P2090: Exhaust camshaft actuator circuit low during powered operation

P2090 identifies an electrical low fault in the bank 1 exhaust camshaft actuator solenoid circuit in the reviewed GM monitor. The dictionary calls this the B camshaft actuator. Here the source specifically describes the high-side driver of the oil-control valve, not a measurement of actual camshaft timing.

What the monitor observes

The controller checks its driver voltage while the output is powered on. A voltage outside the driver's accepted range represents a short-to-ground condition. The table gives a controller design specification of less than 0.5 ohm between the signal and controller ground; it does not present that figure as an instruction to resistance-test an energized circuit.

The diagnostic requires system voltage above 11 V and the ignition in crank or run. It uses 20 failing samples out of 25, sampled every 250 milliseconds. Consequently, one momentary voltage observation is not equivalent to reproducing the stored failure.

How to interpret the evidence

An actuator command, supply voltage and circuit response recorded together are more informative than cam angle alone: this code concerns whether the driver can power its load. A mechanical timing problem cannot be inferred from this electrical result.

The powered-on condition also matters when evaluating an intermittent fault. Evidence collected only while the actuator is inactive may miss the state that the monitor evaluates. Use the vehicle-specific circuit procedure to distinguish the load, wiring and driver; this summary does not identify which one needs replacement.

Source and applicability

This explanation is limited to the documented 2025 GM monitor; its thresholds are not universal vehicle specifications. GM diagnostic table, PDF page 586.