P0235
Turbocharger Boost Sensor A Circuit MalfunctionP0235 is a generic OBD-II powertrain diagnostic trouble code: Turbocharger Boost Sensor A Circuit Malfunction. It is logged by the engine control unit when the turbo/boost monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0235 means
P0235 — Turbocharger/Supercharger Boost Sensor 'A' Circuit — is set when the ECU detects that the signal from the intake manifold boost pressure sensor (often called a MAP or boost sensor) is outside the expected range or is not responding plausibly to engine load changes. This is a sensor circuit fault, not a boost control fault; the code does not mean the turbocharger is over- or under-boosting, only that the ECU cannot trust the sensor reading.
The boost sensor typically outputs a 0–5 V analogue signal proportional to intake pressure, or communicates digitally on some platforms. Faults include an open or shorted signal wire, a damaged sensor, a missing 5 V reference or ground from the ECU, or a cracked vacuum/pressure hose between the manifold and the sensor port that causes an implausible reading. On turbocharged diesel and petrol engines, the ECU relies on this signal to calculate fuelling, EGR rate, and turbo boost targets — incorrect data forces it into a fallback (limp) map.
Related codes P0236–P0238 indicate the sensor signal is in range but stuck high or low; P0235 is the general circuit plausibility fault. Always rule out sensor circuit problems before assuming a turbocharger mechanical issue.
Common causes
Most-frequently reported root causes when P0235 is logged.
-
1
Faulty boost/MAP pressure sensor producing an out-of-range or erratic voltage output.
-
2
Open, shorted, or high-resistance signal wire between the sensor and the ECU.
-
3
Missing or incorrect 5 V reference voltage supplied by the ECU to the sensor.
-
4
Open sensor ground circuit causing the signal to float outside normal operating range.
-
5
Cracked, disconnected, or blocked pressure hose between the intake manifold and the sensor port.
-
6
Corrosion or moisture ingress at the sensor connector causing intermittent contact.
-
7
Oil contamination inside the pressure port blocking the sensor diaphragm on diesel engines.
Symptoms drivers notice
How to diagnose P0235
A typical diagnostic flow when this code is present.
-
1
Read all DTCs with a scan tool; check live boost sensor data — a reading stuck at 0 kPa, 5 V, or an implausible value at idle confirms a circuit fault.
-
2
Inspect the pressure hose or port between the intake manifold and sensor; a loose or cracked hose often causes P0235 without any electrical fault.
-
3
Check the sensor connector for corrosion, pushed-back pins, or moisture; clean and reseat as needed.
-
4
With ignition ON (engine off), measure the 5 V reference and ground at the sensor connector using a multimeter.
-
5
Measure the signal voltage at idle and under throttle snap; an unresponsive or flat signal suggests a failed sensor or broken signal wire.
-
6
Inspect the wiring harness back to the ECU for chafing, particularly near turbo heat sources.
-
7
Substitute a known-good sensor if wiring checks out; clear the code and retest under load before declaring the repair complete.
Related powertrain codes
- P003A — Turbocharger/Supercharger Boost Control A Position Exceeded Learning Limit
- P003B — Turbocharger/Supercharger Boost Control B Position Exceeded Learning Limit
- P0045 — Turbocharger/Supercharger Boost Control A Circuit/Open
- P0046 — Turbocharger/Supercharger Boost Control A Circuit Range/Performance
- P0047 — Turbocharger/Supercharger Boost Control A Circuit Low
- P0048 — Turbocharger/Supercharger Boost Control A Circuit High
Frequently asked questions
Will my turbo be damaged if I drive with P0235?
Not directly from this code, but driving in limp mode long-term can mask other issues. More importantly, if the ECU is not accurately reading boost it cannot properly control EGR or fuelling, which can cause running problems or increased emissions over time.
Is P0235 the same as an overboost or underboost fault?
No. P0235 is a circuit plausibility fault — the ECU cannot read the sensor reliably. Overboost (P0234) and underboost (P0299) mean the sensor is working but boost pressure is outside acceptable limits.
Can a vacuum/boost hose cause this code?
Yes. A cracked or disconnected pressure hose to the sensor is one of the most common causes. The sensor may be electrically perfect but reading ambient air pressure instead of manifold pressure, which looks like a stuck or implausible value to the ECU.
My boost sensor is new but the code came back — why?
Check the 5 V reference and ground circuit at the connector before replacing again. A damaged wire or corroded ECU pin will destroy a new sensor's readings just as readily as the old one.
Disabling P0235 in software
RaceTune can permanently disable P0235 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
Got P0235 in your scan?
Upload your ECU file — we'll identify the exact software version and confirm whether a disable is available for your car.
Upload your file