gas engines.
- Hyundai/Kia: 1.6T, 2.0T, and other GDI turbo engines.
- Subaru: WRX, STI, and other turbo boxer engines.
Any vehicle with an electronically controlled turbocharger or supercharger can potentially set P0045 if there’s a problem in the boost control circuit.
FAQ
Can P0045 go away on its own?
Sometimes P0045 may clear temporarily if the issue is intermittent, such as a loose connector making occasional contact. However, once the underlying wiring, solenoid, or actuator problem returns, the code will come back. It’s better to diagnose and fix the root cause than to rely on it disappearing on its own.
Is P0045 serious enough to tow the vehicle?
If the vehicle still runs smoothly, just with low power and no severe noises or smoke, you usually don’t need a tow. You can carefully drive to a shop. If you hear loud turbo whine, grinding, see heavy smoke, or the engine struggles badly, it’s safer to have it towed to avoid further damage.
How do I know if the boost control solenoid is bad or it’s just wiring?
You’ll need to test both. Measure resistance across the solenoid pins; an open or wildly out-of-spec reading points to a bad solenoid. Then verify power and ground at the connector. If the solenoid tests good but you’re missing power or ground, or moving the harness changes readings, the problem is likely in the wiring or connector.
Can a bad turbocharger itself cause P0045?
A purely mechanical turbo failure (worn bearings, damaged compressor wheel) usually doesn’t cause P0045 by itself. However, if the turbo’s electronic actuator or position sensor fails open, or if mechanical binding overloads the actuator, you can see P0045. In that case, you may need both actuator and turbo inspection.
How long can I safely drive with a P0045 code?
There’s no exact mileage, but it’s best to treat P0045 as a “fix soon” issue, not an emergency if the car still drives normally aside from reduced power. Driving for days or weeks with incorrect boost control can increase wear and lead to more expensive repairs. Schedule diagnosis and repair as soon as practical.