Faulty inlet pressure sensor A.; Short to ground in the sensor signal circuit.; Open or high-resistance ground circuit at the sensor.; Damaged or corroded sensor connector.; PCM internal fault (rare).; Wiring harness damage from heat, chafing, or rodent damage.; Missing 5-volt reference voltage to the sensor.

DTC codes / P01xx · Fuel and air metering / P012C

P012CTurbocharger/Supercharger Inlet Pressure Sensor A Circuit Low

P012C indicates that the powertrain control module (PCM) has detected an abnormally low voltage signal from the turbocharger or supercharger inlet pressure sensor A circuit. This sensor measures the pressure at the compressor inlet, and a low signal typically means the circuit is shorted to ground or the sensor's reference voltage is missing.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms.
Reduced engine performance or power, especially under boost.
Poor fuel economy or rough running if the PCM defaults to a calculated value.
In rare cases, a limp-home mode with limited RPM.
No symptoms besides the warning light in many instances.

Common causes, most likely first

Faulty inlet pressure sensor A.
Short to ground in the sensor signal circuit.
Open or high-resistance ground circuit at the sensor.
Damaged or corroded sensor connector.
PCM internal fault (rare).
Wiring harness damage from heat, chafing, or rodent damage.
Missing 5-volt reference voltage to the sensor.

How to diagnose and fix it

Use a scan tool to verify the code and check live data for the inlet pressure sensor reading.
Visually inspect the sensor and its connector for damage, corrosion, or loose pins.
Measure the sensor's reference voltage (typically 5V) and ground circuit with a multimeter.
Check the signal circuit for a short to ground by measuring resistance to chassis ground.
If the circuit tests good, replace the inlet pressure sensor.
Clear the code and test-drive the vehicle to confirm the repair.
If the code persists, diagnose the PCM and its connections.

What a low inlet pressure signal really means

A low signal often results from a short to ground in the wiring, not a failed sensor, so always check the harness before replacing parts.
The inlet pressure sensor is sometimes confused with the manifold absolute pressure (MAP) sensor, but they serve different purposes and have different circuits.
On some vehicles, a dirty or restricted air filter can cause abnormal pressure readings, though it rarely sets this specific code.
A faulty sensor can cause the PCM to underestimate boost pressure, leading to overboost conditions and potential engine damage if ignored.
The code can be set by a poor ground connection at the sensor, which is often overlooked during diagnosis.

Can I keep driving with P012C?

You can generally drive with this code, but avoid heavy acceleration or towing until it is repaired, as the engine may not manage boost correctly and could suffer damage over time.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.