Toyota Repair: T100 4wd& check engine light, obd ii, vacuum hose

Question
I have a 1995 at 3.4 with a 5 speed manual transmission with 70k miles. When I engage the 4wd shifter handle I hear a relay engage but truck does not always go into 4wd. Then sometimes next day I will come out and truck will be in 4wd and 4wd light on. Dealer has looked at several times and found nothing wrong. Problem seems to be more prevelant when it is damp. Now it wont go into 4wd at all Living in snow country when I need 4wd I need it. My check engine light refuses to go out after doing tuneup How can I check what the code is that is causing light to come on? Thanks Jeff

Answer
The 3.4L 5vz-fe is OBD-II compliant. Connect it to a scanner while the check engine light is on. If you don't have one, drive to Autozone. They'll ask you if it's a 1996, or later. Just lie to them so they don't hassle you.



What *normally* happens in a case like yours is that there is a vacuum hose that runs down by the differential. It can be cracked, or damaged. When it is, the 4wd light will come on indicating that the 4wd actuator has been engaged, but the differential will not engaged because it has no vacuum assist.
Another trick is to drive in reverse & try to engaged 4wd.

Be careful not to use any 4wd vehicle when you don't need to on the road.