P0239
Fix within a few daysYour engine's computer detects a low voltage signal from the 'B' boost pressure sensor circuit, which monitors the pressure created by your turbocharger or supercharger.
Code P0239 means your engine's boost sensor 'B' circuit has a low voltage signal. Common causes: Faulty boost sensor (60%), wiring issues (30%). Drivability: Yes, for short trips only. Repair cost: $50-$200 DIY, $150-$500 professional.
Can I Drive With P0239?
Yes, for short trips only
Essential trips under 10 miles, avoid highways and heavy acceleration. Expect reduced power.
Stop driving immediately if: Flashing CEL, loud engine noises, burning smell, significant power loss, or engine overheating.
Symptoms of P0239
- 1Check Engine Light is on
- 2Reduced engine power or 'limp mode'
- 3Poor acceleration
- 4Engine hesitation or stumbling
- 5Rough idle
Common Causes of P0239
Parts most likely causing this code, ranked by probability
The sensor itself is faulty and sending an incorrect low voltage signal to the engine computer.
60% of P0239 cases are fixed by replacing this part
Damaged, corroded, or shorted wiring or a loose connector to the boost pressure sensor 'B' can cause a low voltage reading.
30% of P0239 cases are fixed by repairing wiring or connectors
A rare internal fault within the engine computer can incorrectly interpret the sensor's signal or fail to provide proper reference voltage.
5% of P0239 cases are fixed by replacing the PCM
A significant vacuum leak can cause the MAP sensor (often used as a boost sensor) to read abnormally low pressure, triggering the circuit low code.
5% of P0239 cases are fixed by repairing a vacuum leak
Check These First (Before Buying Parts)
- Visually inspect the boost pressure sensor 'B' and its electrical connector for any obvious damage, corrosion, or loose connections.
- Check for any obvious vacuum leaks around the intake manifold or turbocharger plumbing, as these can affect pressure readings.
How to Diagnose P0239
- 1Visually inspect the boost pressure sensor 'B' and its electrical connector for damage, corrosion, or loose connections.
- 2Check the wiring harness leading to the sensor for any signs of fraying, cuts, or shorts to ground.
- 3Using a multimeter, test the voltage at the boost pressure sensor 'B' connector to ensure it's receiving proper reference voltage (usually 5V) and ground.
- 4Backprobe the sensor's signal wire with a multimeter while the engine is running to check for a consistent voltage signal within specifications.
- 5If possible, use a scan tool to monitor the boost pressure sensor 'B' readings in real-time to see if they are erratic or consistently low.
P0239 on Popular Vehicles
Ford F-150
2011-2024EcoBoost engines are prone to MAP sensor failures or wiring issues leading to P0239. Inspect the sensor located on the intake manifold and its harness carefully.
75% fixed by replacing sensor or repairing wiring
Chevrolet Silverado
2014-2024On turbocharged Silverado models, P0239 can point to a failing boost pressure sensor or a compromised wiring harness, especially near the turbocharger where heat can degrade insulation.
70% fixed by replacing sensor or repairing wiring
Subaru WRX/STI
2002-2024Boost sensor issues are common on these performance vehicles. P0239 often indicates a faulty MAP sensor or a damaged harness due to engine bay heat or aftermarket modifications.
70% fixed by replacing sensor or repairing wiring
Frequently Asked Questions
What does P0239 mean?
P0239 indicates that your vehicle's engine computer has detected a low voltage condition in the circuit for the 'B' boost pressure sensor, which monitors the pressure generated by your turbocharger or supercharger.
Can I drive with P0239?
Yes, for short trips only. You will experience reduced engine power and possibly limp mode. Prolonged driving with this code can lead to further engine issues or damage to the turbo/supercharger system if the engine runs lean.
Will P0239 clear itself?
No, P0239 will not clear itself. The underlying electrical or sensor fault must be diagnosed and repaired. The Check Engine Light will remain on until the issue is resolved and the code is cleared, either by the vehicle's computer after several drive cycles or with a scan tool.
How do I fix P0239 myself?
