If your OBD-II scanner displays P0045, your vehicle’s Engine Control Module (ECM) or Powertrain Control Module (PCM) has detected an open circuit or electrical malfunction in the turbocharger or supercharger boost control “A” circuit.

The generic SAE definition for P0045 is:

Turbocharger/Supercharger Boost Control “A” Circuit/Open

This code applies to forced-induction engines that use an electronically controlled:

Turbocharger wastegate actuator
Boost control solenoid
Variable-geometry turbo actuator
Supercharger bypass actuator
Boost pressure control valve
Electronic boost control motor

The ECM uses these components to regulate boost pressure under changing engine speed, load, throttle position, temperature, and atmospheric conditions.

When the ECM commands the boost control device but detects no current flow, an open circuit, or an electrical response outside the expected range, it stores P0045 and illuminates the Check Engine Light.

Common causes include:

Disconnected boost control solenoid
Open control wire
Broken power or ground circuit
Failed wastegate actuator
Failed boost control solenoid
Corroded connector
Melted or damaged wiring
Blown fuse
Failed relay
Faulty variable-geometry turbo actuator
ECM driver failure

P0045 can cause low boost, reduced power, limp mode, poor acceleration, or complete loss of turbocharger control.

For additional diagnostic information, visit:

Complete OBD-II Code Library: https://my.prostreetonline.com/dtc-obdii/
Body B-Code Library: https://my.prostreetonline.com/dtc-doctor/b-code-obd-ii-codes/
Chassis C-Code Library: https://my.prostreetonline.com/dtc-doctor/c-code-obd-ii-codes/

P0045 Quick Facts

Item	Information
OBD-II Code	P0045
Description	Turbocharger/Supercharger Boost Control “A” Circuit/Open
Category	Powertrain
System	Forced Induction / Boost Control
Circuit	Boost Control “A”
Severity	Moderate to High
Safe to Drive?	Sometimes
Typical Repair Cost	$100–1,500+

What Does P0045 Mean?

P0045 means the ECM has detected an open circuit or loss of electrical continuity in the primary turbocharger or supercharger boost control circuit.

The letter “A” does not necessarily identify a specific physical location. Instead, it refers to the primary boost control circuit defined by the vehicle manufacturer.

Depending on the engine, Boost Control “A” may control:

Turbocharger wastegate solenoid
Electronic wastegate actuator
Variable nozzle turbo actuator
Supercharger bypass valve
Turbo vane control motor
Vacuum control solenoid

An open circuit means electrical current cannot flow through the circuit as intended.

This may occur because of:

Broken wire
Disconnected connector
Open solenoid coil
Failed actuator motor
Blown fuse
Faulty ECM driver

How Turbocharger Boost Control Works

A turbocharger produces boost by using exhaust energy to spin a turbine connected to a compressor wheel.

Without control, boost pressure could rise beyond safe limits.

The ECM regulates boost using one or more devices, including:

Wastegate
Wastegate actuator
Boost control solenoid
Variable turbo vanes
Electronic actuator motor
Bypass valve

The ECM calculates target boost using data from:

Throttle position
Engine speed
Engine load
Intake air temperature
Manifold pressure
Barometric pressure
Knock sensors
Exhaust temperature
Transmission status

It then commands the boost control actuator to increase or reduce boost.

What Is the Boost Control “A” Circuit?

The Boost Control “A” circuit is typically the primary electrical circuit used to operate the turbocharger or supercharger boost control device.

The circuit may include:

Battery power
Ignition voltage
Fuse
Relay
ECM control wire
Ground circuit
Solenoid coil
Actuator motor
Position feedback circuit

On some vehicles, the ECM uses pulse-width modulation to regulate a boost control solenoid.

On others, the ECM controls a fully electronic wastegate actuator with:

Motor power
Motor ground
Position sensor
Reference voltage
Signal return

The exact design varies considerably by manufacturer.

What Does “Circuit/Open” Mean?

The word “open” means the electrical path is interrupted.

An open circuit may be caused by:

Disconnected connector
Broken wire
Corroded terminal
Burned-out solenoid coil
Failed actuator motor winding
Blown fuse
Failed relay
Damaged ECM circuit

When the circuit is open, the ECM may command the boost actuator but detect:

No current flow
No voltage change
No actuator movement
No position feedback
Incorrect boost response

How the ECM Detects P0045

The ECM may store P0045 when:

Boost control current is zero
Solenoid resistance is outside specification
The actuator does not respond
The circuit remains open
Feedback voltage is missing
Commanded boost and actual boost do not agree
The electronic wastegate position does not change

The code may set:

Immediately after startup
During a key-on self-test
Under acceleration
During a boost control test
When the ECM commands actuator movement

Some vehicles may require the fault to occur during multiple drive cycles before illuminating the Check Engine Light.

