P0235 is a generic OBD-II trouble code that indicates a problem with the Turbocharger/Supercharger Boost Sensor A Circuit. The ECM/PCM has detected that the electrical signal from the boost pressure sensor is missing, abnormal, or outside the expected operating range. Because this sensor provides important pressure information used by the engine control system, a fault may affect turbocharger control, engine power, fuel delivery, and emissions. Diagnosis should begin with the sensor wiring, connector, power supply, ground, and signal circuit before replacing the sensor.
Code Specifications
DTC: P0235
Type: Generic OBD-II Powertrain Code
System: Engine / Forced Induction
Component: Turbocharger/Supercharger Boost Sensor A
Circuit: Boost Pressure Sensor Circuit
Monitoring Module: ECM/PCM
Code Category: Sensor Circuit Malfunction
Symptoms of P0235
The MIL may illuminate when the ECM detects the sensor circuit fault.
The engine may enter a protective operating strategy.
Incorrect boost information can affect engine performance.
Boost control may become limited or inconsistent.
Actual boost behavior may not match the expected operating condition.
Incorrect pressure information can affect engine control calculations.
Common Causes of P0235
The sensor may produce an incorrect or unstable signal.
A broken wire can prevent the ECM from receiving the correct sensor signal.
A signal wire shorted to power or ground can create an abnormal voltage.
Corrosion, loose terminals, or poor contact can interrupt the sensor circuit.
Incorrect sensor supply or ground can affect the signal.
Heat, vibration, oil, or mechanical damage can affect the circuit.
A control-module fault is possible but should be considered only after the external circuit has been tested.
Is P0235 Dangerous to Drive With?
P0235 should be diagnosed as soon as practical. The code can affect turbocharger control and engine performance. Short-distance driving may be possible when the engine is operating normally, but continued driving should be avoided if there is severe power loss, abnormal boost, heavy smoke, unusual turbocharger noise, or other serious symptoms.
Common Repairs for P0235
Repair open, shorted, damaged, or high-resistance wiring.
Correct corrosion, loose terminals, damaged pins, or poor electrical contact.
Repair the supply or ground circuit when testing confirms a problem.
Replace the sensor only after confirming that the circuit and reference values are correct.
Correct an ECM/PCM-side circuit problem only after the wiring and sensor have been verified.
P0235 Repair Cost
Repair cost depends on the vehicle and the actual cause. Wiring and connector repairs are generally less expensive than replacing a sensor or diagnosing a control-module problem.
Typical diagnostic cost: approximately $50–$150
Wiring/connector repair: approximately $50–$250+
Boost pressure sensor: approximately $100–$400+
These are general estimates only. Labor rates, vehicle design, parts prices, and manufacturer-specific procedures can significantly change the final cost.
Common Repair Mistakes When Diagnosing P0235
A wiring, connector, power, ground, or signal problem can produce the same code.
Loose or corroded terminals can cause intermittent sensor faults.
The sensor supply, ground, and signal should be verified before condemning the component.
Operating conditions when the fault occurred can help identify an intermittent problem.
Control-module replacement should only be considered after the complete external circuit has been verified.
The repair should be confirmed with live data and a suitable road test.
How to Diagnose P0235
Step 1: Scan for All DTCs
Connect a suitable scan tool and record P0235 along with any other stored, pending, or manufacturer-specific codes. Related sensor or boost-control codes may provide important diagnostic information.
Step 2: Record Freeze Frame Data
Record engine RPM, engine load, vehicle speed, coolant temperature, throttle position, MAP/boost pressure, and other available pressure-sensor parameters. This helps determine when the ECM detected the abnormal condition.
Step 3: Inspect the Sensor and Wiring
Locate Boost Sensor A and inspect the connector and harness for corrosion, water intrusion, damaged insulation, broken wires, loose terminals, or contact with hot or moving components.
Step 4: Check Sensor Power and Ground
Using the vehicle wiring diagram, verify the sensor supply and ground circuits. Do not assume that every boost sensor uses the same voltage or pin arrangement.
Step 5: Check the Signal Circuit
Measure the sensor signal and compare it with the manufacturer's specified range. The signal should respond logically to changes in pressure.
Step 6: Compare Sensor Reading With Actual Conditions
Compare the scan-tool pressure reading with the actual operating condition. At key-on/engine-off, many pressure sensors should report a value reasonably close to atmospheric pressure, but exact specifications vary by system and altitude.
