P0847: pressure-sensor B low PWM can have overlapping circuit interpretations

P0847 detects a low signal from transmission pressure sensor B. In the cited CVT electrical row, raw duty cycle below three percent is the relevant boundary. The monitor concerns the signal circuit, not a measured low hydraulic-pressure limit.

Hardware affects fault discrimination

The table describes a ground-short diagnosis and includes both low impedance to ground and an open-like high-impedance specification where controller hardware cannot distinguish the signature. Consequently, P0847 does not universally prove a literal shorted wire to ground.

Failure must exceed 0.3 second within a 0.5-second window. Battery and run/crank voltage each must exceed 9 volts for the specified enabling interval. A low observation outside those supply conditions is not enough to establish a completed enabled test.

Resolve the pulley identity first

This electrical row calls the sensor the secondary-pulley sensor. The nearby P0846 sensor-B performance row instead names the primary pulley. That source inconsistency means B alone cannot locate the component for this article.

Record raw duty cycle and actual controller/sensor mapping before selecting the appropriate circuit diagnosis. Verification should establish a legal signal and a passing low-circuit monitor; an apparently reasonable calculated pressure can be less useful if it is derived from invalid or substituted input. The table does not give a safe energized resistance test, a connector location or a mandatory sensor replacement. Physical mapping remains a review item.

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 1137. Neighboring rows documenting the mapping conflict: page 1134.