Symptoms of P0045

Common symptoms include:

Check Engine Light
Reduced engine power
Limp mode
Low boost
No boost
Poor acceleration
Sluggish throttle response
Increased fuel consumption
Black exhaust smoke on diesel engines
Whistling or unusual turbo noises
Overboost or underboost codes
Cruise control disabled
Traction or stability warnings

In some cases, the vehicle may feel normally aspirated because the turbocharger is producing little or no usable boost.

Common Causes of P0045

1. Disconnected Boost Control Solenoid

A disconnected electrical connector is one of the simplest and most common causes.

This often occurs after:

Turbo replacement
Intake repairs
Engine work
Exhaust repairs
Wastegate service

2. Failed Boost Control Solenoid

The internal coil may burn open and stop conducting current.

A failed solenoid may cause:

No boost control
Low boost
Overboost protection
Limp mode

3. Broken Control Wire

Harness damage may interrupt the ECM control circuit.

Common damage locations include:

Near the turbocharger
Around heat shields
Behind the engine
Near the exhaust manifold
At harness bends

4. Failed Electronic Wastegate Actuator

Many newer turbocharged engines use an electronic wastegate actuator instead of a vacuum-controlled system.

The actuator may fail because of:

Open motor winding
Internal gear damage
Position sensor failure
Heat damage
Water intrusion

Some manufacturers require replacing the complete turbocharger assembly if the actuator is not sold separately.

5. Corroded Connector

Heat, water, road salt, and oil contamination can damage boost control connectors.

Inspect for:

Green corrosion
White oxidation
Bent terminals
Loose pins
Water intrusion
Broken connector locks

6. Blown Fuse

Some electronic actuators receive power through a dedicated fuse.

A blown fuse may be caused by:

Shorted actuator
Harness damage
Internal motor failure
Incorrect previous repair

Do not replace a blown fuse repeatedly without diagnosing the cause.

7. Failed Relay

Certain systems use a relay to provide power to the boost control actuator.

A failed relay may create an open power circuit.

8. Heat-Damaged Wiring

Turbochargers operate at extremely high temperatures.

Wiring routed too close to the turbine housing or exhaust manifold may become:

Brittle
Melted
Burned
Open internally

9. Poor Ground

A loose or corroded ground can prevent the actuator or solenoid from operating.

Ground failures may occur at:

Engine block
Cylinder head
Chassis ground
Harness splice
ECM ground

10. Faulty ECM Driver

The ECM controls the boost solenoid or actuator through an internal transistor or driver circuit.

If the driver fails open, the ECM may be unable to complete the circuit.

ECM failure is rare and should only be considered after all wiring and components have been tested.

11. Incorrect Replacement Component

An incorrect solenoid or actuator may have:

Wrong resistance
Wrong connector pinout
Incorrect operating range
Incompatible calibration

Aftermarket parts may also trigger P0045 if they do not match factory electrical specifications.

P0045 vs Related Boost Control Codes

Code	Description
P0045	Turbocharger/Supercharger Boost Control “A” Circuit/Open
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
P0234	Turbocharger/Supercharger Overboost Condition
P0299	Turbocharger/Supercharger Underboost Condition

In general:

P0045 indicates an open electrical circuit.
P0046 indicates the circuit or actuator is not operating within its expected range.
P0047 indicates circuit voltage is too low.
P0048 indicates circuit voltage is too high.
P0234 indicates actual boost is too high.
P0299 indicates actual boost is too low.

Is P0045 Serious?

P0045 should be considered moderately to highly serious.

The engine may enter limp mode to protect:

Turbocharger
Engine
Catalytic converter
Diesel particulate filter
Transmission

If boost control is lost, the engine may experience:

Severe underboost
Unexpected overboost
Poor acceleration
Excessive exhaust smoke
High exhaust temperatures
Turbocharger damage

The exact risk depends on how the system fails.

Can You Drive With P0045?

The vehicle may still be driveable, but continued driving is not always recommended.

Short-distance driving may be possible if:

The engine runs smoothly
No abnormal turbo noises are present
The Check Engine Light is steady
The vehicle is only experiencing low boost

Stop driving and arrange repairs if:

The vehicle enters severe limp mode
The Check Engine Light flashes
The engine produces heavy smoke
Boost suddenly spikes
The turbocharger makes grinding or siren-like noises
Oil consumption increases
The engine stalls or surges

Loss of boost control can create unpredictable engine performance.

How to Diagnose P0045

Step 1: Scan for Additional Codes

Record all stored, pending, and permanent codes.

Related codes may include:

P0046 – Boost Control “A” Range/Performance
P0047 – Boost Control “A” Circuit Low
P0048 – Boost Control “A” Circuit High
P0234 – Overboost Condition
P0299 – Underboost Condition
P2563 – Turbocharger Boost Control Position Sensor Circuit Range/Performance
P2261 – Turbocharger Bypass Valve Mechanical
P2262 – Turbo Boost Pressure Not Detected

Freeze-frame data may show when the fault occurred.

