4 Wheel Drive/SUVs: Diff Warning Light on dashboard, differential switch, mitsubishi shogun

Question
QUESTION: Hi, I am from England and I have a Mitsubishi Shogun 2002. 3.2 Diesel.My problem is if I drive in a straight line(on the Highway)for approx 15-17 miles the diff lock light starts flashing on the dashboard.The handbook tells me not to drive the vehicle.Local garages have had 6 attempts to fix the problem so far but the light still flashes when I drive the distance explained.  The strange thing is that if I do 15-17 miles around town it does not happen only when I do a straight line. Please have you any ideas.
Many Thanks
Molly

ANSWER: you may test the differential switch to see if it maybe bad and also check the ground.

This may not fix your problem but it is a start.

---------- FOLLOW-UP ----------

QUESTION: I have had the differential switch changed and the ground is a main road which is tarmacked.

Answer
I meant check the ground as ground wire, there is also a switch that has vacuum running to it on the transfer case check that and make sure there is vacuum going to it. Sounds as if the switch itself could be shorted also.


It honestly seems that more than likely you have a short in that system after reviewing my notes on some of the work I have done on these.

Wiring is a very intense thing to do on a vehicle and it takes some one who has patients to do wiring.

Thanks