P0242 is a generic OBD-II powertrain trouble code indicating that the ECM/PCM has detected a voltage signal from the Turbocharger/Supercharger Boost Sensor "B" circuit that is higher than the expected range.
The term "Circuit High" primarily describes an electrical signal condition. It does not automatically mean that the turbocharger or supercharger is producing excessive boost pressure. A high sensor signal can result from a faulty pressure sensor, signal wire shorted to voltage, poor ground, reference-voltage problems, connector damage, or an actual pressure condition that the ECM considers abnormal.
OEM / Manufacturer Note
P0242 is a generic SAE-style DTC, but the exact sensor identified as Boost Sensor B, connector pinout, operating voltage, diagnostic threshold, and sensor location vary by manufacturer and engine. Always use the correct factory wiring diagram and specifications for the vehicle being diagnosed.
P0242 Causes
Electrical Causes
- Faulty boost pressure sensor B
- Signal wire shorted to voltage
- Damaged or incorrectly routed wiring
- Corroded or loose connector terminals
- Poor sensor ground
- Incorrect reference voltage
- Open or high-resistance circuit
- Rare ECM/PCM fault
Possible Pressure-System Causes
- Abnormally high intake or boost pressure
- Boost-control malfunction
- Wastegate or actuator problem
- Damaged pressure hose or plumbing
- Intake or charge-air system problem
P0242 Symptoms
- Check Engine Light or MIL illumination
- Reduced engine power
- Poor acceleration
- Hesitation during acceleration
- Incorrect boost-pressure readings
- Turbocharger or supercharger performance problems
- Limp-home or reduced-power mode
- Possible poor fuel economy
- Abnormal boost behavior on some vehicles
P0242 Severity
Medium to High. The severity depends on how the vehicle responds to the incorrect boost-pressure information. If the engine has major power loss, uncontrolled boost, abnormal turbocharger noise, excessive smoke, or other serious symptoms, avoid heavy-load driving and diagnose the problem promptly.
If the vehicle operates normally with only the Check Engine Light illuminated, limited driving may be possible, but the fault should still be diagnosed soon.
Faulty Component Responsible for P0242
The primary component monitored by this DTC is the Turbocharger/Supercharger Boost Pressure Sensor B and its electrical circuit.
However, P0242 does not prove that the sensor itself has failed. The ECM/PCM can detect the same condition when the signal circuit, ground, reference circuit, connector, or boost-pressure system has a problem.
Where Is Boost Sensor B Located?
The exact location varies by vehicle. Boost Sensor B may be installed on the intake manifold, charge-air pipe, intercooler piping, turbocharger pressure plumbing, or another location used by the manufacturer to measure intake/boost pressure.
Vehicles with multiple pressure sensors may identify them as Sensor A and Sensor B. Therefore, do not replace a sensor simply because it is the first pressure sensor you find. Confirm its identity using the vehicle-specific service information.
How to Repair P0242
- Repair damaged or shorted signal wiring.
- Repair loose, corroded, or damaged connector terminals.
- Restore the correct sensor ground.
- Repair the reference-voltage circuit when necessary.
- Replace Boost Sensor B if testing proves the sensor defective.
- Repair damaged boost-pressure hoses or charge-air plumbing.
- Repair confirmed wastegate, actuator, or boost-control problems.
- Diagnose the ECM/PCM only after the sensor and circuits have been properly tested.
Common P0242 Repair Mistakes
- Replacing the turbocharger based on P0242 alone
- Replacing the boost sensor without testing its wiring
- Confusing a high electrical signal with actual high boost pressure
- Failing to check the sensor ground
- Failing to verify the reference voltage
- Using the wrong sensor pinout
- Ignoring other stored or pending DTCs
- Failing to inspect the boost-control system
- Not clearing the DTC and performing a verification drive
P0242 Repair Cost
Approximately $50–$150+
Approximately $50–$300+
Approximately $80–$300+
Cost varies significantly by vehicle and failed component.
These are general estimates rather than fixed prices. Parts availability, labor rates, vehicle design, and the actual cause of P0242 can significantly change the final repair cost.
How to Diagnose P0242
1. Scan the Vehicle
Use an OBD2 scanner to retrieve stored, pending, and manufacturer-specific codes. Record the freeze-frame data before clearing the codes.
2. Check Boost Sensor B
Locate the correct sensor and inspect the sensor body, connector, terminals, and wiring. Look for corrosion, oil contamination, broken terminals, damaged insulation, or loose connections.
3. Inspect the Signal Circuit
Because P0242 indicates a high signal condition, check whether the signal wire is shorted to the reference-voltage circuit or another voltage source. Also check for wiring damage and abnormal resistance.
