[77newell]

According to the Allison manual for the HT and MT series electronic transmissions, the "check trans" light has 12vdc on one terminal and the ground side is connected to ground through a relay triggered by the ECU grounding the coil of that relay. The power to the coil comes from 12vdc supplied through an oil pressure switch on the engine. The relay is held open when there is both oil pressure and the ECU providing ground (neither the "check trans" switch nor ECU sensed anomalies causing the coil ground to open).

On my 93 coach the relay is the 3rd from the top in a stack of relays in the compartment containing the Allison ECU.

You said there was no power to the "check trans" bulb. It is designed to always have power and only the ground side is controlled to turn it off/on. In my 93 coach that power comes from a circuit that supplies power to other things in the dash.

There is a relay that sends the "fast idle" signal to the engine ECU by grounding the signal wire. On my coach this relay is mounted in the front panels by the copilot's feet. The "fast idle" switch uses 12vdc to turn on the "fast idle".

The idle issue and the step issue seemed to appear and disappear at the same time. I suspect that a loss of power to the "fast idle" switch and the step occurred at the same time. I don't know enough about the wiring to offer a suggestion for how that could occur and then self correct, maybe it's just magic.