P0872: Pressure sensor C low has a clear voltage path and an unclear supply window

P0872 is the low-circuit code for transmission pressure sensor C. In this GM TCM the channel is the transmission system-pressure sensor. The useful established evidence is an electrical signal below range, not a direct conclusion that hydraulic pressure is low.

The input boundary is documented

The row gives signal voltage below 220 millivolts, 30 millivolts of hysteresis and at least 150 milliseconds of confirmation. Battery voltage must be above 8.75 and below 18 volts, outside cranking and STOP state.

However, the VREF2 enable cells simultaneously print greater than 5.5 volts and less than 4.5 volts. The original PDF confirms those incompatible bounds. The strategy sentence also incorrectly describes a high-voltage check. Neither inconsistency is silently repaired here.

Keep electrical and hydraulic conclusions separate

P0882/P0883 and reference faults P0652/P0653 are listed as disabling conditions. Preserve those statuses along with the pressure-sensor signal; they affect whether the ordinary monitor can run.

A low input cannot establish actual system pressure without the correct sensor transfer function and circuit verification. The source does not locate the fault within sensor, wiring or controller. Obtain the applicable service specification to resolve the supply window before reproducing the test. The supported interpretation remains a low system-pressure input, with explicit limits on the incomplete enable logic.

Source and applicability

This explanation covers the cited GM monitor, not every vehicle carrying this code. The application-matrix filename does not resolve cleanly to this file, so no model or engine fitment is assigned. GM diagnostic table, PDF page 907.