P2839: Rod-two high requires pulse-loss or excessive-duty evidence

P2839 is the high electrical check for rod-two position feedback. The controller looks for no pulses with pin voltage above 3.5 V, or for duty cycle above 92%. The continuation page is needed to see the duty-cycle route and the 150 ms confirmation interval.

A high phase is not a static high fault

Sampling a valid pulse during its high phase does not establish pulse loss. Conversely, a signal can keep pulsing but still exceed the permitted duty cycle. Those two possibilities require different waveform evidence even though they share the DTC.

The original table’s reference-supply enables are contradictory, specifying above 5.5 V and below 4.5 V for VREF1. They are not corrected by assumption here. Listed inhibiting codes cover reference-supply and controller-voltage faults.

Verification that keeps the distinction

Retain pulse activity and duty cycle with the exact rod-two channel and supply diagnostic state. A plausible position display may conceal an electrically rejected signal. Confirm the calibration’s real enable window through service information before using the printed limits. This source identifies a fault pattern but does not prove that the sensor, wiring or input electronics is the component requiring replacement.

Document scope and source

2025 GM 25OBDG07A Part 2 documented monitor only; its application-matrix filename join is unresolved. No model, engine or universal calibration applicability is inferred. These figures explain the cited controller logic, not a vehicle-specific repair instruction. Match the vehicle’s service information before applying them.

GM physical PDF page 912, GM physical PDF page 913.