P0236

Turbocharger Boost Sensor A Circuit Range/Performance

P0236 is a generic OBD-II powertrain diagnostic trouble code: Turbocharger Boost Sensor A Circuit Range/Performance. 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.

Code
P0236
Group
Powertrain
System
Turbo/Boost
Severity
Warning (MIL on, possible limp mode)
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What P0236 means

P0236 is a rationality fault set when the PCM or ECM determines that the turbocharger/supercharger boost pressure sensor 'A' is reporting a value that is implausible given other engine parameters. Unlike P0237 or P0238 (which detect an out-of-range signal voltage), P0236 is triggered when the sensor voltage is within the normal electrical range (typically 0.5–4.5 V) but the actual pressure reading it implies does not correlate with what the ECM expects based on throttle position, engine speed, MAF reading, and barometric pressure. For example, if the sensor reports positive boost pressure while the engine is idling with the throttle closed and the turbo not yet spooling, the ECM flags a performance fault.

The boost pressure sensor 'A' is most commonly a three-wire MAP-type sensor mounted on the intake manifold or intercooler outlet, downstream of the turbocharger and intercooler. It supplies a voltage proportional to absolute pressure (typically 1 V at atmospheric and rising toward 4.5 V at maximum boost). Contamination from oil blow-by, carbon deposits, or a kinked vacuum/pressure hose can cause the sensor to read incorrectly without the signal voltage leaving the normal electrical range, making P0236 a common result of intake fouling rather than a wiring failure.

When P0236 is stored, the ECM may substitute a fixed boost pressure value and limit turbo output to protect the engine, resulting in a noticeable power reduction or limp mode. Clearing the code without addressing the root cause will typically result in the fault returning within one to two drive cycles.

Common causes

Most-frequently reported root causes when P0236 is logged.

  • 1
    Boost sensor contaminated with oil or carbon deposit from blow-by, causing it to read incorrectly while still producing an in-range voltage.
  • 2
    Kinked, cracked, or disconnected pressure hose between the intake manifold and the boost sensor port, giving the sensor an incorrect reference pressure.
  • 3
    Boost sensor diaphragm degraded or partially ruptured, resulting in a sluggish or offset pressure reading.
  • 4
    Air leak downstream of the MAF (split intercooler hose, loose clamp, cracked intake pipe) causing the MAF and boost sensor to report conflicting air mass values.
  • 5
    High-resistance or intermittently open reference-voltage or ground wire reducing the sensor output range and shifting its calibrated curve.
  • 6
    ECM/PCM input circuit degradation — analog-to-digital converter issues causing misreading of a correct signal.
  • 7
    Actual turbocharger mechanical fault (worn compressor wheel, damaged turbine, sticking VNT vanes) producing boost levels inconsistent with commanded pressure.

Symptoms drivers notice

Check Engine Light illuminated, sometimes flashing under load.
Reduced engine power and sluggish acceleration — noticeable turbo lag or absence of boost.
Engine entering limp mode (boost and fuelling limited by ECM substituting a default pressure value).
Possible unusual turbocharger noise (whistling or whining) caused by altered boost control behaviour.
Decreased fuel economy due to the ECM running on a fixed, non-optimal boost estimate.

How to diagnose P0236

A typical diagnostic flow when this code is present.

  1. 1
    Scan for all codes and record freeze frame data; note engine speed, load, and MAF values at the time the fault set.
  2. 2
    View live sensor data and compare the boost sensor voltage at idle (should be approximately 1.5–2.0 V at atmospheric) against the barometric sensor or MAP sensor reading.
  3. 3
    Inspect the boost sensor pressure port and hose for cracks, kinks, oil contamination, or disconnection.
  4. 4
    Perform a smoke or pressure test on the intake tract downstream of the MAF to locate any boost leaks that could explain a MAF/boost sensor discrepancy.
  5. 5
    Back-probe the sensor signal wire and verify reference voltage (~5 V), ground, and signal output move proportionally when pressure is applied.
  6. 6
    Clean the sensor port and hose of any oil fouling, clear codes, and road test under load to check if the fault resets.
  7. 7
    If electrical checks pass and no leaks are found, evaluate turbocharger mechanical condition (boost pressure actual vs. commanded via WGDC).

Related powertrain codes

Frequently asked questions

Why does P0236 set instead of P0237 or P0238?

P0237 and P0238 fire when the signal voltage itself goes below or above the sensor's electrical limits (roughly 0.5 V or 4.5 V). P0236 fires when the voltage is electrically valid but the pressure it implies is inconsistent with other engine data. A contaminated sensor or a boost leak typically lands in P0236 territory because the sensor still responds, just inaccurately.

Can an oil leak cause P0236?

Yes. Excessive crankcase blow-by or a leaking turbo oil seal can coat the boost sensor's pressure port or sensing element with oil, effectively shifting the sensor's reading. Cleaning the sensor port and the hose often resolves the fault without replacing the sensor.

Will the car go into limp mode with P0236?

On many vehicles, yes. When the ECM cannot trust the boost pressure reading, it substitutes a conservative fixed value and caps boost to protect the engine and turbocharger. This typically feels like a significant power loss, particularly above 2,000 rpm.

Is P0236 specific to turbocharged diesel engines?

No. The code applies to any forced-induction engine — petrol or diesel, turbocharged or supercharged — that uses a boost pressure sensor. It is most commonly seen on turbocharged diesel and direct-injection petrol engines where oil contamination of the intake is more prevalent.

Disabling P0236 in software

RaceTune can permanently disable P0236 — 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.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

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.

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