P0240

Universal

Turbocharger Boost Sensor B Circuit Range/Performance

Definition source: General OBD-II reference catalog
Definition verification: Not independently verified for display.
Time: Varies by diagnosis and vehicle | Diagnostic difficulty: Medium
Medium Severity

The engine computer has detected that the signal from turbocharger boost sensor B is outside the range or pattern it expects. This sensor reports boost pressure so the computer can monitor and manage engine operation. Depending on the vehicle and fault, you may notice reduced power or a warning light, or no obvious symptoms.

Report an error with this code

⚠️ Before You Begin (Safety First)

If the vehicle has severe power loss, heavy smoke, unusual turbo or engine noise, or signs of overheating, stop driving when it is safe and arrange an inspection. Avoid hard acceleration until the cause is identified. Turbocharger parts and nearby components can become very hot.

Common Symptoms

  • The check-engine light may come on because the computer has detected an unexpected boost-sensor signal.
  • Reduced engine power or slower acceleration may occur if the computer limits engine output in response to the detected condition.
  • Turbo boost or engine performance may feel inconsistent if the reported pressure does not match actual operating conditions.
  • The vehicle may show no noticeable symptoms, particularly if the signal issue is intermittent or has little effect on operation.

Common Causes

  • Boost sensor B may provide an inaccurate or intermittent pressure signal.
  • A loose, corroded, damaged, or poorly connected sensor connector or wiring may disrupt the signal.
  • A blocked, damaged, or leaking pressure passage or hose may cause the sensor reading to differ from expected boost pressure.
  • A fault elsewhere in the boost or turbocharger system may create pressure readings that appear implausible to the computer.

Diagnostic Steps

  1. Note when the warning light appeared and whether power, smoke, noise, or other symptoms changed; this context can help guide diagnosis.
  2. With the engine off and cool, visually check accessible sensor wiring and connectors for looseness or visible damage. Do not pull on wires or probe terminals without the correct service information.
  3. With the engine off and cool, look for accessible boost-pressure hoses or passages that are visibly loose, cracked, disconnected, or obstructed. Avoid touching hot turbocharger or exhaust parts.
  4. If an OBD scan tool is available, record the stored codes and any available freeze-frame information before clearing codes; this may preserve useful diagnostic context.
  5. Have a qualified technician perform vehicle-specific electrical and boost-system tests if the checks do not reveal an obvious issue or the symptoms are significant.

When to Call a Professional

A technician can review stored codes and live sensor data, check whether the signal is plausible under the conditions recorded, and inspect the sensor wiring, connector, and boost-pressure path. Electrical checks should follow the vehicle-specific service information; the code alone does not confirm that the sensor needs replacement.

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Commonly Asked Questions

Does P0240 prove that boost sensor B has failed?

No. It identifies an unexpected range or performance from the sensor circuit, but wiring, connections, pressure passages, or another boost-system problem can also contribute.

What does boost sensor B do?

It reports boost pressure to the engine computer, which uses sensor information to monitor and manage engine operation. The exact sensor location and naming depend on the vehicle.

Can I keep driving with P0240?

That depends on the symptoms. If the vehicle runs normally, arrange diagnosis soon and avoid hard acceleration. Stop when safe if there is severe power loss, heavy smoke, unusual noise, or overheating.

How is this code diagnosed?

Diagnosis typically compares available sensor data with expected behavior, then checks the sensor circuit and relevant pressure passages or boost-system components using vehicle-specific service information.

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