You may have a wiring issue between the sensor and the ECU. Here is a likely schematic. The two pin intermediate connectors are known to fail. Also check the connector at the ECU for pushed back pins. Be sure you reset the codes correctly. I misread the instructions and was chasing my tail when I had a connector seating problem on the engine speed sensor. Fortunately the Allison was smart enough to get engine speed from the engine off the data bus so I was not stranded.
The oil level sensor is costly to replace. You can use the dipstick as an alternative.
Allison MH4000 info needed