Start by visually inspecting the boost pressure sensor 'B' and its wiring for damage. If the wiring looks good, test the sensor's voltage and resistance with a multimeter. If the sensor tests faulty, replacing it is a common DIY fix. Ensure all connections are clean and tight.
How much does it cost to fix P0239?
DIY repair costs for P0239 are typically $50-$200 for a new boost pressure sensor. Professional repair at a shop will cost $150-$500, including parts and labor.
P0239 keeps coming back - why?
If P0239 keeps returning, it indicates the initial repair did not address the root cause. This often means there's a persistent wiring issue (a short or open circuit), a faulty connector, or the PCM itself is failing. Double-check all electrical connections and consider a more thorough wiring harness inspection.
Will P0239 fail emissions/smog test?
Yes, P0239 will cause your vehicle to fail an emissions or smog test. The Check Engine Light being on automatically results in a failure in most states, and a fault in the boost pressure system can directly impact emissions.
What's the difference between P0239 and P0236?
P0239 refers specifically to a 'circuit low' condition for boost pressure sensor 'B', indicating an electrical fault with that sensor or its wiring. P0236 refers to a 'range/performance' issue for boost pressure sensor 'A', meaning the sensor's readings are inconsistent or outside expected parameters, which could be an electrical fault or an actual mechanical boost issue.
P0239 on Ford F-150?
On Ford F-150 EcoBoost engines, P0239 can often be traced to a faulty MAP sensor (which acts as the boost sensor) or issues with its electrical connector. Carbon buildup on the intake manifold can also sometimes indirectly affect MAP sensor readings, but the primary focus for P0239 is the sensor or wiring.
Questions to Ask Your Mechanic
Did you check the 5-volt reference voltage and ground at the boost pressure sensor 'B' connector?
Good answer: Yes, I confirmed the sensor is receiving proper 5V reference and a solid ground. The issue is with the signal wire or the sensor itself.
What were the live data readings from the boost pressure sensor 'B' when the engine was running?
Good answer: The live data showed the sensor reading consistently below expected atmospheric pressure or stuck at a very low voltage, confirming a circuit low condition.
Repair Cost Estimate
DIY Repair
Parts only
$50-$200
Shop Repair
Parts + labor
$150-$500
Save $100-$300 by doing it yourself
Difficulty
intermediate
Time
1-2 hours
Intermediate - Requires a multimeter for electrical testing and potentially a scan tool to monitor live data, but the physical replacement of the sensor is often straightforward.
Cost of Waiting
Ignoring P0239 can lead to your engine running lean due to incorrect boost readings, which can cause severe engine damage, including burnt valves, damaged pistons, or premature failure of your turbocharger/supercharger. A $100 sensor replacement now prevents a $2,000-$5,000 engine repair later.
While You're In There...
If you are accessing the intake system to replace the boost sensor, it's a good time to replace a dirty air filter, which affects engine performance and air flow.
If the boost sensor requires removal of the intake manifold for access, replacing the gaskets prevents future vacuum leaks and ensures a proper seal.
Tools You'll Need
- OBD-II Scan Tool
- Multimeter
- Basic Socket Set
- Screwdrivers
- Wire Strippers/Crimpers (if repairing wiring)
P0239 is a common sensor-related code on turbocharged or supercharged vehicles. Most repairs involve replacing a relatively inexpensive sensor or fixing a simple wiring issue, restoring your engine's full power.
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Your Next Steps
Step 1: Perform a thorough visual inspection of the boost pressure sensor 'B' and its wiring harness. Look for any signs of damage, corrosion, or loose connections. Wiggle the connector while monitoring live data if you have a scan tool.
Step 2: If the visual inspection doesn't reveal the problem, use a multimeter to test the voltage at the sensor connector. Confirm you have a 5-volt reference signal and a good ground. Then, test the sensor's signal output.
Step 3: If the sensor tests faulty or the wiring is damaged, replace the boost pressure sensor 'B' or repair the wiring. Clear the code and test drive the vehicle to confirm the fix.