I started up my truck last night and suddenly it died. I checked the fuses and my 15A EFI fuse was blown. Walked to a gas station and got a new fuse, replaced it, and it blew again. The engine turned but would not pop.

I read on these forums that a common cause of this is the O2 sensor. I unplugged both of them and the truck fired right up.

I am not sure if it was the act of unplugging the sensors or me moving the wiring harness that fixed this problem.

1) Is this usually the O2 sensor shorted out, or the wiring harness shorted out?

2) What do the O2 sensors do other than smog crap? I live in a state that does not do smog checks and if I don't need these O2 sensors, I'll just leave them unplugged. Is this a good/bad idea?

Bad idea to leave unplugged. O2 sensor basically checks o2 quantity in the exhaust sends info to computor. Computor then adjust your mixture. Don't forget O2 sensor is only one factor in the fuel mixture equation. O2 sensors are fairly cheap and take 5 minutes to change. You're going to waste more money on fuel then the O2 sensor is worth plus poor performance.

It's usually the wire...

Look at the wires closely, and see if they melted onto the exhaust. Tape it up, and secure it away from the exhaust system.

You need the o2 sensor. Without it, the computer can't tell how to regulate the fuel mixture, and will run like total crap.

Forgot to add. O2 sensors will flat line not short. Usually the wires will short and usually by touching the exhaust.

I can't find one melted/exposed wire down there... I'll go find some new O2 sensors and see if that fixes it. If not, time to call the auto-electrician.

Rich, for you:

www.sparkplugs.com

and

www.autoshop101.com the emissions tech articles there will help you understand the role the 02 sensor plays.

Few years ago on my '86 I kept poppin' the ENG 15a fuse; had a chaffed wire on the harness down near the starter area.

We have a 93 FSM sticky'd at the top of this section; if you don't find what you need, spend the $10 at www.techinfo.toyota.com for schematics, etc.

Do not try to use bosch sensors, use denso