i have a 96 Bronco XLT 5.0 90,000 miles

the CEL has been on for a while. had my mechanic check it out.
he pulled codes
133 O2 Sensor B1 S1
135 O2 Heater Circut B1 S1
141 O2 Heater Circut B1 S2
155 O2 Heater Circut B2 S1 came up twice.

so instead of replacing all O2 sensors, we thought we may beable to catch just one code insted of the 4 above after clearing it.

left it at his garage yesterday, he cleared it, let it run awhile, and only code 133 comes up first. He replaces that O2 sensor. runs it again to see if it's taken, after awhile the CEL light comes back on. and all 4 of the codes come on again, this time with the new O2 sensor.

this is basically for my to pass emissions. he's suggesting there maybe a computer issue that he feels I shouldn't waste my money on, since I'm going from replacing an $80 part something that maybe a lot more. however in the county I'm in, i have to have it pass emissions.

any idea as to why he's getting the same 4 codes again with the new O2 sensor??

 

your rig runs on 3 o2 sensors. so replaceing one proably wont fix it. but replaceing all 3 should because they each work off each other. did he replace the plugs,wires,cap/rotor and adjust timing to 12*btdc?

 

nope, just that one O2. a mechanic before this guy said the rotor and cap should be replaced, this guy didn't do that.

 

my whole thing is if he replaces all 3, i dish out what $250-$300 and 2 weeks later that damn light comes back on, then what??

if it's just one o2 code coming up, all 3 should be replaced??

 

then you go get the codes again. the CEL is a tell tale sign when something isn't right with either emission/vaccum/etc. try to DIY the sensors it will save you labor cost, if he charges you on that cost. dont expect -- if you fix one thing everything is going to be huncky dory from there on out. look at it "that one day.. you've done everything you can possibly do to the truck"...im starting to scare myself.

 

Must be OBD-II codes cause they make no sense to me. I do know that replacing all three O2 sonsors is a very good idea. If one is bad the computer is trying to adjust the fuel/air mixture to make the BAD one happy and in the process confusing the $&*% out of the other two! So by fixing ONE of them, you may STILL have to problem for the SAME reason - a bad O2 sensor. Only now, the same symptoms are occurring because the computer is trying to compensate for the OTHER bad O2 sensor or sensors.

Hence the reason for the reappearing codes. Many codes are not even generated until the truck is shut down and restarted. So, when the first O2 sensor was replaced, there was no longer a problem with THAT sensor so when the truck was restarted after replacement, the code wasn't generated. However, if there is another bad O2 sensor, the same symptoms could occur generating the SAME codes while the engine was running immediately after the first sensor was replaced. When the truck was shut down AGAIN, the codes were REgenerated because ANOTHER O2 sensor caused the same codes to generate. The second restart after replacement of the sensor would have yielded the codes again.

 

I dont know......but the prices your quoting sound REAL high to me. You should be able to get all three O2's for under $150 install them yourself......then disconnect the battery for 30 min or so(to clear the old codes), and then take it to auto zone (if you dont have a friend of reasonable shop) to check for codes. You NEED to replace all three at the same time, at 90K its over due. Cap, rotor, plugs, wires......when were these done last?

 

i had a tune up in november, but the rotor and cap were suggested to be replaced by another mechanic about 1 month ago.

 

time for some new mechanics. a tune up always consists of at least plugs,cap/rotor and fuel filter change. the wires can go a bit longer then plugs will. what plugs are you running in that rig. If there platinum plugs i suggest you remove them for some motorcraft,autolite copper plugs

 

I would have to assume that your Nov tune up did include the cap, rotor, wires, and plugs.....no? even if half a$$ parts were used they should all still be good.

Replace all three o2's and then clear the codes (you can remove the neg cable from the battery for 30 min should do it) they get the codes checked again. Better yet even with OBD-II you can get a decent reader for like $125 or so......check out some of the sponsors here on FTE.

 

and do this work yourself. its not hard , get a haynes manual if you need to. its amazing how much you can save by doing this stuff yourself. theres at least 75% of stuff on your rig that with a manual any guy with tools can fix or work on with out taking it in.

 

yeah frog, im 17 with a very limited budget and i had very similiar problems. most people i talk to are putting their "thick wires" in for "more horsepower". i have to say bull. but, getting a decent pair of thicker wires is a good idea if they were not just done. also, the spark plug idea from kemical is an awesome recommendation. rotor and cap are neccesary with plugs and wires and will make a world of difference if you can resolve the other issue. unfortunetly, thats not ur problem. i went and bought a haynes manual, and i managed to install a cam, gears, rewire my harness after a fire, and replace every vacuum line on my 90 bronco. trust me on this, make sure you have the tools before you go ahead and rip it out of disect it wondering wut this thingymabobber does. i learned the hard way. that code system sucks but it can be done. fordfuelinjection.com- it was my bible for 2 months, check it out!