P0241 Code: Turbocharger Boost Sensor B Circuit Low

Quick Answer

• What it means: The Powertrain Control Module (PCM) detects an abnormally low voltage signal from the turbocharger or supercharger boost pressure sensor "B".
• Severity: Moderate to High – You can drive it home or to a shop, but the vehicle will likely enter "limp mode" with significantly reduced power.
• Most common cause: A faulty boost pressure sensor, a short to ground in the sensor wiring, or a corroded electrical connector.

What the P0241 Code Means

The official OBD-II definition for P0241 is Turbocharger/Supercharger Boost Sensor "B" Circuit Low.

To put that in plain English: Modern turbocharged and supercharged engines use a boost pressure sensor (also known as a MAP sensor in some configurations) to measure the exact amount of air pressure the turbo is forcing into the engine. The engine computer (PCM) uses this data to adjust fuel delivery, ignition timing, and turbo wastegate operation.

Most boost sensors operate on a 5-volt reference circuit. As boost pressure increases, the sensor's signal voltage sent back to the PCM increases (typically ranging from 0.5V to 4.5V). When code P0241 triggers, it means the PCM is receiving a signal voltage from Sensor "B" that falls below the minimum threshold (often below 0.3V or 0.5V) for a set amount of time. The "Circuit Low" designation almost always points to an electrical issue—such as a short to ground or a completely dead sensor—rather than a mechanical turbo failure.

Common Symptoms

When your engine computer loses accurate boost data, it goes into a self-preservation mode to prevent engine damage. You can expect to experience:

• Check Engine Light: Will illuminate almost immediately after the fault is detected.
• Limp Mode: The PCM will limit engine RPM and cut boost to prevent over-boosting, resulting in a drastic loss of power.
• Sluggish Acceleration: The vehicle will feel incredibly slow to respond to throttle inputs.
• Poor Fuel Economy: Default fuel mapping kicks in, which is less efficient.
• Abnormal Turbo Noises: The wastegate may remain open, changing the exhaust and turbo sound.

Common Causes

Here is what generally triggers the P0241 code, ranked from most to least likely:

1. Faulty Boost Sensor (Sensor B): The internal components of the sensor can fail over time due to heat, vibration, or oil contamination, causing it to output no voltage.
2. Wiring Issues (Short to Ground): Chafed wires touching the engine block or each other can short the signal wire directly to ground, dropping the voltage to zero.
3. Corroded or Loose Connector: Moisture intrusion or a broken locking tab can cause a poor connection at the sensor plug, dropping the signal.
4. Failed 5-Volt Reference Circuit: If the PCM isn't sending the 5V power supply to the sensor, the sensor cannot return a signal.
5. Faulty PCM: Very rarely, the internal circuitry of the engine computer fails and cannot read the sensor data correctly.

How a Technician Diagnoses It

To properly diagnose a P0241 code, an ASE-certified technician will follow a logical electrical testing sequence to avoid unnecessarily replacing a good sensor:

1. Scan and Review Freeze-Frame Data: The technician uses a professional scan tool to verify the P0241 code and check freeze-frame data. This shows exactly what the engine parameters (RPM, load, boost pressure) were when the code set.
2. Visual Inspection: They will closely inspect the wiring harness leading to Boost Sensor "B" for melted insulation, rat damage, or chafing. The connector is unplugged and checked for green corrosion or pushed-out pins.
3. Check the 5-Volt Reference and Ground: With a digital multimeter (DMM), the tech checks the sensor harness. There must be a steady 5-volt power supply from the PCM and a clean ground. If the 5V reference is missing, the problem is in the harness or the PCM, not the sensor.
4. Test the Signal Wire: The technician will jump the 5V reference to the signal wire. If the scan tool suddenly shows maximum boost pressure (around 4.5V+), the wiring to the PCM is good, confirming the sensor itself is the culprit.
5. Sensor Bench Test: A vacuum/pressure pump is applied to the sensor while monitoring its voltage output. A healthy sensor will sweep smoothly from ~0.5V to 4.5V as pressure is applied. If the voltage stays stuck near 0V, the sensor is dead and must be replaced.

Typical Repair Cost

The cost to fix a P0241 code depends on whether the issue is a simple sensor swap or a complex wiring repair. Estimated costs include parts and labor:

• Boost Pressure Sensor Replacement: $150 – $350 (Parts are typically $50-$150; labor is $100-$200).
• Wiring Repair: $100 – $300 (Mostly labor to trace and repair the short or replace the connector pigtail).
• Diagnostic Fee: $100 – $150 (Usually rolled into the repair cost if you have the work done at the same shop).

Can I Keep Driving with this Code?

Technically, you can drive with a P0241 code, but you shouldn't drive it far or ignore it for long. Because the PCM cannot read turbo pressure, it puts the engine into "limp mode" to protect it. You will have severely reduced power, making highway merging or passing dangerous. Furthermore, driving long-term with default fueling parameters can lead to excessive carbon buildup or damage to the catalytic converter. It is best to drive directly home or to a repair facility.

Related Codes

If you have P0241, you might also see these related turbo and boost sensor codes:

• P0240: Turbocharger/Supercharger Boost Sensor "B" Circuit Range/Performance
• P0242: Turbocharger/Supercharger Boost Sensor "B" Circuit High (the exact opposite of P0241, usually an open circuit or short to voltage)
• P0234: Turbocharger/Supercharger Overboost Condition
• P0237: Turbocharger/Supercharger Boost Sensor "A" Circuit Low

Get this scanned at a trusted shop on Repairius.