I have a 98 5 speed and just recently all the gauges quit working. speedo, tach, temp, volts, fuel, oil, and wts all not working and the odom just flashes. i ran the test by pushing the trip button and got codes 920, 921, 999. I hooked it up to the obd II and it will not link up.
I have read previous threads about problems like this but i know nothing about the electrical part. What is the PCM and ECM and were are they located? any help would be greatly appriciated and if anyone would like to take the time to explain how all these components work together and what exactly they do that would be greatly appriciated as well.

 

rite b4 i got my truck the gauges werent working and turned out to be a fuse some where, i think the guy said it was and inline under the dash or somthing, but a 98 might be diff,

 

Check all wiring harness grounds on the engine.

 

On my '94, only the Tach, Alternator, Speedometer, AC, and dummy lights, not including the ABS light (ABS works off an independent computer), were dead. Also, those diagnostic tool things wouldn't connect to my truck's computer. The fuel gauge, temp gauge and oil gauge still worked, though.

Ended up buying a salvaged computer, and it fixed it.

My dad put it on and it was his connection that he bought it from (cost about 170 bucks or something...my dad knows a lot of people and always tends to get discounts like that), so I don't know where the computer is located on the truck. But, I think on the '94 it's in front of the firewall on the passenger side just behind the air filter, box....

At least, I think it's that black box looking thing, because the device, there, has chalk written numbers on it that gives me a salvage yard look, to it. I'd have to ask him, to be sure, though....

Heh, My dad hate's my truck.... That was the third time he had to work on it. First time the lift pump went out on it, Second time the driver side door hinge broke and had to replace it, then that computer... all, within the same year... So neatless to say, he wants nothing more to do with it; which is why I still have the 4K-GSK kit sitting in it's postal box.

 

check the block fuses in the fuse box in the engin compartment mine did that and it was one of the green fuses that was blown