Mitsubishi Repair Problems? Ask a Mechanic for Answers ASAP
Are you referring to the Orange C/D Lock light in the center of the four tire lights on the dash?
Hi,When this light comes on and you are not switching between 4WD modes it is indicating a malfunction occurred in the 4WD system. The C/D light doubles as a "check engine" light of sorts for the transfer case ecu.
With the problem occurring while driving at highway speeds, this makes it very likely to be either a vacuum leak or the vacuum solenoid pack (free wheel clutch solenoids) on the passenger frame rail beneath the air filter. That part in particular is incredible common to fail.What happens at high way speed is that you are doing high speed/low throttle conditions (Cruising) which builds a lot of engine vacuum, and if there is a malfunction in the vacuum system this causes the front axle to slightly shift the fork (which is vacuum controlled). When this happens it sends mixed signals to the transfer ecu, as the transfer range lever is reading in one position but the axle detection switch is reading a different position.Obviously the ideal scenario here would be to get it to a shop with a full function scan tool that can read the trouble code setting the C/D light on. In the absence of that luxury though I would be checking thoroughly for any vacuum leaks... hoses that have fallen off or rotted etc. This includes on the engine of course, but also those around the solenoid pack on the frame rail and down on the axle as well. If all look well then the solenoid pack could be bench tested.... both solenoids should read about 35 ohms resistance and they should each pass vacuum/block vacuum (entirely) as voltage is applied/removed. If either won't pass vacuum or leaks vacuum even slightly when the voltage is applied/removed accordingly, then the pack requires replacement.Again that is far and away the most common failure on these, I change them about once a month for people... it is the primary issue we see with the 4WD system on the Montero. Having the system scanned to see what exact faults are set would be the ideal scenario however.