If you are fairly mechanical, you could do it yourself. If it is the
Vacuum solenoid (for the TOD) I think it was $150 or so from St Charles
Isuzu... And if it is the TOD position sensor, I think that was $120 or
so from St. Charles Isuzu as well.
Go to http://www.itog.com
Follow the links to marketplace and you will see St. Charles Isuzu on
there. You can call them up and their prices were wholesale (they were
cheaper than the two dealers by me in Wisconsin) and I think they even
ship for free.
Don't know how much any of these would be if you had a dealer replace
them...The dealer says the solenoid pack is a common fail item (due to the
poor sheild and mount design by Isuzu) I would have thought they would
have a recall on this by now!!!