Switching to 4WD without Permission?

[kodachrome9319]

Last night when driving home on I-40 from Flagstaff, I was in 2HI at 83MPH, cruise control and I felt this little kick. I look down and its automatically put its self in Auto 4WD and was starting to flash for 4-LO. I quickly turned it to AUTO and back to 2HI then pulled over, turned the engine off, and turned it back on. No problems after that for the rest of the drive home (200 miles).

Just wondering if anyones had this issue, or knows what's up?

Thanks!

[Trail X]

The 4WD switch works based upon resistance.

Based upon your switch setting, the circuit registers different resistance levels based on the below chart:

2HI: 240 Ohms
Auto: 560 Ohms
4HI: 1.1k Ohms
4LO: 2.2k Ohms
Neutral: 5.1k Ohms

The resistance levels go up as you go down the chart.

So when the contact gets slightly corroded within the switch, it will jump the resistance to a higher level. It sounds like you had a bad connection with your internal switch contacts, and you were getting a higher resistance value return to the TCCM.

For this reason, it's a good idea to "excersize" your switch once in a while. This means cycling your switch a few times back and forth while the car is off, just to ensure the contacts remain clean and corrosion free. If you continue experiencing this issue, it might be time to replace your switch.

[kodachrome9319]

For this reason, it's a good idea to "excersize" your switch once in a while. This means cycling your switch a few times back and forth while the car is off, just to ensure the contacts remain clean and corrosion free. If you continue experiencing this issue, it might be time to replace your switch.

Hmm, I've been frequently using all the "functions", used all 4 the day that the problems happened... We recently got 8" of snow, too, so 4WD has been utilized a lot lately. I don't think the switch has became lazy, but, never know.

[Trail X]

Alright, I wasn't sure what your specific situation was. It sounds like your contacts get exercised often, so it may not be corrosion... it may just simply be a bad switch. If it's not a bad switch, there are only two other components it could be: the TCCM, or the wiring itself.