Diagnostic article Generic OBD-II
P2C12: Exhaust camshaft sensor A must not be confused with intake sensor B
Learn the two separate letter designations in P2C12 and the energized open-circuit monitor they identify.
Read before applying this article
Documented application
2025 GM 25OBDG03B documented monitor only. Vehicle, engine and calibration applicability must be confirmed from the matching service information; no model fitment is inferred.
The code alone does not identify a failed part or establish that a vehicle is safe to drive. Confirm the vehicle, reporting module and applicable service procedure.
P2C12’s description contains two different labels: the B camshaft designation and position sensor A. In this GM table, the monitored system is the exhaust camshaft profile mechanism and its A position-sensor channel. Confusing the camshaft letter with the sensor letter could direct an investigation to the wrong circuit.
The row describes electrical integrity under power
The controller compares voltage with its own open-load thresholds while the output is on. The listed classification represents impedance above 200 kΩ toward controller ground. This is not a direct test of exhaust-pin travel or cam timing.
The adjacent P2C13 performance monitor evaluates an unexpected Hall-state sequence. Thus, a circuit-open result and a present-but-implausible movement signal remain separate kinds of evidence even though they concern the same functional channel.
Verify the intended output and operating state
The output must be commanded on, supply above 11 V, ignition in crank or run and diagnostic enablement active. Four failures out of five samples establish the stated result; one-trip reporting is a different layer of confirmation.
Preserve the exhaust system identity, A channel and actual on command before comparing electrical readings. The table does not provide a physical sensor location or identify which part of the path is interrupted. The applicable circuit procedure is needed before replacing a sensor, actuator or controller.
Source and applicability
2025 GM 25OBDG03B documented monitor only. Vehicle, engine and calibration applicability must be confirmed from the matching service information; no model fitment is inferred. These criteria explain controller logic, not a complete repair procedure. 25OBDG03B, PDF page 909. 25OBDG03B, PDF page 910.
Article source documents
Source checks describe how the text was prepared; they do not certify a diagnosis or confirm compatibility with every vehicle using this code.
Original code reference
Dictionary definition
B Camshaft Profile Actuator Position Sensor A Circuit Bank 1
This definition retains its original catalog scope. The article above is limited to its explicitly documented application.
Reference scope
Generic OBD-II definition.
A manufacturer label does not establish the model, year, engine or module to which a diagnosis applies. Read the safety and diagnostic limits.
Definition source
- DTC Database: pinned community code definitions
Source checked · MIT