This is when things become difficult without a scanner that can read the type of codes related to the 4wd.
Since it is telling you to check the TOD (torque on demand), in my mind is may be related to the control module or the switch itself. I will try to explain. The TOD module determines the selection sent to the transfer case. Now, TOD (aka automatic 4wd or 4hi) on this vehicle is somewhat different. The amount of torque distributed to the front wheels is based on conditions. When the clutch (electronically controlled in the transfer case) is completely disengaged, the rear wheels are driven. When the clutch is completely engaged, a rigid four wheel drive mode is obtained. The torque split status is controlled continuously between the rear wheel and four wheel drive modes. For this to work, many different systems are used.
This system includes front and rear speed sensors, and receives throttle position sensor and engine speed information from the PCM, ABS control unit signal, brake switch signal, and shift motor position information. Any of these can fail, but for it not to shift from 4hi seems like either the switch is bad or the TOD module itself. It is even possible that something has come disconnected.
Honestly, I'm not trying to make it confusing. I just want you to understand my deduction. That leads me to a question. Is there any way you could have the computer scanned for codes related to this system? That would be helpful and at least point us in the right direction. Otherwise, it becomes somewhat of a guessing game. There is even a front axle switch that could be bad preventing the unit from disengaging.
Let me know about the code issue. Also, I have pages of diagnostic flow charts related to the TOD system. If you feel confident to try them, I will be happy to provide the to you.
Let me know
Joe
Monday, September 23rd, 2019 AT 7:15 PM
