Fuel and air

P012C — Turbo/Supercharger Inlet Pressure Sensor Circuit Low

Severity: medium Drive with care, to a shop

What P012C means

The engine control module uses the turbocharger or supercharger inlet pressure sensor to calculate boost and fuel delivery. P012C sets when the sensor signal voltage falls below the expected range. Typical reasons are a failed sensor, an open or grounded signal wire, or a lost reference voltage or ground.

Symptoms

  • Check Engine light on
  • Reduced power and sluggish acceleration
  • Limp mode
  • Poor fuel economy
  • Hesitation or rough idle
  • Possible unusual turbo noise

Possible causes

  1. Failed turbo inlet pressure sensor
  2. Damaged wiring or a poor connector contact
  3. Open sensor ground or missing 5V reference
  4. Turbo actuator or position sensor fault
  5. Sticking variable geometry mechanism
  6. Charge-air or vacuum leak
  7. Engine control module fault (rare)

How to diagnose

  1. Scan for codes and freeze-frame data, clear the code and see if it returns
  2. Inspect the sensor, connector and harness for chafing, corrosion, oil and heat damage
  3. With the engine off, check live data: inlet pressure should be near atmospheric
  4. Test reference voltage, ground and signal wire at the connector using the wiring diagram
  5. Check the signal wire for a short to ground
  6. Compare commanded and actual boost under load
  7. Inspect hoses, intercooler piping and vacuum lines for leaks
  8. Check actuator movement through its full range

Common fixes

  • Replace the inlet pressure sensor
  • Repair the wiring harness or replace the connector
  • Restore the sensor ground or reference circuit
  • Fix charge-air or vacuum leaks
  • Clean or replace the turbo actuator or variable geometry mechanism
  • Reprogram or replace the control module (last resort)

Questions and answers

Can I drive with P012C?

Briefly and carefully, such as to a shop. Expect reduced power, and the engine will not manage boost properly with bad sensor data.

What most often causes P012C?

Usually the pressure sensor itself or a wiring or connector problem. Check the harness and sensor supply first before replacing parts.

Does P012C mean the turbo is bad?

Usually not. The code points to the sensor circuit. If the wiring and sensor test fine, check the turbo actuator and boost leaks.

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.