P0843: pressure-sensor A high signal does not establish high fluid pressure

P0843 diagnoses a high electrical input from transmission pressure sensor A. The cited CVT row uses raw signal duty cycle above 95 percent and describes a short-to-voltage or open-circuit failure.

Read the signal quantity correctly

The threshold is PWM duty cycle, not a pressure value or a percentage over the normal operating pressure. The source therefore does not support concluding that hydraulic pressure is excessive solely from this code.

The diagnostic accumulates more than 0.3 second of failure in a half-second sample window, updating every 6.25 milliseconds. A momentary boundary crossing and a completed failed window are different evidence. Both battery and run/crank supplies must exceed 9 volts for the specified enabling interval.

Confirm which physical sensor is meant

The electrical row identifies the primary pulley, while the neighboring sensor-A performance row identifies the secondary pulley. That published inconsistency prevents a reliable component-location inference from A alone. Use the exact transmission's service mapping before choosing where to test.

Record raw duty cycle, supply context and test status. Verification should demonstrate valid signal encoding and a passing circuit-high monitor before using the sensor value in pressure-performance comparisons. The table supports both open and voltage-short interpretations but does not uniquely distinguish them, name a connector, or require replacing the sensor. The mapping issue remains flagged for review rather than silently selecting one pulley.

Source and applicability

Documented monitors in gm-2025-03a, model year 2025. These are module/calibration examples; vehicle, engine and transmission applicability must be confirmed independently. GM 2025-03a, page 1133. Neighboring rows documenting the mapping conflict: page 1129.