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P0235 — Turbochargersupercharger Boost Sensor Circuit

Generic OBD-II · all makesPowertrain (engine & transmission)

OBD-II code P0235 indicates a malfunction in the circuit that monitors the turbocharger or supercharger boost pressure sensor. This sensor measures the pressure of the air entering the engine to ensure optimal performance and efficiency, and the code suggests the signal is missing, out of range, or electrically faulty.

Symptoms

What causes it — most likely first

1. Faulty boost pressure sensor

The sensor itself may be damaged, contaminated, or internally failed, causing incorrect or no signal output. This is the most common cause of P0235.

2. Damaged or corroded wiring or connectors

Wiring harnesses leading to the sensor can become frayed, broken, or corroded, disrupting the electrical signal. Connectors may also become loose or contaminated.

3. Vacuum or pressure leaks in the boost system

Leaks in hoses, intercooler pipes, or intake manifold gaskets can cause incorrect pressure readings, leading to a false code.

4. Failed turbocharger or supercharger

Mechanical failure of the forced-induction system (e.g., wastegate stuck open/closed, damaged impeller) can result in abnormal pressure readings.

5. Clogged or restricted intake or intercooler

Blockages in the air intake system or intercooler can cause pressure irregularities, triggering the code.

6. Faulty PCM (rare)

While uncommon, a malfunction in the Powertrain Control Module (PCM) could incorrectly interpret sensor signals or fail to provide proper reference voltage. This is a last-resort diagnosis after all other causes are ruled out.

How it's diagnosed

  1. Retrieve and document all stored trouble codes and freeze-frame data using an OBD-II scanner.
  2. Visually inspect the boost pressure sensor, wiring, and connectors for damage, corrosion, or loose connections. Repair or replace as needed.
  3. Test the boost pressure sensor’s electrical signals (voltage, resistance, or frequency) using a multimeter or oscilloscope, comparing readings to manufacturer specifications.
  4. Check for vacuum or pressure leaks in the intake system, intercooler, and associated hoses using a smoke machine or visual inspection. Repair leaks as necessary.
  5. Inspect the turbocharger or supercharger for mechanical issues, such as a stuck wastegate, damaged impeller, or excessive shaft play. Test boost pressure under load if possible.
  6. If all other components test normal, verify PCM operation by checking reference voltage and ground signals to the sensor. Replace the PCM only if all other causes are eliminated.

Code facts & related codes

SystemPowertrain (engine & transmission)
StandardizationSAE generic — identical on every make
Related codesP0230 — Fuel Pump Primary CircuitP0231 — Fuel Pump Secondary Circuit LowP0232 — Fuel Pump Secondary Circuit HighP0233 — Fuel Pump Secondary Circuit IntermitteP0234 — Turbochargersupercharger Overboost ConP0236 — Turbochargersupercharger Boost Sensor

Frequently asked

Can I drive with a P0235 code?

Driving with P0235 may result in reduced engine power, poor fuel efficiency, or potential long-term damage to the turbocharger or engine. It is advisable to diagnose and repair the issue as soon as possible.

Is P0235 always caused by a bad boost sensor?

No. While a faulty boost sensor is the most common cause, issues like wiring damage, vacuum leaks, or turbocharger failure can also trigger this code. Always perform a thorough diagnosis before replacing parts.

Will replacing the PCM fix P0235?

Replacing the PCM is rarely the solution for P0235. The PCM should only be considered after all other potential causes—such as the sensor, wiring, or turbocharger system—have been ruled out.

Why does my car go into limp mode with P0235?

Limp mode is a protective feature that limits engine power when the PCM detects a critical fault, such as abnormal boost pressure. This prevents potential engine or turbocharger damage until the issue is resolved.