: o2 sensors!!!!!! argggggggg



cadillac6
11-30-03, 08:50 PM
Ok as you all know I have been posting because I have been having problems with o2 sensors in my 97 caddy concours. I first I replaced 2. "service engine light" went off. Then came back on reading to me that it was a o2 "heater sensor" bought 2 more. "service engine light" went off. So now I have 4 brand new o2 sensors in my car. I just got home and the LIGHT came BACK on!! saying its the heater sensors in the o2's? come on now! could this be some sort of glitch???? pleeeaaaasssseeee help me guys before it is too late so i can sell this thing!

DaveSmed
11-30-03, 08:53 PM
When you swapped them out, did any of the connectors look "well done"? Sometimes they get cooked and then become open, or short to ground.

cadillac6
12-01-03, 12:40 AM
When you swapped them out, did any of the connectors look "well done"? Sometimes they get cooked and then become open, or short to ground.


Well in one of the codes it read "insufficient switching"? whatever that mean I just dont know what to do with this crap

mcowden
12-01-03, 01:04 PM
Well in one of the codes it read "insufficient switching"? whatever that mean I just dont know what to do with this crap
Hi cadillac6 -

I replaced 4 O2 sensors on my '96 SLS about 30,000 miles ago (at a total cost of about $320) and learned a few things that might be helpful:

The two sensors in the engine compartment that are in the manifold on either side of the engine are unheated sensors. Being that close to the engine, I assume they heat up fast enough that heaters aren't required. The two sensors under the car, before and after the catalytic converter, are heated. Both types of sensors have 4 wires.

Besides the heated/unheated difference, the wiring harness is a little different so you don't accidentally put the wrong kind in there somewhere. This can be a problem if you use the "generic" O2 sensors that require you to cut the harness off the original sensor and splice it onto the new sensor. The connectors I've seen with the generic sensors are not the greatest things in the world and you have to be careful to make a good connection on all 4 wires and not pinch them when putting on that weatherproof casing.

Also, the wiring for the two heated sensors gets routed above a protective sheet metal shield that has plenty of sharp edges and opportunities to cut wires. Be sure there are no cut wires and that all the connectors are nice and tight. I know this may seem silly, but it's important because the signal from an O2 sensor is only about 1 volt and very low current. What may seem like a minor wire pinch or imperfection can be devastating to a 1 volt signal at very low current. Splicing O2 sensor wires is really not a good idea, in my opinion, because it introduces unknowns that weren't there before.

After the sensors are replaced, you might have to clear out PCM codes to eliminate the warnings on the dash. If, after checking these items there is still a problem, it could be a batch of bad gas or some injector cleaner additives have done that to me before.

If it was me, I would take a quick look at the wiring for the sensors under the car to make sure the wiring and connectors are 100%, clear out the codes, and drive it for a while longer to allow time for the PCM to re-adjust the mix for the new O2 sensor readings. It may very well go away after some driving or a fresh tank of premium unleaded.

If it's still a problem, or this just doesn't seem feasible to you, a mechanic may be able to check the sensors to make sure they're working right and there isn't a short inside the sensor body. I have heard of new sensors testing bad.

Are there any other factors here, like is it running OK otherwise? How is the gas mileage? Besides the O2 sensor codes, are there any other codes? How many miles are on the car? What other maintenance has been done? Does the exhaust smell like rotten eggs (sulphur) or does it still have a distinct gas smell after driving several miles? Is the exhaust smoky on a warm day at full running temperature? Is it burning an excessive amount of oil? Have you looked or listened for vacuum leaks?

Just a few thoughts. Hopefully that will help get you back in good shape again.

cadillac6
12-02-03, 08:56 PM
Hi cadillac6 -

I replaced 4 O2 sensors on my '96 SLS about 30,000 miles ago (at a total cost of about $320) and learned a few things that might be helpful:

The two sensors in the engine compartment that are in the manifold on either side of the engine are unheated sensors. Being that close to the engine, I assume they heat up fast enough that heaters aren't required. The two sensors under the car, before and after the catalytic converter, are heated. Both types of sensors have 4 wires.

Besides the heated/unheated difference, the wiring harness is a little different so you don't accidentally put the wrong kind in there somewhere. This can be a problem if you use the "generic" O2 sensors that require you to cut the harness off the original sensor and splice it onto the new sensor. The connectors I've seen with the generic sensors are not the greatest things in the world and you have to be careful to make a good connection on all 4 wires and not pinch them when putting on that weatherproof casing.

Also, the wiring for the two heated sensors gets routed above a protective sheet metal shield that has plenty of sharp edges and opportunities to cut wires. Be sure there are no cut wires and that all the connectors are nice and tight. I know this may seem silly, but it's important because the signal from an O2 sensor is only about 1 volt and very low current. What may seem like a minor wire pinch or imperfection can be devastating to a 1 volt signal at very low current. Splicing O2 sensor wires is really not a good idea, in my opinion, because it introduces unknowns that weren't there before.

After the sensors are replaced, you might have to clear out PCM codes to eliminate the warnings on the dash. If, after checking these items there is still a problem, it could be a batch of bad gas or some injector cleaner additives have done that to me before.

If it was me, I would take a quick look at the wiring for the sensors under the car to make sure the wiring and connectors are 100%, clear out the codes, and drive it for a while longer to allow time for the PCM to re-adjust the mix for the new O2 sensor readings. It may very well go away after some driving or a fresh tank of premium unleaded.

If it's still a problem, or this just doesn't seem feasible to you, a mechanic may be able to check the sensors to make sure they're working right and there isn't a short inside the sensor body. I have heard of new sensors testing bad.

Are there any other factors here, like is it running OK otherwise? How is the gas mileage? Besides the O2 sensor codes, are there any other codes? How many miles are on the car? What other maintenance has been done? Does the exhaust smell like rotten eggs (sulphur) or does it still have a distinct gas smell after driving several miles? Is the exhaust smoky on a warm day at full running temperature? Is it burning an excessive amount of oil? Have you looked or listened for vacuum leaks?

Just a few thoughts. Hopefully that will help get you back in good shape again.
there are other codes yes but they are minor those o2 heater sensor codes are the only ones that make my "service engine light" come on. there is 80,500 miles on the car. I dont know what other maintenence has been done because i just bought the car 3000 miles ago. It ran fine when I first bought it but now...I feel a little something in the pedal I havnt felt before. Not smooth though. The exhaust doesnt smell like sulfur. Not really smoky on a warm day. It was burning oil bad 2 weeks ago but ive been checking every day and hasnt since. And I dont know how to look or listen for vaccum leaks. My last stand? im taking it to the caddy dealer here in town. Im dreading that because if its not under warranty it means $$$$ but if it will solve this problem I dont care at this point.