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Air intakeSeverity Medium: diagnose soon

P0238Turbocharger/Supercharger Boost Sensor "A" Circuit High

What it means

The boost pressure sensor signal voltage is higher than the sensor can normally produce (close to 5 V). Most often the signal wire or the sensor ground is open, or the signal is shorted to a supply voltage.

Symptoms

  • Limp mode with low power
  • Black smoke or poor acceleration
  • Check engine light

Common causes

  • Open signal wire (the ECU's pull-up then reads high)
  • Open or high-resistance sensor ground
  • Signal shorted to the 5 V reference or to battery voltage
  • Failed boost pressure sensor

What to check first

  1. Measure the voltage drop on the sensor ground with the key on (should be under 0.1 V)
  2. Unplug the sensor: the live data should jump to the opposite extreme
  3. Inspect the harness for chafing against other wires or hot parts
Can I drive with P0238? Usually yes for a short distance, but performance or economy may suffer and the fault can get worse. Diagnose it soon.

Generic OBD-II meaning. Manufacturer-specific meanings and checks can differ; always check the service information for the car.

How to test the parts behind P0238

MAP and boost pressure sensorWiring, typical values, multimeter and scope tests

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P0238: questions and answers

What does P0238 mean?

P0238: Turbocharger/Supercharger Boost Sensor "A" Circuit High. The boost pressure sensor signal voltage is higher than the sensor can normally produce (close to 5 V). Most often the signal wire or the sensor ground is open, or the signal is shorted to a supply voltage.

What are the symptoms of P0238?

Limp mode with low power. Black smoke or poor acceleration. Check engine light.

What causes P0238?

Open signal wire (the ECU's pull-up then reads high). Open or high-resistance sensor ground. Signal shorted to the 5 V reference or to battery voltage. Failed boost pressure sensor.

How do you diagnose P0238?

1. Measure the voltage drop on the sensor ground with the key on (should be under 0.1 V) 2. Unplug the sensor: the live data should jump to the opposite extreme 3. Inspect the harness for chafing against other wires or hot parts

Can I drive with P0238?

Usually yes for a short distance, but performance or economy may suffer and the fault can get worse. Diagnose it soon.