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o2 sensors? normal specs

2K views 8 replies 4 participants last post by  rev_les 
#1 ·
i did search and i could not find a normal operating average reading on idle for a safari or astro

mine is a 2004 safari awd with 145K miles the cat was never change and i get the efficiency code . i read and noticed many said that need replace cat, but mine looks ok i still get water out of the tailpipe. problem i noticed with a computer scanner is the o2 sensor readings..

the sensors before cat with cold engine start normal from .1 but the one afther cat is always over .600mv is that a bad sensor why showing so high when i barely start engine and the precat o2s are lower.
 
#2 ·
The post cat sensors are reading different than the pre cat sensors because the cat is working properly.

If the post and pre cat sensors were reading exactly the same, it would show the PCM that the cat was missing, and set a code.

As long as it fluctuates anywhere between 50mv and 950mv, things are working as intended. Outside these parameters, and it also sets a code.
 
#3 ·
so what is suppose to be? the o2 starts with .5 and gows up from there? makes no sense since my van gets average before cat .7 that is only .2 difference of course the computer acting up... do you know what normally is? i do not have another car to test.

also my van idles around 600Rpm is that normal? i thought 900 is normal.

would a resistor bleeder drooping the voltage help cheat the test? or a spacer?
 
#4 ·
Hi adibv5

Odd question, but do you have an aftermarket alarm installed? Thanks.:)
 
#6 ·
The reason for me asking this is their is a service bulletin out on how the after market alarms should be hooked up. If the alarm or any other after market item is connected to the PCM power circuit it will throw the computer out of sync and can cause a misfire code and ruin the Cat. Any after market item you plan to install in your vehicle, "must" be hooked up the the starter circuit only. Just a heads up on that.:)
 
#7 ·
amazing how just hooking up a wire to an incorrect place causes a chain reaction.folks don't get the fact that modern car's control systems are extremely sensitive to voltage changes,( or the fact that a lot of these circuits FUNCTION using voltage changes)or are digital. When I worked for Hummer, we had them in all the time with a myriad of problems related to (a type of snake or a Dodge sports car.. you figure the name out) alarm and remote starter systems.Not one of them was ever integrated to the class II databus via the readily available adapter. I saw a Benz a "MECP" certified tech hooked some stuff to with problems in the audio-phone system.. the jackalope had tried putting a crimp on connector on the shiny "orange" wire without ever testing it. ( it's a fiber optic line) lol.sorry for hijacking this, but the moral is....Know what you're tapping into, and throw that test light away and get a DVM. And do NOT let anyone at a fleamarket install electronics on your car!
 
#8 ·
would high voltage have something to do with it? my meter reads about 17-18 volt when car running. i also have 2 batterys

also what you mean starter? all the extra lights i have on the car are connected to a separate fusebox that feeds into battery directly i did not noticed any cuts into the power feed for computer , also i plan on do the same thing with alarmsystem main voltage from battery with fuse in between of course.
 
#9 ·
the starter circuit should heat up during "key to start" only . 17 to 18 volts is high, you should read around 14.5 with the engine running, give or take a couple of tenths. ( 14.3 to 14.7).some people that know these vans more intimately will toss you more specific info, i'm sure!
 
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