i have a battery drain problem,i have done testing ,i have 0.40 m/a, but around 2.97 when i put the fans/acct fuse back in ,i dont understand why this fuse is live with out the ignition on .i have un pluged fans,temp sensors egr and purge sensors and no change cuold it be 02 heaters,if so why are they live ,the battery is dead over night if i leave this fuse in ,car is running fine no codes and 02 are reading correct on data master,thanks scott

 

Always difficult to answer when there is no info at all on the car - year, model, engine, etc. I guess since you mentioned DataMaster, its an OBD-I LT1.

But, in general, the O2 sensors are on a switch power source, meaning when the ignition is switched off, their power source is "off".

Exactly:
-year of vehicle
-engine
-specific fuse you have traced the problem to

 

o.k 94 z28 lt1 , fuse is under hood and fans/actr fuse 6 10 amp,this is live with ignition off,the chilton manual shows its a brown wire hot in run, goes to 02,egr, and canister purge thanks

 

I looked at the 94 "P" diagram in Chiltons, and it shows "HOT IN RUN" = switched with ignition. Shoebox's wiring diagrams also show that circuit as "to ignition". If the fuse it hot with the ignition switch off, you've found your problem.

Shoebox had 95 diagrams, but this circuit is the same 94-95.

http://shbox.com/1/1995_pcm2.jpg

Add a "Signature".

 

ok so any idea what could cause this to be live all the time ,ive had a new pcm recently,so i swapped it to old one ,and still live and still live with no pcm fitted, i thought hot in run was live all the time,thanks for that.i think i will trace the feed to the fuse and see how its getting power,scott

 

fixed it,thanks for the ignihtion clue,i had the wires apart before the new pcm and i put the pink wire into a always live,so i have put it back into the correct connector,ithink you could only do this as the plastic surround on the pink is missing,almost no amps when key off,thanks again,scott