P0277: injector 6 stays high during an on command

For the documented GM strategy, P0277 means that injector 6's low-side driver circuit shows high voltage during the on state. The controller interprets this signature as a short toward the power supply.

Separate high voltage from high fuel quantity

The word “high” qualifies the control circuit. It does not establish overfueling, rail pressure or a learned injection correction. The source describes a low-impedance connection, 0.5 ohm or less, between the low-side pin and controller power. A technician must use the applicable electrical diagnosis to locate that condition; the code is not a component-level verdict.

This is the opposite command phase from the documented P0276 check, which looks for low voltage when injector 6's driver is off. That distinction changes which command-and-response relationship matters in a captured trace.

Validate an eligible operating period

The table requires battery voltage above 11 V, a running engine for at least one second, no cranking and an injection request. It filters the result through four failed samples out of eight at 100 ms intervals and lists Type A, one-trip reporting.

A successful verification therefore needs an eligible injection event and normal circuit behavior, rather than merely a cleared fault memory. Vehicle-specific instructions remain necessary for circuit identification and safe access.

Source and applicability

2025 GM 25OBDG04B diagnostic parameter tables; the cited monitor only. Vehicle, engine and calibration applicability must be confirmed separately. These tables describe detection logic, not a complete repair procedure or a component replacement verdict. gm-2025-04b, PDF page 1136.