Setting Up A Transmission Code for Output Speed Sensor
This is an Allison 3000 Series Automatic Transmission in a 1997 Thomas Pusher School Bus. I did a demo fault in the video to show you what happens when a code develops ….which in this case is a output speed sensor code. I made this code happen by unplugging the output speed sensor connector at the back of the transmission.
Once there is no communication to the transmission ECU or TCU the bus will only move forward in first gear. I actually had a service call in the winter time where a big clump of ice had formed on the connector harness and pulled it out of the socket. If you get a call from an operator who says the transmission is stuck in first gear the output speed sensor may be at fault. An ohm meter check of the sensor should be around 350 ohms.
Using The Shift Pad to Retrieve Codes
With the ignition on you can retrieve transmission codes. All you have to do is press the two arrow keys at the same time as shown in the video. There will be four digits shown 2 at a time. The display flashes the numbered codes continuously. Hit the Mode button to see if there is more than one code and continue hitting the mode button until the display shows “hyphens” flashing on the display.
Clearing Transmission Codes Using The Shift Pad
Once the code has been repaired (or in this case the output speed sensor is plugged back in) you just have to press the mode button until you hear two beeps from the shift pad. This will clear the code and everything will go back to normal operation. The demo I did in the video is similar to an actual code situation. Since this transmission is a WTEC II it can be checked with a ProLink reader as an alternative.