What Does P0235 Mean?
The turbocharger/supercharger boost pressure sensor A circuit has a general malfunction. This sensor provides critical boost pressure feedback to the ECM for controlling wastegate position and fuel delivery. Without reliable boost data, the ECM cannot safely manage boost pressure. The driver may notice reduced power, limp mode activation, or the engine defaulting to atmospheric (no boost) operation.
Common Causes
35%
Failed boost pressure sensor A providing no signal or erratic output
25%
Wiring fault (open, short, or high resistance) in the boost sensor circuit
20%
Corroded or damaged boost sensor connector
12%
Blocked or leaking vacuum/pressure reference line to the sensor
8%
ECM 5V reference circuit fault affecting the sensor supply
Diagnostic Steps
1
Read the boost pressure sensor A PID at key-on engine-off — it should read approximately atmospheric pressure (14.5–14.8 psi / ~100 kPa). A reading of 0 or maximum indicates a circuit fault.
2
Verify the 5V reference voltage at the sensor connector with the sensor unplugged — should read 4.9–5.1V. Also confirm a solid ground (under 0.5 Ω to battery negative).
3
Check the pressure reference hose to the sensor for blockage, cracks, or disconnection. Blow through the hose to verify it's clear. Oil or moisture in the hose can affect readings.
4
Measure the sensor output voltage at idle (should reflect vacuum) and at boost (should increase with pressure). Compare to manufacturer's voltage/pressure table.
5
If the sensor is integrated into the intake manifold, check for intake leaks near the sensor mounting that could affect the pressure reading.
Estimated Repair Cost
$80 - $350
Parts + labor, varies by vehicle and location
The turbocharger/supercharger boost pressure sensor A circuit has a general malfunction. This sensor provides critical boost pressure feedback to the ECM for controlling wastegate position and fuel delivery. Without reliable boost data, the ECM cannot safely manage boost pressure. The driver may not...
The most common cause of P0235 (Turbocharger Boost Sensor A Circuit Malfunction) is: Failed boost pressure sensor A providing no signal or erratic output
Typical repair costs for P0235 range from $80 to $350, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Drive gently. Without accurate boost pressure data, the ECM may not detect an overboost or underboost condition. Most ECMs will enter a safe/limp mode limiting power. Avoid hard acceleration and repair promptly, as unmonitored boost is a risk factor for engine damage.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0235 to identify the root cause.
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Quick Info
Category
Powertrain
System
Turbocharger / Supercharger System
Difficulty
Type
Generic (SAE)
Recommended Tools
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