P0270: injector 4 low-side voltage remains low while switched off

P0270 checks the injector-4 low-side driver for a short-to-ground pattern. The controller observes low voltage during the driver's off state. The source describes the threshold as impedance between the low-side pin and controller ground at or below 0.5 Ω.

The off-state condition is decisive

Low voltage at a low-side driver cannot be interpreted without knowing whether it is commanded on or off. This monitor specifically evaluates an unexpected low level while off, rather than a normal low level during commanded conduction. The code does not describe low fuel pressure or insufficient injector quantity.

The test requires battery voltage above 11 V, key on, no cranking and at least one second of engine operation. An injection request and the row's output-enable state are also required. It uses four failures out of eight samples at 100 milliseconds each, with Type A, one-trip reporting.

Evidence and verification

Preserve the driver state and fault subtype. A resistance number without the correct circuit isolation is not equivalent to the controller's running diagnostic and can be unsafe to obtain incorrectly.

Verification should show the low-side feedback following the expected off-state behavior through an eligible evaluation. The table does not locate the ground path or prove the injector itself failed. Use vehicle-specific professional electrical tests before any component replacement or high-pressure fuel work.

Source and applicability

GM 04B, PDF page 1131. This explanation covers the documented 2025 monitor. Confirm the vehicle's module, engine and calibration before applying these criteria; the document's vehicle list does not establish this code's applicability to every listed model.