Faulty turbocharger/supercharger inlet pressure sensor.; Damaged or corroded wiring or connector at the sensor.; Vacuum or boost leak in the intake system upstream of the sensor.; Clogged or restricted inlet pressure sensor port or tube.; Failed sensor reference voltage or ground circuit.; ECM software issue or internal fault (less common).

DTC codes / P01xx · Fuel and air metering / P012B

P012BTurbocharger/Supercharger Inlet Pressure Sensor A Circuit Range/Performance

P012B indicates that the engine control module (ECM) has detected an out-of-range or performance fault in the circuit for the turbocharger or supercharger inlet pressure sensor, often called sensor A. The ECM compares the sensor's signal against expected values under specific operating conditions and sets the code when the signal does not match the predicted pressure within a calibrated time window.

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 power or limp mode, especially under acceleration or load.
Rough idle or stumbling during light throttle applications.
Poor fuel economy or increased fuel consumption.
Hesitation or delayed turbo boost response.
In rare cases, black smoke from the exhaust due to incorrect fuel delivery.

Common causes, most likely first

Faulty turbocharger/supercharger inlet pressure sensor.
Damaged or corroded wiring or connector at the sensor.
Vacuum or boost leak in the intake system upstream of the sensor.
Clogged or restricted inlet pressure sensor port or tube.
Failed sensor reference voltage or ground circuit.
ECM software issue or internal fault (less common).

How to diagnose and fix it

Perform a visual inspection of the sensor, connector, and wiring for damage or corrosion.
Check for technical service bulletins (TSBs) or software updates for the ECM related to this code.
Use a scan tool to verify live sensor data and compare it to expected values under key-on, engine-off and idle conditions.
Test the sensor's reference voltage and ground circuits with a multimeter to rule out wiring faults.
Inspect the intake system for leaks or restrictions between the air filter and the sensor.
Replace the inlet pressure sensor if testing confirms it is faulty.
Clear the code and perform a road test to verify the repair and ensure the code does not return.

Common misdiagnosis traps for P012B

A dirty or contaminated sensor element can cause a range/performance fault without completely failing, so cleaning the sensor may resolve the issue before replacement.
Intake leaks after the mass airflow sensor but before the turbo inlet can mimic a sensor fault, so always smoke-test the intake system.
The ECM may set P012B due to a faulty barometric pressure sensor or a mismatch between sensor readings, so compare all pressure sensor values.
After replacing the sensor, some vehicles require a relearn or adaptation reset to prevent the code from returning immediately.
Wiring harness chafing near hot components or sharp edges is a frequent hidden cause, so inspect the entire circuit, not just the connector.

Can I keep driving with P012B?

It is generally safe to drive with P012B if the vehicle is not in limp mode, but avoid heavy acceleration or towing until the fault is repaired. Prolonged driving with incorrect pressure readings can lead to poor fuel economy or increased emissions, so schedule a diagnosis soon.

Tools that help

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