Cause
Faulty turbocharger inlet pressure sensor
The sensor measuring pressure going into the compressor, ahead of the turbocharger — not the boost coming out of it, which is the confusion this part invites. It sits between the air filter and the turbo in a region at or slightly below atmospheric, because the compressor pulls a depression as it draws air.
So it functions as a restriction gauge more than a pressure gauge. The module compares it against barometric pressure, and a growing difference means the intake is being choked. That is why a blocked air filter, a collapsed intake hose, a snow-packed grille or a nest in the airbox all set faults against this sensor while it works perfectly — it is reporting a restriction nobody has looked for.
Eliminate the intake before replacing the part. The decisive check is at rest: with the engine off this sensor must read barometric and agree with the manifold and barometric sensors. Three sensors that should match and one that does not is the answer, and it takes seconds.
Turbocharger performance codes commonly follow a fault here rather than accompanying it. The module computes the compressor's pressure ratio from this sensor, so while it is untrustworthy the turbocharger cannot be judged — and those codes usually clear with this one.
Typically an easy fix. Often worth checking before paying anyone to look.
Codes this can cause (6)
Codes where this is a likely explanation first, rather than merely a possible one.
- P012A Turbocharger/Supercharger Inlet Pressure Sensor A Circuit Likely for this code Moderate
- P012B Turbocharger/Supercharger Inlet Pressure Sensor A Circuit Range/Performance Likely for this code Moderate
- P012C Turbocharger/Supercharger Inlet Pressure Sensor A Circuit Low Moderate
- P012D Turbocharger/Supercharger Inlet Pressure Sensor A Circuit High Moderate
- P2374 Turbocharger/Supercharger Inlet Pressure Sensor B Circuit Moderate
- P2375 Turbocharger/Supercharger Inlet Pressure Sensor B Circuit Range/Performance Moderate
Information, not instruction
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