P2127: Accelerator pedal sensor 2 has a low or open signal

P2127 reports the second accelerator pedal position channel below its allowed range in the reviewed GM monitor. The generic sensor E label corresponds here to APP2. The source explicitly includes a low short or an open circuit, so the code does not identify one exclusive wiring failure.

The second channel has its own scale

APP2 fails below 6.50% of a five-volt reference scale. That threshold is not a pedal-travel percentage and should not be borrowed from APP1. The two pedal channels have separate electrical limits, which matters when interpreting simultaneous recordings.

Run/crank voltage must be greater than 6.41 V. The row names P0697 in its reference-fault exclusion, although its prose describes the reference number inconsistently. Use the vehicle's actual circuit information to identify the reference supply rather than choosing a wire from that label alone.

An intermittent drop can count

This monitor is capable of recognizing intermittent and continuous faults. The listed criteria are 19 failing counts out of 39 or 14 continuous counts, sampled every 12.5 milliseconds. A brief dropout can therefore be relevant even if APP2 returns to its normal level before a later inspection.

The useful question is whether APP2 remains electrically plausible while the monitor is enabled. Preserve reference-fault status and supply voltage alongside the signal trace, then follow the applicable pedal-circuit diagnosis. P2127 does not, by itself, establish a throttle-motor defect or mandate replacement of the complete pedal assembly.

Source and applicability

This explanation is limited to the documented 2025 GM monitor; its thresholds are not universal vehicle specifications. GM diagnostic table, PDF page 599.