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DtBt · 06-24-2015, 04:31 PM

The other day I noticed the "Check Trans" warning took about 20 seconds after starting to go out. Always before it always went out immediately. The only code on the shifter was 22-14. According to VMSpc there was a TRN SID 151 14 unknown component special error.
I checked the 22-14 and found it to be input speed sensor. I first reseated and cleaned the sensor connector. After that the "Check Trans" warning went out immediately like always before and VMSpc erro was gone yet the shifter code persisted. I checked further:
The sensor read 315 ohms and the leads each had 19Kohms to ground and 38Kohms to each other. I replaced the sensor but the code is persistent even after a reset. I checked the cabling for signs of rodent or other damage. None found. I reseated the TCM connectors.
If the transmission is not getting engine speed it certainly cannot function so I wonder if-
a. it is smart enough to pick up engine speed from the engine.
b. The signal from the sensor is somehow out of spec yet functional.
The motorhome drives and shifts normally. I honestly don't remember if I ever checked for codes before.

How should I proceed? I plan to buzz the cable but have not found the pinouts on TCM end.

dbarton291 · 06-25-2015, 07:32 AM

Did you try to clear the code? Enter diagnostic mode and hold the mode button for a few seconds. A power reset won't clear the codes. They are stored in an EEPROM.

DtBt · 06-25-2015, 12:44 PM

Yea I did that several times and the code persists. I did obtain the pinouts for the sensor at the TCM and the resistance reading is identical to the reading across the new sensor. My assumption now is there might be a loose connection in the cable or connector that only occurs when subject to vibration of the engine running. I am aware the connectors on the sensors can fail. The other possibility is a bad TCM. In any event I plan to ignore the problem until I get a chance to consult with an Allison Tech as it runs and shifts normally.

DtBt · 07-24-2015, 01:45 PM

Reseating the connector actually solved the problem I believe. We left home for a 2500 mile trip a couple of days after replacing the engine speed sender. The code kept showing up when I checked it previously during the trip. I called Allison and the guy I got said bring it in to an Allison shop and was not interested in any details. Today I read carefully the Allison Shifter Codes and Diagnostic pdf. It said only active codes were reset holding the mode button in until the light flashes three times. The inactive codes require the mode button to be held in for 10 seconds. I was going to try the 10 second button today but the code was gone. I'm assuming the inactive code finally aged out due to ignition cycles.