P0340: Bank 1 camshaft Sensor A pulses are missing

The cited GM P0340 monitor evaluates missing pulses from Bank 1 camshaft position Sensor A. It includes starter-based timers, running-engine checks and pulse counting referenced to a synchronized crankshaft. The generic circuit title does not identify a physical sensor location for every engine.

Starting and running are evaluated differently

While cranking, the table uses time since the last cam pulse or time spent cranking without one, with crank pulses or valid airflow providing corroboration. A running path looks for fewer than four pulses over more than three seconds.

Other paths examine cam activity over defined crankshaft event windows. Those require crankshaft synchronization and no active crank-sensor fault. A missing cam result cannot be interpreted confidently if the crank reference used to evaluate it is itself invalid.

What a useful capture includes

Record starter state, cam pulse activity and crank synchronization together. If the engine restarts normally, preserve the original timing information rather than assuming the circuit is now proven good. An intermittent pulse loss can recover before inspection.

The monitor supports investigating the Sensor A signal path, but it does not distinguish a sensor defect from its circuit or target solely by code. Verification should exercise the affected start or run condition and confirm pulses remain present during an eligible monitor. A single displayed cam angle is not equivalent to a completed pulse-presence check.

Source and applicability

This explanation is limited to the 2025 GM 25OBDG03A monitor on page 267. Its thresholds are calibration examples, not universal specifications. Confirm the vehicle, engine and controller procedure before applying them.