P0E38: converter voltage B low is a separate channel diagnosis

P0E38 is DC/DC converter voltage-sensor B low in the cited ECM. The controller evaluates raw converter actuator voltage 2 below 1 volt as a short-to-ground circuit signature.

Separate channel 2 from battery supply

The monitor requires battery voltage at least 6.60 volts. That prerequisite shows why a below-one-volt channel-2 report should not be described as a battery below one volt. It is also distinct from the voltage-1/A low diagnostic; a good first-channel reading cannot validate the second channel.

The recorded failure depends on 320 low samples out of 400 at a 12.5-millisecond loop rate. A single recovered reading after the event does not reveal the preceding sample history, and a single brief low sample does not prove the whole decision completed.

An active sensor supply is required

This 03A example selects a sensor-bus-relay enable route, requiring relay on and relay fault false. The row's alternative Global-B run/crank-or-accessory route is architecture dependent. Confirm the selected path before interpreting absence of a fresh failure as successful verification.

Retain the raw voltage-2 reading, battery voltage and power-state context. The code does not identify an internal converter part or prove the converter's complete output has collapsed. Verification should establish a passing enabled low-input monitor using the specific vehicle procedure. Avoid assigning a hybrid/high-voltage architecture or performing internal electrical tests solely from the generic converter name.

Source and applicability

Documented monitors in gm-2025-03a, model year 2025. These are module/calibration examples; vehicle, engine and transmission applicability must be confirmed independently. GM 2025-03a, page 448.