hi i have a 1998 t100 4x4 sr5 i have had some electrical gremlins. about 3 months ago my fuel pump quit while i was driving. then it restarted. i made it home and thought the fuel pume was bad so i replaced it. however i found htat im not getting my ground to one of the pins on the fuel pump relay near the passenger kick pannel. I also found that i have 2 dead fuses on my fuse panel by the drivers kick panel. The dead fuses are the top two on the left looking at the fuse box. Here is my problem. I know that it is related. i was able to jmp the fuel cut off relay and get the truck running but i cant figure out where the open is. The two fuses are not blown and i do not have voltage on either sides of the fuses. so i figure that i have lost my 12 volts to these fues. i have looked all over to try to find the problem but i cant seem to find it.
Can someone tell me what is controlled by these fuses. i know the dome light is one of them, it is not working but has a good light. Im missing my gear selector light on the dash. all other gages seem to work fine.
the truck has 175,000 miles on it and is in good shape. does not go offroad any ideas where the wires may have and open on this vehicles, maybe from rubbing the firewall of other issue..
thanks bill

From my 1998 T-100 2WD extended cab...


Do you have an alarm system? Remote start? If you do, it could be the cause of yer problems. Check the wiring harness and where it hooks up to the alarm setup very carefully. <img src="/forums/images/graemlins/wink.gif" alt="" />

Yes i do have the factory alarm but no remote start. correct me if im wrong but wouldnt the fuses still have voltage even if the alarm is installed. i assume the alarm is installed after the fuse, im not educated on alarm installation. there are some crimp on connectors in that area so ill check them up close. i do remember hearing some relay chattera few months back but was unable to figure out where the sound was from. i knew it was under the dash near my feet but could not isolate the issue. I beleive my alarm seems to work correctly. ill try it and let you know..

My question is which fuse will operate the 4 wheel drive add. i thought it was vacuum actuated and not electric. with the 4 wheel drive. i can hear the gears and syncro's locking in but its not locking the hubs. i cant figure out if is a mechanical problem, electrical or boty...


thanks bill

Thanks fer the info...helps others/me to help you. <img src="/forums/images/graemlins/smile.gif" alt="" />

Yes...there are vacuum switched valves (VSVs) that control the 4WD system. Did you check those as well? I believe there are 2 of them located near the front differential.

Do you have the auto or manual trans? <img src="/forums/images/graemlins/wink.gif" alt="" />

The fuse(s) that send power to the 4WD control system is/are the 10A Gauge (auto/man trans) and 15A Cig (auto trans). This power goes through the integration relay.

How good are yer battery connections? How about yer grounds? The body ground near the battery would be suspect. Shoot some photos and post them up, please. <img src="/forums/images/graemlins/wink.gif" alt="" />

When you checked fer 12V at the fuses, did you check with a body ground and then a battery ground? <img src="/forums/images/graemlins/wink.gif" alt="" />

The left kick panel grounds would be suspect as well. They are located kinda high...almost near the dash support bar.


Hopefully the clicking yer hearing wouldn't be the integration relay as that is the main relay that sends power out from the fuses. Was the vehicle flooded before?

Power distribution from the battery goes to the engine bay fuse box and then to the rest of the vehicle. Power to the ECU-B fuse comes from the 100A Alt fuse via a yellow wire and into an electrical junction (E12) before splitting out to the fuse. The E12 junction also splits out power to the Taillight relay and the subsequent fuses 15A Stop and 15A Tail.

well time work on this again as i will need my 4 wheel drive this winter.
I figured out my bigest electrical problem. or at least i think i did, it seems that the ground strap that connects the firewall to the back of the pass side head was melted. i put a new plug on and now i dont have a fuel pump issue and i think all my fuses work properly. however i still cannot lock into 4wd. i have a 3.4 with auto transmission. the 4wd shifter seems to work properly but it wont go into 4wd. i get no light on the dash to let me know im in 4wd. I pulled off each vacuume line off the VSV. i have vacuume on the lines while the engine is running. so im guessing that they are ok.
i have voltage on the 2 fuses you mentione above.

i have not seen any other ground issues. all connections look good and not corroded. grounds in the kick panel look good also. i only checked the body ground when checking the fuses.

My truck was never flooded but it was putchaced by me as a salvage vehicel back in 2003 and ive never had any problems except 2 bad coils and broken timming belt andreplaced a radiator.

my tail light issue was a cut wire where it pushes up thru the bed near the taillight.
little by little im getting things together however the 4wd is a major "I gotta Have working" i get stuck on wet grass in my backyard on a 25degree slope. I get better traction in my suzuki swift gti then my t100.

Need help with getting started....

thanks bill

Jack up the truck and put it in 4wd and see if all the wheels spin.

The light might just not work.

well no need to jack it up it is deffinately not going into 4wd. i messed with the vacuum lines, I disconnected them from the front actuator one at a time and tried to pull vaccum on them the one that is wrapped (towards the pass side) will not hold a vacuum. i can hear what sounds like air coming from up near the fender. however i am working alone and cannot verify where the problem is. but after i put the hoses back on i had my 4wd dash light come on. When i take out fo 4wd and put i back in 4wd it will not engage. then if i remove the vacuum line and put it back on a few times then it will go back into 4wd.
Im thinking that one of the solenoids on the fender is bad or i have a bad vacuum line. i will check it tonight and post my findings. I did visually inspect the lines but nothing stood out as suspect..

well checked all the vacuum lines and they are good. no breaks or leaks. however when looking at the solenoids on the drivers inner fender i think the one towards the front is not working properly. they both test good with an ohm meeter at 47 ohms so maybe im not getting my voltage to that solenoid. however if i switch the vacuum lines going to the ADD then 4wd works fine, but i suspect that the other solenoid is still not working properly. i do not have a wireing diagram right not so im wondering if someone can tell me where the signal comes from to activate this front solenoid. When i unplug the rear solenoid and connect it back up, i can hear a click when it activates, but not the front solenoid.

thanks bill