P2842: Rod-four circuit low can mean missing transitions or low duty

P2842 is the electrical-low diagnostic on rod-four position feedback. The source gives two routes: no pulses with the pin below 2 V, or duty cycle below 8%. These describe signal behavior and do not establish that the rod is mechanically at a low point.

Complete the row across both pages

Page 914 starts the pulse-loss branch; page 915 continues the duty-cycle criterion and lists a 150 ms confirmation interval. The associated reference group is VREF2, with P0652/P0653 and controller-voltage faults included in the inhibit list.

The source’s VREF2 enable limits require both above 5.5 V and below 4.5 V. That inconsistency remains unresolved, so this article does not substitute a guessed normal supply window.

A useful verification distinguishes the branches

Capture whether transitions disappear entirely or remain present with too little duty cycle. An average voltage or converted position can conceal that difference. Keep the reference-supply diagnostic state with the capture and resolve exact eligibility through applicable service information. The monitor classifies the input’s failure pattern; it does not by itself identify whether the sensor, harness, connector or controller input caused it.

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 914, GM physical PDF page 915.