4. Check the Sensor Ground
A poor ground can cause incorrect sensor operation. Test the ground circuit using the manufacturer's recommended voltage-drop or resistance procedure.
5. Verify Reference Voltage
Many analog pressure sensors use a reference voltage of approximately 5 volts, but this is not universal. Verify the correct value using the factory service information.
6. Test the Sensor Signal
Measure the signal voltage and compare it with the manufacturer's specification. A signal that remains abnormally high despite normal pressure conditions can indicate a faulty sensor or electrical fault.
7. Monitor Live Data
Use the OBD2 scanner to monitor the pressure parameter reported by Boost Sensor B. Compare the reading with engine load, throttle position, atmospheric pressure, and actual boost behavior where supported.
8. Inspect the Boost System
Check the turbocharger or supercharger plumbing, intercooler pipes, intake hoses, pressure lines, wastegate system, and boost-control components where applicable.
9. Compare Commanded and Actual Boost
If the vehicle provides these parameters, compare commanded boost with actual boost. This can help determine whether the problem is an electrical sensor issue or a genuine boost-control problem.
10. Clear and Retest
After repairing the confirmed fault, clear P0242 and perform a controlled road test. Confirm that the boost sensor signal responds correctly and that the DTC does not return.
P0242 Signal Flow
On many vehicles, the boost pressure sensor uses three main circuits: reference voltage, ground, and signal. The sensor converts pressure into an electrical signal that the ECM/PCM uses to evaluate engine load and boost operation.
Typical Electrical Testing
Reference
Verify the specified reference voltage at the sensor connector. Do not assume that every vehicle uses exactly the same reference voltage.
Ground
Check the sensor ground for a reliable electrical connection and excessive voltage drop.
Signal
Monitor the signal and compare it with the manufacturer's specified pressure-to-voltage relationship. Many analog sensors operate within a broad range such as approximately 0.5–4.5 V, but this is only a general reference.
Important: A generic voltage range should never replace the manufacturer's specifications. Sensor characteristics and diagnostic thresholds differ between vehicle platforms.
OBD2 Scanner and Live Data
An OBD2 scanner can help identify whether the reported pressure is plausible. Useful parameters may include Boost Pressure, MAP, Intake Pressure, Engine Load, Throttle Position, Commanded Boost, and Actual Boost, depending on the vehicle.
If the sensor reports an extremely high pressure value while the engine is at conditions where that pressure is impossible, an electrical signal problem should be investigated before replacing mechanical turbocharger components.
Can P0242 Be Caused by a Bad Turbocharger?
A turbocharger or boost-control problem can contribute to abnormal pressure readings, but P0242 alone does not prove that the turbocharger is defective. Electrical testing should be performed before replacing expensive turbocharger components.
Can You Drive With P0242?
Limited driving may be possible if the vehicle operates normally, but avoid heavy acceleration if there is severe power loss, abnormal boost behavior, unusual turbocharger noise, smoke, or other serious symptoms.
Vehicle-Specific Notes
The exact Boost Sensor B location, connector pinout, sensor characteristics, reference voltage, signal range, and ECM diagnostic threshold are vehicle-specific. Always verify the correct information for the exact make, model, engine, and year.
Related Codes — Reference Only
The following are separate DTCs associated with turbocharger/supercharger boost sensing or control. They are not alternate definitions of P0242.
Turbocharger/Supercharger Boost Sensor B Circuit
Turbocharger/Supercharger Boost Sensor B Circuit Range/Performance
Turbocharger/Supercharger Boost Sensor B Circuit Low
Turbocharger/Supercharger Boost Sensor A Circuit Low
Turbocharger/Supercharger Boost Sensor A Circuit High
Turbocharger/Supercharger Overboost Condition
P0242 FAQ
Is P0242 a generic OBD-II code?
Yes. P0242 is a generic powertrain diagnostic trouble code, although the exact sensor configuration and diagnostic procedure vary between manufacturers.
Does P0242 always mean the boost sensor is bad?
No. The signal circuit, ground, reference circuit, connector, wiring, and boost-pressure system can all contribute to this DTC.
What should I check first for P0242?
Start with the stored codes and freeze-frame data, then inspect Boost Sensor B and its connector and wiring. Next verify the sensor ground, reference voltage, and signal circuit.
Does a high P0242 signal mean high turbo boost?
Not necessarily. P0242 describes a high electrical signal from the sensor circuit. The actual boost pressure must be evaluated separately using live data and the vehicle's diagnostic specifications.
Should I replace the turbocharger for P0242?
No. Test the sensor and its electrical circuit first. Replacing a turbocharger without confirming a mechanical failure can result in an unnecessary and expensive repair.