Bought a 2005 cummins automatic 2500 heavy duty with 57K mi in 2014, off the lot had a few shifter problems, didn't know it was in park, alarm would sound etc, had it adjusted, seems OK for 40K miles now. Bought a Smarty Junior trying to get mileage up from 16 but no luck with a dozen different settings. Can make it worse for sure and turns the truck into a rocket ship, amazing. All the while sometimes shifting 2nd to 3rd would hang up but letting up accelerator would shift. Seemed OK, a couple weeks ago pulling a trailer with a ton weight, suddenly would not shift. I tried manual shift, no help, put it in 4x4 and it did shift, got home. After disconnecting to return the truck wouldn't shift. I set it back to stock with smarty and tried several new smarty settings, still stuck. back to stock and to the dealer. So if its limp mode there is not dash light flashing. Dealer finds no codes. But notices throttle actuator does not calibrate when key is on, apparently no signal from ECM. So checking to see if computer sees any codes. They wanted $850 to change out throttle actuator, looks a little over priced both on the part and 2 hrs labor with no clear diagnosis I said not yet. So holding until we figure out why no codes. Forums say could be throttle actuator or the governor solenoid, both normally have codes. One forum said bad ground back to ecm, corroded wire connector. ?? Could the smarty have corrupted ecm? I did upgrade smarty when I first got it 2 years ago.

 

After a month at the dealer. Figured out it was not the throttle actuator. Demonstrated ecm could see other codes by disconnecting air intake sensor so ecm was OK. Demonstrated power was getting to actuator. Declined work until we could prove what was wrong since no codes. Chrysler engineering (2 weeks) devised a test. Disconnect throttle actuator, and remove from trans and set aside, turn key to cycle so ecm sends the signal, allows the system to reset. Reconnect actuator and repeat if the actuator calibrates its OK, remount. They dropped the trans pan, not much metal after 100Kmi, bands were "very loose". Replaced solenoid governor but it seemed good, replaced accompanying electronic valve assemble and that cleared the pressure profile seems it was faulty, replaced filter, adjusted bands, cleared ecm. All good runs like new. Key learning was that no-codes just means you have to get the right diagnostic, that saved me $850. They recommend adjusting bands every 60K. The utube videos for replacing governor and valve make it an easy fix and you can save $350.