I have had some water leaking onto GEM module and fuse box. Also had the #21 fuse blow when I tried to start truck. Replaced both the GEM and the Fuse box and fixed the radio and fan blower staying on problem. But even with new parts, the #21 fuse still pops instantly when I try to start the truck.

Can this be a Starter/Solenoid issue or another under dash wiring problem?
Any help would be greatly appreciated

 

You are talking about CJB ( aka Central Junction Box / Cab fuse panel ) fuse #21 ?

If so, the GEM has nothing to do with this. This fuse is hot in the Start position via the ign switch and is to the DTR ( Digital Transmission Range ) sensor on the side of the trans, then to the start motor relay on the firewall.

My paper copy has a different diagram than the DVD diagram, so I am not sure which to believe.

The 2001 & 2002 owners manual list fuse #21 as powering Fuse # 20 which has the GEM as one of the items.

Is fuse #20 the factory size ?

 

Yeah I believe fuse #20 to be factory size. I just put a new CJB in from the dealership that was fully loaded with fuses and relay's. The GEM had given me problems before when it rained the water would leak in and cause my radio to come on and run down the battery. It dried itself out and worked fine. This time I came out to a dead battery, charged it and when I tried to start it the #21 15a fuse blew instantly. No attempt to turn over. All other power worked fine, other than the radio staying on when I took the keys out.

I talked to the dealership, replaced the GEM and Fuse box or CJB and hoped all would be fixed. Radio no longer stays on, but I have no radio display lights and the new fuse #21 still blows instantly with no effort to turn over.

The two modules that plug into the back of the CJB under the GEM show signs of water also, but appear to be all hard wired. Could one of these be the source of the problem? Or hopefully there is something else.

 

Update:

I went and picked up a multimeter, although I have no idea how to use it. I'm hoping someone here could give me a quick once over on what to do with it to find a short.

Hopefully this will help narrow it down as to what I'm looking for. I unplugged the DTR Sensor from the transmission. When I try to start now, the fuse no longer blows. Does anyone know where the problem might lie with this new info?

I inspected the wire looms that run back around the manifold on the passenger side of the truck, as far as I can tell everything looks fine. Everything is still encased in the loom with no signs of melting or burning threw.

My thinking is, it would be something that could have gotten wet up under the dash when the fuse box and GEM got ruined. Could the ignition switch itself be bad or does it almost have to be the wire going to the DTR sensor?

Any help is appreciated... I am lost right now.