Step 7: Verify the Repair
Repair the confirmed fault, clear the DTC, monitor the boost-pressure data during a controlled road test, and rescan the vehicle to confirm that P0235 does not return.
Where Is the Component That Can Cause P0235 Located?
Boost Sensor A is normally installed in a location where it can measure intake manifold, charge-air, or turbocharger-related pressure. Depending on the vehicle, it may be mounted on the intake manifold, charge-air pipe, intercooler plumbing, or another part of the forced-induction system.
Important: The exact location, connector pinout, and sensor configuration vary by manufacturer, engine, and model year. Always use the vehicle-specific wiring diagram before testing the circuit.
P0235 Signal Flow
Atmospheric / Boost Pressure
│
↓
Boost Pressure Sensor A
│
│ Signal
↓
ECM / PCM
│
├── Processes Pressure Data
│
└── Uses Data for Engine / Boost Control
The pressure sensor converts intake or boost pressure into an electrical signal. The ECM/PCM receives this signal and compares it with the expected pressure and other engine operating parameters. A circuit fault or abnormal sensor signal can trigger P0235.
Deep Live Data & Freeze Frame Test for P0235
Freeze Frame Parameters
- Engine RPM
- Engine Load
- Vehicle Speed
- Coolant Temperature
- Throttle Position
- MAP / Boost Pressure
- Boost Sensor Voltage, if available
- Commanded Boost, if available
What to Monitor
With the engine off and ignition on, compare the pressure reading with reasonable atmospheric pressure. During engine operation, monitor whether the sensor value changes smoothly and logically as engine load and boost change.
If the scan tool shows a fixed, implausible, or rapidly fluctuating value, compare the scan data with the electrical signal at the sensor. This helps separate a sensor problem from a wiring or data-processing problem.
Typical values are not universal. Sensor voltage ranges, pressure values, reference voltages, and acceptable tolerances vary by manufacturer and engine. Use manufacturer-specific specifications whenever available.
After Repair
Clear the DTC, restart the engine, monitor the sensor data, perform a suitable road test, and rescan for stored or pending codes.
Multimeter Test for P0235
A multimeter can be used to verify the electrical circuits of Boost Sensor A. The exact connector pins and expected voltages must be obtained from the vehicle-specific wiring diagram.
- Reference/Power: Verify the specified sensor supply voltage.
- Ground: Perform a ground integrity and voltage-drop test.
- Signal: Measure the signal and compare it with manufacturer specifications.
- Continuity: Check for opens, shorts, and excessive resistance in the harness.
- Connector: Check terminal tension and corrosion.
Do not apply a guessed voltage or pinout to the sensor. Different manufacturers can use different circuit configurations.
Oscilloscope Test for P0235
An oscilloscope can be useful when the boost pressure sensor signal is intermittent, noisy, or difficult to diagnose with a multimeter.
Normal Pressure Sensor Signal
Voltage
│ /
│ /
│ /
│_____/________________ Time
Smooth pressure change
Intermittent / Noisy Signal
Voltage
│ /\/\_/\/\
│ /
│____/________________ Time
Unstable signal
Stuck / Abnormal Signal
Voltage
│────────────────────
│
│
│____________________ Time
Little or no response
These waveform drawings are conceptual. The actual voltage range, waveform shape, and sensor response depend on the specific vehicle and sensor design. Use the manufacturer's waveform or electrical specifications whenever available.
Related DTC Codes
P0235 may appear alongside other turbocharger, supercharger, boost-pressure, or MAP-related codes. Related codes should be diagnosed individually and should not automatically be assumed to have the same cause.
Engine Overboost Condition
Turbocharger/Supercharger Boost Sensor A Circuit Range/Performance
Turbocharger/Supercharger Boost Sensor A Circuit Low
Turbocharger/Supercharger Boost Sensor A Circuit High
Frequently Asked Questions
The most common possibilities include a faulty boost pressure sensor, damaged wiring, connector problems, loss of sensor power or ground, or a signal-circuit fault.
Yes. An open, shorted, damaged, corroded, or high-resistance circuit can cause the ECM to detect an abnormal boost sensor signal.
No. Test the power, ground, signal, wiring, and connector before replacing the sensor.
Yes. The ECM may use a protective strategy that limits engine or turbocharger performance when the sensor signal cannot be trusted.
Limited driving may be possible when the engine operates normally, but the fault should be diagnosed promptly, especially if power loss or abnormal boost symptoms are present.
Monitor the boost-pressure sensor data, verify the electrical signal, perform an appropriate road test, and confirm that the code does not return after rescanning.