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P0237 – Turbocharger Boost Sensor A Circuit Low (OBD2)

P0237 means "Turbocharger Boost Sensor A Circuit Low". The voltage the control unit measures in the boost pressure sensor circuit is below the permitted minimum. For a sensor this usually means the signal wire is shorted to ground or the reference voltage is missing; for an actuator, that its control wire is shorted to ground.

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P0237 quick summary

Fault codeP0237
MeaningTurbocharger Boost Sensor A Circuit Low
SystemPowertrain (Engine & Transmission)
VehiclesGeneric OBD2
SeverityMedium
Can I drive?Usually yes, in limp mode. With an overboost code, avoid full throttle – excessive boost can damage the engine and turbo.
Repair cost€30 – €1,500

How the boost pressure sensor works

The boost pressure sensor measures the pressure the turbocharger produces so the engine control unit can regulate boost and protect the engine; P0234 means boost has exceeded the safe limit.

The boost pressure sensor sits in the charge air pipe or intake manifold after the intercooler, often combined with an air temperature sensor. It works like a MAP sensor with a wider range: a 5 V reference, ground and a signal that rises with pressure.

The control unit compares the measured boost with the target. If the signal is electrically out of range, implausible, or boost goes above the safe limit (overboost, P0234), it reduces power to protect the engine and turbo. Sensor B codes refer to a second sensor on engines with two turbochargers or two measuring points.

Oil mist from the crankcase ventilation and turbo seals often contaminates the sensor; boost leaks, sticking wastegates or vanes and faulty control solenoids cause range and overboost codes.

On VAG vehicles (VW, Audi, Škoda, Seat, Cupra), VCDS and older VAG testers can show this code as the five-digit VAG code 16621 (P0237). Both numbers mean the same fault.

Symptoms of P0237

  • Limp mode, loss of power
  • Check Engine light on
  • Surging power or sudden power cut under acceleration (overboost)
  • Black smoke
  • Turbo or boost control codes alongside

Most common causes of P0237 (most likely first)

Mechanic's Pro Tip

If boost and barometric pressure differ by more than about 50 mbar with the engine off, the boost sensor is faulty. If they agree and the code persists, look at the turbo control instead.

  1. 1.Signal or control wire shorted to ground

    Most likely

    Look for chafed insulation where the harness touches the engine, exhaust brackets or body edges.

  2. 2.Missing 5 V reference or supply voltage

    An open reference wire or a shorted sensor elsewhere on the same reference circuit can pull it down.

  3. 3.Internal short in the boost pressure sensor

  4. 4.Oily or contaminated boost sensor

  5. 5.Failed boost pressure sensor

  6. 6.Wiring fault or 5 V reference problem

  7. 7.Sticking turbo vanes or wastegate (overboost)

Step-by-step diagnostic guide

  1. 1

    Read codes and compare pressures

    Read all codes. With the engine off, the boost sensor should read the same as the barometric pressure.

  2. 2

    Measure the signal voltage

    With the ignition on and the boost pressure sensor plugged in, back-probe the signal wire. Then unplug it and check the reference/supply and ground wires separately.

    Multimeter: Signal near 0 V = short to ground or no reference. Reference wire: about 5 V with ignition on. Signal wire to ground with connector unplugged: no continuity.

  3. 3

    Inspect and clean the sensor

    Remove the sensor, check it for oil and clean it carefully with electrical contact cleaner.

  4. 4

    Check reference, ground and signal

    Measure the 5 V reference and ground and watch the signal rise smoothly with boost.

    Multimeter: Key on, engine off: equal to barometric pressure (about 1,000 mbar near sea level).

  5. 5

    Log specified vs actual boost

    During a full-load acceleration, compare specified and actual boost. Actual boost overshooting the target points to a sticking wastegate or vanes.

  6. 6

    Repair and verify

    Replace the sensor or fix the boost control fault, clear codes and repeat the test drive.

Frequently asked questions

Can I keep driving with P0237?

Usually yes, in limp mode. With an overboost code, avoid full throttle – excessive boost can damage the engine and turbo.

How much does it cost to fix P0237?

Typical repair costs are 30 € – 1500 €, depending on the cause and the vehicle. The most common fixes are: signal or control wire shorted to ground; missing 5 V reference or supply voltage; internal short in the boost pressure sensor. Always confirm the cause with the tests above before buying parts.

What causes overboost (P0234)?

Usually a wastegate or VTG vanes that do not open, a faulty boost control solenoid or a cracked vacuum hose. Less often a faulty boost sensor reading too high.

Is the boost sensor the same as the MAP sensor?

On many turbo engines yes – the MAP sensor in the intake manifold measures boost. Some engines have both.

What is the difference between P0237 and similar codes?

P0237 belongs to a group of codes for the same component that differ in the type or location of the fault: P0234 – Engine Overboost Condition; P0235 – Turbocharger Boost Sensor A Circuit Malfunction; P0236 – Turbocharger Boost Sensor A Circuit Range/Performance; P0238 – Turbocharger Boost Sensor A Circuit High; P0239 – Turbocharger Boost Sensor B Circuit Malfunction; P0240 – Turbocharger Boost Sensor B Circuit Range/Performance. The tests on this page apply to the whole group; the type of fault tells you where to start.

Related fault codes

This guide is for information only. Working on vehicles can be dangerous — if you are unsure, have the car checked by a qualified mechanic. Values can differ between model years; always check the manufacturer's repair information.