When a boost sensor signal falls close to 0 volts, the engine computer knows the circuit has failed. A P0241 code means the turbocharger boost sensor B signal is lower than its allowed range.
This guide explains what pulls the signal low, how to test the reference voltage and wiring, and which repairs fix it.
P0241 Code Breakdown
Every OBD-II code follows the same five-character pattern set by the SAE J2012 standard. Each character narrows down which system has the fault. This table shows what each part of the code tells you.
| Character | Meaning | What It Tells You |
|---|---|---|
| P | Powertrain | The fault is in the engine or transmission systems. |
| 0 | Generic (SAE) code | The definition is the same on every OBD-II vehicle. |
| 2 | Fuel and air metering | The fault involves fuel and air metering, such as injectors, the fuel pump, throttle sensors or boost control. |
| 41 | Specific fault | Turbocharger Boost Sensor B Circuit Low Input |
What the P0241 Code Means
The SAE J2012 standard defines the P0241 code as Turbocharger Boost Sensor B Circuit Low Input. Sensor B is a second boost pressure sensor. It is used on some twin turbo engines, on engines with two charge air paths and on some diesels that measure pressure before and after the intercooler. Check your service manual to see where sensor B sits on your engine.
The sensor gets a 5-volt reference and a ground from the powertrain control module (PCM) and sends back a voltage that rises with pressure, usually between about 0.5 and 4.5 volts. With the engine off, it should read the same as barometric pressure, about 14.7 psi or 101 kPa at sea level.
The PCM uses the reading to control boost through the wastegate or turbo vanes and to set fuel delivery. When it cannot trust the sensor, it usually limits boost and puts the engine in reduced power.
Low input means the signal voltage dropped below the lowest value a working boost sensor B should ever send. That usually points to a lost reference voltage, a signal wire shorted to ground or a sensor that has failed inside.
Symptoms of a Bad Boost Sensor B
Because boost control depends on this sensor, power usually suffers. Common signs of a P0241 code include:
- Check engine light on
- Reduced power or limp mode
- Slow or no turbo boost
- Black smoke on diesels
- Poor fuel economy
- Boost gauge reading wrong or stuck
Some engines run almost normally at light throttle and only show the problem under load, when the PCM needs accurate boost readings the most.
Most Common Causes of the P0241 Code
Low input faults almost always come from an electrical problem:
- Open 5-volt reference. Without its supply, the sensor cannot produce a signal.
- Signal wire shorted to ground. Chafed insulation touching metal pulls the voltage down.
- Failed boost sensor B. An internal short drags the signal low.
- Corroded or loose connector. High resistance on the reference pin lowers the signal.
- Shorted 5-volt reference. Another sensor on the same reference can pull it down.
- PCM fault. Rare.
Tools You Will Need
You can do most of this testing at home with basic tools:
- OBD-II scan tool that shows boost and barometric pressure
- Digital multimeter with back-probe pins
- Boost leak tester or smoke machine
- Sensor-safe cleaner
- Wiring diagram for your engine
How to Diagnose the P0241 Code
Work from the scan tool to the connector, and check for boost leaks before you condemn the sensor.
Check Live Data
With the key on and engine off, look at the boost sensor B reading. It should be close to barometric pressure. Then watch it during a brief, safe acceleration. A reading stuck near 0 or 5 volts confirms a circuit fault.
Check the Reference Voltage
Unplug the boost sensor B and turn the key on. The reference pin should read close to 5 volts. If it reads 0 volts, unplug other sensors on the same reference one at a time. If the voltage comes back, the last sensor you unplugged is shorted.
Check the Signal Wire for a Short
With the battery disconnected and the sensor and PCM unplugged, check the signal wire for continuity to ground. Any continuity means a short. Inspect the wiring where it passes near metal edges and hot parts.
Check for Related Codes
Codes such as P0299 (underboost) or P0106 (MAP range) can point to a shared cause. Fix circuit codes on shared references first, since one shorted sensor can affect several readings.
