P0E37: converter voltage B performance depends on operating mode

P0E37 compares converter actuator raw voltage 2 with ECM run/crank voltage. It is the documented DC/DC voltage-sensor B performance monitor, with an absolute mismatch greater than 2 volts as the displayed criterion.

The second channel has its own comparison

A passing voltage-1 reading does not establish that voltage 2 agrees with the ECM reference. The useful record contains raw voltage 2, run/crank voltage and operating mode together. A difference can exist while either individual number appears superficially plausible.

In bypass mode, the sample decision is 320 failures in 400. During auto-cranking stabilization it is eight failures in sixteen; both use a 12.5-millisecond loop. The mode therefore changes how quickly the same mismatch can satisfy the sampling criterion.

Keep architecture and event limits explicit

The 03A and 04B examples select different enable branches, sensor-bus relay versus Global-B run/crank/accessory logic. Both require battery voltage at least 6.60 volts. The additional auto-crank-event count has contradictory wording, so an exact event-count rule is not claimed.

Verification should assess the second channel in the relevant operating mode after resolving the vehicle-specific cause. A normal bypass comparison alone does not cover the stabilization path. This code is not proof of battery failure or a particular converter topology. Follow the professional electrical procedure for that vehicle rather than probing internal converter hardware from this summary.

Source and applicability

Documented monitors in gm-2025-03a, gm-2025-04b, model year 2025. These are module/calibration examples; vehicle, engine and transmission applicability must be confirmed independently. GM 2025-03a, page 446. GM 2025-04b, page 665.