P281B: pressure-control solenoid H electrical control path is open

P281B is the open-circuit code for pressure-control solenoid H in the cited 25OBDG04B controller family. The row maps H to nine- or ten-speed torque-converter control, an eight-speed T93 default valve, or CVT mode-valve B. Exact transmission identification is essential before testing.

How an open path is recognized

The driver compares voltage feedback with internal circuit thresholds corresponding to an open condition. The specification is associated with signal-to-controller-ground impedance above 200 kilohms. It does not publish a universal coil-resistance test or authorize measuring resistance on a powered circuit.

Failure time must exceed 0.30 seconds within a sample period exceeding 0.50 seconds, updated every 6.25 ms. Battery voltage must be between 9 V and 32 V for more than one second. An eligible power state, enabled calibration and energized mapped high-side driver are also prerequisites. The entry is Type A, one trip.

Diagnostic distinction

A converter that slips hydraulically and an electrically open control path are different findings. Preserve the electrical report and driver state before evaluating pressure or slip symptoms. If the relevant high-side driver is off, the monitor may not yet provide a valid circuit result.

Verification should show that this qualified open-circuit check completes after repair. The summary does not locate a broken wire or prove that an entire solenoid or valve-body assembly must be replaced.

Source and application limits

This explanation covers the cited 2025 GM monitor. Confirm the vehicle and calibration in its service information before applying these limits; inclusion in this file does not establish model compatibility. GM diagnostic parameters, PDF page 2297.