Repairs That Clear the P0241 Code
Match the repair to what your tests found. Then clear the code and drive under the same conditions that set it.
- Clean or replace the connector if pins are corroded or loose.
- Repair damaged wiring near the intake and turbo, where heat is high.
- Clean the sensor port if oil or soot blocks it.
- Fix boost leaks by tightening clamps and replacing split hoses.
- Replace boost sensor B if it reads wrong at rest or fails electrical tests.
After the repair, clear the codes and compare the key-on reading with barometric pressure again. Then drive and watch desired and actual boost under load. They should track closely, and the engine should pull normally again.
Common Mistakes to Avoid
These mistakes waste money or leave the real fault in place:
- Replacing the sensor without checking the reference voltage
- Missing a shorted sensor elsewhere that drags the shared reference down
- Replacing the sensor without checking for a clogged port
- Buying a sensor with the wrong pressure range for your engine
What Repairs Cost
The cost to fix a P0241 code depends on the cause. This table shows typical ranges for parts and labor.
| Repair | DIY Cost | Typical Shop Cost |
|---|---|---|
| Connector or pigtail | $10 to $40 | $75 to $200 |
| Wiring repair | $10 to $30 | $100 to $300 |
| Boost sensor | $30 to $150 | $150 to $350 |
| Intercooler hose or clamp | $15 to $100 | $100 to $300 |
Most repairs for boost sensor codes are inexpensive. The sensor usually bolts on with one or two screws, so labor is low unless it sits under other parts.
Can You Drive with a P0241 Code?
You can usually drive gently, since most engines limit boost and run in reduced power. Expect slow acceleration, which can make merging and passing unsafe.
Avoid hard acceleration and towing until the fault is fixed. A wrong boost reading can also cause rich running and heavy smoke on diesels.
Related Codes
These codes often show up with this one or point to the same system:
| Code | Meaning |
|---|---|
| P0239 | Turbocharger Boost Sensor B Circuit Malfunction |
| P0240 | Turbocharger Boost Sensor B Circuit Range/Performance |
| P0242 | Turbocharger Boost Sensor B Circuit High Input |
| P0234 | Turbo/Super Charger Overboost Condition |
| P0299 | Turbo/Super Charger A Underboost Condition |
Fixing Turbo Boost Sensor B
A P0241 code means boost sensor B voltage is too low. Lost reference voltage, shorts to ground and failed sensors cause most cases.
- Confirm the low reading in live data.
- Check the 5-volt reference.
- Test the signal wire for a short to ground.
- Replace the sensor only after the wiring tests good.
Frequently Asked Questions
Is the P0241 Code Always a Bad Sensor?
No. A lost 5-volt reference or a signal wire shorted to ground causes many low input codes. Check the reference at the connector before buying a sensor, since a wiring fix costs much less.
Where Is the Turbo Boost Sensor?
It is usually on the intake manifold or on the charge pipe after the intercooler. On many engines, it is combined with the intake air temperature sensor. Your service manual or a parts catalog shows the exact location.
Is the Boost Sensor the Same as the MAP Sensor?
On some engines, yes. The MAP sensor on a turbo engine often doubles as the boost sensor. Other engines have both, with the boost sensor before the throttle and the MAP sensor after it. Check the part number before buying.
How Do I Test a Boost Sensor with a Multimeter?
Back-probe the connector with the key on. The reference should read about 5 volts and the ground close to 0 volts. The signal should match the pressure chart in your service manual, and it should rise smoothly if you apply gentle pressure to the sensor port with a hand pump.
Can a Bad Boost Sensor Cause Black Smoke?
On diesels, yes. If the sensor reports more boost than the turbo is making, the PCM may add fuel for air that is not there. The extra fuel cannot burn fully, so the engine smokes black and fuel economy drops.
Can Oil Clog the Boost Sensor?
Yes. Crankcase vent oil and soot travel through the intake on many turbo engines and can coat the sensor tip. A coated sensor reacts slowly or reads wrong. Cleaning it carefully, or replacing it, often fixes the reading.