Fuel and air

P012B — Turbo/Supercharger Inlet Pressure Sensor Range/Performance

Severity: medium Drive with care, to a shop

What P012B means

The engine control module compares the signal from the turbo or supercharger inlet pressure sensor with what it expects for the current engine speed, load and ambient pressure. P012B is stored when the reading is out of range or does not agree with other sensors. Without accurate pressure data, the module cannot control boost properly.

Symptoms

  • Check Engine light on
  • Reduced power and sluggish acceleration
  • Limp mode
  • Poor fuel economy
  • Rough idle or hesitation
  • Unusual turbo whistle or noise

Possible causes

  1. Failed turbo/supercharger inlet pressure sensor
  2. Damaged wiring or corroded connector at the sensor
  3. Intake or boost air leak near the sensor
  4. Clogged or damaged air filter
  5. Turbo actuator fault or sticking variable geometry mechanism
  6. Rarely, a faulty engine control module

How to diagnose

  1. Read codes and freeze frame data and look for other boost or pressure codes
  2. Inspect the sensor connector and harness for corrosion, chafing, poor contact, opens or shorts to ground
  3. Test sensor power, ground and reference voltage with a multimeter
  4. Compare the sensor reading in live data with ambient pressure with the engine off
  5. Inspect the air filter, intake hoses, clamps and intercooler for cracks and leaks
  6. Check the intake system and vacuum lines for leaks
  7. Compare specified and actual boost under load
  8. Check actuator movement across its full range, including the variable geometry mechanism

Common fixes

  • Replace the inlet pressure sensor
  • Repair damaged wiring or the connector
  • Replace hoses and clamps to stop air leaks
  • Replace the air filter
  • Repair or replace the turbo actuator; update software or replace the control module only if confirmed faulty

Questions and answers

Can I drive with a P012B code?

For a short time, usually, but expect reduced power. Get it diagnosed soon to avoid stressing the turbo.

What most often causes P012B?

Most often it is the pressure sensor itself or its wiring and connector. Also check for air leaks in the intake and the condition of the air filter.

Can I just clear the code?

You can clear it, but it will return if the cause is not fixed. Find the fault first.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.