Medium and Heavy Trucks
Have Truck Repair Questions? Ask an Expert
Hi my name is***** will be glad to try to help. Are you getting any fault codes? Click this link for the procedure and let me know what comes up for codes. The second link is a troubleshooting guide depending on what codes you get there will be test info for each code.
Fault code retrieval
Thanks for the update. Try disconnecting the batteries for 5-10 minutes and then see if it will reset the TCM. some have been successful shifting F to R etc a few times to get it to engage. Possible causes are worn clutch brake and or clutch, loss of air on trans shifter, bad sol valve or XYZ shifter, or faulty TCM ( computer)
Thanks for the update. Ive known some to be successful letting the truck roll of on an incline to get it to engage but if not check the clutch and clutch brake, XYZ shifter, air pressure to the trans, and lastly the TCM
The engine ECM and transmission TCM both communicate this data so you would have to study a schematic to identify what pins on the ECM and TCM pass that signal and in some way supply that pin with the correct voltage to trick the ECM. I do not recommend doing this as it is a safety issue and could potentially cause damage to the modules if the wrong voltage is applied unfortunately....