P2049: first reductant valve control is shorted toward battery supply

P2049 is labeled reductant injector circuit high, bank 1 unit 1. GM's reviewed row defines the electrical mechanism as the dosing valve's low-side control shorted to battery. It is a circuit diagnosis, not a command for a high quantity of DEF injection.

Why “low-side” and “high” are compatible

“Low-side” names the controlled part of the circuit; “high” describes the short-to-supply fault recognized there. The terms do not contradict each other. The hardware power-short interface must indicate a fault, and the associated enable status must be determinate.

The page does not publish a specific external voltage threshold or a wiring-isolation sequence. Its supported conclusion is therefore a qualified hardware power-short indication, not a confirmed failed injector or controller.

Retesting the right condition

Calibration enablement, key-on or engine-running operation, no cranking and battery voltage above 11 volts are required. The diagnostic accumulates 30 failures within 60 samples at a 100-millisecond rate. The reporting class is Type A over one trip.

Confirmation should evaluate the unit 1 power-short diagnostic after it becomes eligible. A result obtained with inadequate battery voltage or indeterminate hardware status does not establish an electrical pass. Dosing performance, pressure and fluid quality remain separate questions unless additional evidence connects them.

This explanation applies only to the documented 2025 GM monitor. Vehicle-specific service information must establish the installed valve and safe electrical procedure before any component-level repair decision is made.

Source: GM monitor, PDF page 776.