P2091: Exhaust camshaft actuator circuit high and the driver-off check

P2091 is the bank 1 exhaust camshaft actuator solenoid circuit-high diagnosis in the reviewed GM source. Although the catalog uses the B camshaft label, the documented component is the exhaust cam phaser oil-control valve and its high-side driver.

Electrical meaning

The strategy and malfunction text describe checking driver voltage when the output is powered off. Voltage outside the permitted range then indicates a short-to-power condition. That is different evidence from a camshaft failing to reach its commanded angle: the controller is identifying an electrical state that should not remain present when power is removed.

The source specifies system voltage above 11 V, crank or run ignition, and 20 failing samples out of 25 at 250 milliseconds per sample. Its less-than-0.5-ohm figure is a driver design specification for a short to controller power, not a general service resistance limit.

A source inconsistency that matters

The same row's enable column says the output driver is on, which conflicts with the driver-off strategy. The diagnostic principle is clear, but the exact command-state enabling logic needs the applicable service information before reproducing the test.

Record commanded output state and electrical feedback together. A high reading during an intentional on command does not, by itself, establish the off-state fault described here. Also retain cam timing codes separately: P2091 does not prove a phaser, timing chain or oil-pressure failure. Repair verification should demonstrate that the electrical monitor completes without recurrence under the correct calibration-specific conditions.

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 587.