P0842: pressure-sensor A low input is a PWM circuit fault

P0842 is pressure-sensor A circuit low. The cited CVT table detects raw pressure-sensor duty cycle below three percent and interprets it as a ground-short signature, with controller hardware limitations affecting discrimination of an open condition.

Duty cycle is not pressure

The three-percent boundary describes the signal encoding. It is not three percent of normal hydraulic pressure and cannot be converted directly into kPa from this row. A low duty-cycle code therefore does not by itself prove the transmission has low mechanical pressure.

The detection specification includes less than 0.5 ohm to ground or greater than 200 kilohms to ground in the hardware-dependent interpretation. Those are descriptions of diagnostic capability, not instructions for resistance measurement on an energized sensor circuit.

Scope and mapping limitation

This electrical row calls the sensor the primary-pulley sensor, but the nearby P0841 sensor-A performance row names the secondary pulley. Confirm the actual vehicle mapping before selecting a sensor or harness branch; the source family is internally inconsistent on that label.

The failure must exceed 0.3 second in a 0.5-second sample window, with battery and run/crank voltage above 9 volts for the listed enable interval. Verification should show a legal PWM signal and a passing electrical monitor under adequate supply conditions. The code does not prescribe a sensor replacement or establish that a pressure-performance diagnosis is valid before this electrical issue is resolved.

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 1132. Neighboring rows documenting the mapping conflict: page 1129.