P0240 — Turbocharger Boost Sensor B Circuit Range/Performance

What does P0240 specifically identify?

P0240 identifies a range or performance fault in the circuit used to monitor turbocharger boost sensor B. The condition may be caused by the sensor, its wiring, or an abnormal boost-control condition.

Can the vehicle still be driven with P0240?

Driving is best limited until P0240 is diagnosed if the engine remains stable and boost readings are normal. Avoid heavy acceleration, and stop driving if the boost reading is unrealistic or warning lights appear.

Where is boost sensor B located?

The exact position of boost sensor B varies by vehicle, so use the manufacturer wiring information rather than assuming a universal location. Its connector, signal wire, and powertrain control module pin can confirm the correct component.

Should boost sensor B be replaced just because P0240 is present?

No. P0240 can also result from corroded connectors, damaged wiring, a poor ground, or turbo boost-control problems. Confirm the live signal, circuit voltages, and commanded-versus-actual boost before replacing the sensor.

P0240 is a powertrain diagnostic trouble code that indicates the engine control module has detected an abnormal signal from the secondary turbocharger boost sensor. When this code appears, it means the ECM has identified that the voltage or frequency signal from boost sensor B falls outside the expected range for the engine's current operating conditions. The "range/performance" designation tells you the sensor is sending a signal—the wiring checks out—but that signal does not align with what the control module expects to see based on throttle position, engine speed, and load data.

Modern turbocharged engines depend on accurate boost pressure feedback to manage power delivery and protect the turbocharger from damage. When P0240 triggers, the ECM recognizes a mismatch between the commanded boost level and what the sensor is actually reporting. The fault will not illuminate the check engine light after a single bad reading—the module requires the fault to occur repeatedly under specific driving conditions before it stores the code and activates the warning lamp. The freeze frame data saved alongside P0240 shows engine load, RPM, coolant temperature, and vehicle speed at the moment of failure, which tells you exactly what conditions to reproduce during testing.

The secondary boost sensor, often called the "B" sensor to distinguish it from the primary MAP sensor, monitors intake manifold pressure after the turbocharger's compressor outlet. When this reading drifts high or low, the ECM cannot accurately control the wastegate or boost control solenoid, resulting in poor performance, excessive exhaust smoke, or limp-home operation.

Common Symptoms of P0240

• Whistling, hissing, or siren-like noises from the engine bay under boost
• Noticeable loss of engine power and sluggish acceleration
• Dark black smoke from the exhaust during hard acceleration
• Vehicle enters limp-home mode with reduced power output
• Check Engine Light remains illuminated on the dashboard
• Reduced fuel efficiency compared to normal driving

What Causes P0240?

• Degraded or drifting turbocharger boost sensor B (most frequent culprit)
• Boost leak in intercooler piping, cracked hoses, or loose clamps
• Incorrect sensor calibration following a module software update or battery disconnect
• Worn or failing turbocharger with insufficient boost development
• Stuck or faulty wastegate and malfunctioning boost control solenoid
• Damaged vacuum lines or actuator hoses related to boost regulation
• Clogged intake tract or restricted exhaust (clogged DPF or catalytic converter)
• Mechanical fault upstream that the sensor correctly reports
• Intermittent electrical connections or corrosion at the sensor connector

How to Diagnose P0240

1. Connect an OBD2 scanner, confirm P0240 is stored in the ECM, and record the freeze frame data showing engine conditions at the time of failure.
2. Check for related diagnostic trouble codes—other boost-related or sensor codes often point to the root cause. Review manufacturer TSBs for your specific make and model, as many boost system faults have documented factory solutions or software calibrations.
3. Perform a thorough visual inspection of the wiring harness and connectors feeding the turbocharger boost sensor B. Look for chafed insulation, broken wires, corrosion, or connectors that are not fully seated.
4. Compare the live boost sensor B reading against specifications or a correlated sensor (such as the primary MAP sensor) while the engine operates under the freeze frame conditions.
5. Pressurize the intake system and check for boost leaks—cracked intercooler hoses and loose clamps are the most frequently encountered mechanical issue.
6. Use the scanner to command the boost control solenoid and verify that the wastegate responds correctly with audible or physical movement.
7. Clear the code, complete a drive cycle that replicates the freeze frame conditions, and verify that P0240 does not return.

Repair Options with Costs

• Repair boost leak (hoses, clamps, intercooler): $100–$400
• Replace boost control solenoid or actuator: $200–$600
• Replace turbocharger boost sensor B: $150–$400
• Replace turbocharger assembly: $1,200–$3,500

How Much Does It Cost to Fix P0240?

Repair costs hinge entirely on which component has failed. Here are typical scenarios for P0240 at independent shop rates, including parts and labor in USD. A boost leak repair runs $100–$400 and is the least expensive fix. Replacing the boost control solenoid or actuator typically costs $200–$600. A failed turbocharger boost sensor B replacement generally runs $150–$400. At the high end, a complete turbocharger replacement—including labor—falls between $1,200 and $3,500. Overall, fixing P0240 can cost anywhere from $100 to $3,500 depending on the root cause. An accurate diagnosis before purchasing parts is the smartest first step, because the most expensive scenario is rarely the first place to look.

Can You Drive with P0240?

Severity: Caution. P0240 typically forces the engine into limp-home mode, severely limiting power and boost. Driving gently and avoiding high loads reduces the risk of immediate damage. However, ignoring a boost fault can allow the turbocharger to overheat, deliver inconsistent power, or suffer premature wear. A failed turbocharger replacement is far more expensive than addressing the sensor or leak that caused the code in the first place. Drive conservatively to a repair facility as soon as possible.

Related OBD2 codes

• P0200: Injector Circuit Malfunction
• P0201: Injector Circuit Malfunction - Cylinder 1
• P0202: Injector Circuit Malfunction - Cylinder 2
• P0203: Injector Circuit Malfunction - Cylinder 3
• P0204: Injector Circuit Malfunction - Cylinder 4
• P0205: Injector Circuit Malfunction - Cylinder 5