Step 2: Identify the Boost Control System

Determine whether the vehicle uses:

Vacuum wastegate actuator
Electronic wastegate actuator
Variable-geometry turbo actuator
Boost control solenoid
Supercharger bypass actuator

Use factory service information and wiring diagrams.

Step 3: Inspect the Connector

Check the boost control connector for:

Loose connection
Broken lock
Corrosion
Bent terminals
Water intrusion
Oil contamination
Backed-out pins

Reconnect the connector securely.

Step 4: Inspect the Wiring Harness

Look for:

Broken wires
Melted insulation
Chafing
Pinched wiring
Contact with exhaust components
Improper repairs

Heat damage is particularly common near turbochargers.

Step 5: Check the Fuse and Relay

Verify the boost actuator or solenoid fuse has power on both sides.

If the fuse is blown:

Disconnect the actuator
Inspect for a short
Test harness resistance
Verify the replacement fuse does not immediately fail

Test the relay if the system uses one.

Step 6: Measure Solenoid or Actuator Resistance

Disconnect the boost control component and measure resistance.

Possible results include:

Infinite resistance: open coil or motor winding
Resistance above specification: internal damage
Resistance below specification: possible short

Compare readings with manufacturer specifications.

Step 7: Verify Power and Ground

With the ignition on or actuator commanded on, check for:

Battery voltage
Ground integrity
ECM control signal

Do not assume a component is defective until power and ground have been verified.

Step 8: Test Circuit Continuity

Check continuity between:

Actuator and ECM
Actuator and power source
Ground circuit and chassis
Position sensor and ECM

Repair any open or high-resistance circuits.

Step 9: Perform Voltage-Drop Testing

A wire may pass a simple continuity test but fail under load.

Perform voltage-drop tests across:

Power circuit
Ground circuit
Connector terminals
Relays
Wiring splices

Step 10: Command the Boost Actuator

Use a bidirectional scan tool to command the boost actuator or solenoid.

Observe:

Commanded duty cycle
Actuator position
Wastegate movement
Current draw
Position feedback
Boost pressure response

If the ECM commands movement but the actuator remains inactive, suspect an open circuit or failed actuator.

Step 11: Inspect Vacuum Lines

On vacuum-controlled systems, inspect:

Cracked hoses
Disconnected lines
Collapsed hoses
Incorrect routing
Vacuum pump output

A vacuum leak does not normally cause an electrical open code by itself, but it may create additional boost performance codes.

Step 12: Inspect Mechanical Wastegate Operation

Verify the wastegate arm or turbo vanes move freely.

A seized mechanism may overload the actuator and lead to electrical failure.

Step 13: Check Technical Service Bulletins

Look for bulletins involving:

Electronic wastegate actuators
Harness routing
Turbo heat damage
Updated connectors
ECM calibration
Actuator relearn procedures

Step 14: Perform Actuator Calibration

Some electronic wastegate actuators require:

Initialization
Relearn
Adaptation
Position calibration

Replacing the actuator without performing calibration may cause the code to return.

Step 15: Verify the Repair

After repairs:

Clear all codes.
Start the engine.
Monitor commanded and actual boost.
Command the actuator through its range.
Complete a road test.
Confirm P0045 does not return.
Verify no overboost or underboost codes are stored.

Common Repairs and Costs

Repair	Estimated Cost
Connector repair	$75–250
Wiring repair	$100–500
Fuse replacement	$10–50
Boost control solenoid replacement	$120–400
Vacuum line replacement	$50–200
Electronic wastegate actuator replacement	$300–1,200
Turbo actuator calibration	$100–300
Turbocharger replacement	$1,200–4,000+
ECM software update	$100–300
ECM replacement	$1,000–2,500+

Repair costs vary significantly depending on whether the actuator is available separately.

On some modern vehicles, a failed $200 actuator is permanently attached to a turbocharger that costs several thousand dollars—because apparently modular repair was considered too generous.

Common Diagnostic Mistakes

Avoid these common mistakes when diagnosing P0045:

Replacing the turbocharger before testing the circuit
Replacing the boost solenoid without checking power
Ignoring heat-damaged wiring
Assuming P0045 is caused by a boost leak
Failing to inspect the connector
Replacing a fuse without locating the fault
Confusing electrical and mechanical wastegate problems
Skipping actuator calibration
Replacing the ECM before circuit testing
Testing resistance without disconnecting the component

Vehicles Commonly Affected

P0045 may appear on turbocharged or supercharged vehicles from:

Audi
BMW
Chevrolet
Chrysler
Dodge
Ford
GMC
Honda
Hyundai
Infiniti
Jeep
Kia
Land Rover
Lexus
Mercedes-Benz
MINI
Mitsubishi
Nissan
Porsche
Ram
Subaru
Toyota
Volkswagen
Volvo

It is also common on turbo-diesel engines using electronic variable-geometry turbochargers.

How to Prevent P0045

Reduce the likelihood of P0045 by:

Securing boost control wiring away from exhaust heat
Reinstalling turbo heat shields
Inspecting connectors during turbo service
Repairing oil leaks that contaminate wiring
Using OEM-quality solenoids and actuators
Avoiding unsealed wiring repairs
Replacing brittle vacuum lines
Performing required actuator calibration
Checking the harness after engine or turbo replacement
Addressing boost control codes promptly

Frequently Asked Questions

What does P0045 mean?

P0045 means the ECM has detected an open circuit or loss of electrical continuity in the turbocharger or supercharger Boost Control “A” circuit.

What is Boost Control “A”?

Boost Control “A” is the primary boost control circuit identified by the manufacturer. It may operate a wastegate solenoid, electronic actuator, variable turbo vanes, or supercharger bypass actuator.

What causes P0045 most often?

Common causes include a disconnected boost control component, broken wiring, failed solenoid, open actuator motor, corroded connector, or blown fuse.

Can a bad turbocharger cause P0045?

The turbocharger itself does not usually cause an electrical circuit-open code.

However, an electronic actuator attached to the turbo may fail and trigger P0045.

Can a boost leak cause P0045?

A boost leak usually causes underboost codes such as P0299 rather than an electrical circuit-open code.

Can I drive with P0045?

Possibly, but the vehicle may have little or no boost and may enter limp mode. Continued driving is not recommended if the vehicle smokes, surges, overboosts, or makes abnormal turbo noises.

Will replacing the boost control solenoid fix P0045?

It may, but only if the solenoid coil is open.

The wiring, connector, fuse, power, ground, and ECM control circuit should be tested first.

Can a blown fuse cause P0045?

Yes.

A blown actuator or solenoid fuse may create an open circuit. The underlying reason for the fuse failure should still be diagnosed.

Does P0045 mean the wastegate is stuck?

Not necessarily.

P0045 is primarily an electrical circuit code. A stuck wastegate may cause range/performance, underboost, or overboost codes.

Is P0045 the same as P0046?

No.

P0045 indicates an open circuit, while P0046 indicates that the boost control circuit or actuator is operating outside its expected range.

Final Thoughts

The P0045 code indicates an open electrical circuit in the turbocharger or supercharger Boost Control “A” system. The ECM has attempted to control the boost solenoid or actuator but detected no current flow, no response, or missing feedback.

Start diagnosis by identifying the type of boost control system used by the vehicle. Inspect the connector and heat-exposed wiring, then verify the fuse, relay, power supply, ground, component resistance, and ECM control circuit.

Do not replace the turbocharger simply because the code contains the word “turbocharger.” In many cases, P0045 is caused by a broken wire, failed solenoid, disconnected connector, or defective electronic wastegate actuator.

Continue diagnosing turbocharger and boost-control faults with these Pro Street guides:

Boost Control Circuit Codes

P0046 Code Explained: Turbocharger/Supercharger Boost Control “A” Circuit Range/Performance
P0047 Code Explained: Turbocharger/Supercharger Boost Control “A” Circuit Low
P0048 Code Explained: Turbocharger/Supercharger Boost Control “A” Circuit High

Turbocharger Performance Codes

P0234 Code Explained: Turbocharger/Supercharger Overboost Condition
P0299 Code Explained: Turbocharger/Supercharger Underboost Condition
P2261 Code Explained: Turbocharger Bypass Valve Mechanical
P2262 Code Explained: Turbo Boost Pressure Not Detected
P2563 Code Explained: Turbocharger Boost Control Position Sensor Circuit Range/Performance

Related Bypass Valve Codes

P0033 Code Explained: Turbocharger Bypass Valve Control Circuit
P0034 Code Explained: Turbocharger Bypass Valve Control Circuit Low
P0035 Code Explained: Turbocharger Bypass Valve Control Circuit High
P0039 Code Explained: Turbocharger Bypass Valve Control Circuit Range/Performance

Browse the complete Pro Street diagnostic libraries:

Complete OBD-II Code Guide: https://my.prostreetonline.com/dtc-obdii/
B-Code OBD-II Library: https://my.prostreetonline.com/dtc-doctor/b-code-obd-ii-codes/
C-Code OBD-II Library: https://my.prostreetonline.com/dtc-doctor/c-code-obd-ii-codes/

P0045 Code Explained: Turbocharger/Supercharger Boost Control “A” Circuit/Open Causes, Symptoms & Fixes