Hi guys! new to caddy and forum need some help

[97pearl]

I just got a killer deal on a 1997 deville. its a beauty and has 135 thousand only thing wrong is it is showing up four bad o2 sensors. what would make it show 4 bad o2s at once? i have cleared the codes they go away but come back in less than a mile. please don't tell me hg lol.

[Texas Jim]

Are all four o2 sensors showing lean codes?

If so...I would suspect a bad vacuum leak.

[Bruce Nunnally]

O2 sensors are maintenance items. The o2 sensor manufacturers say to replace them every 50k miles or so. If all 4 suddenly went at once I would suspect something is killing them. However, if you just got the car and are diagnosing it, you will have to start with 4 known good sensors and work from there I would think.

[BodybyFisher]

Do you have any driveability issues? Do you smell fuel? A leaky injector(s) or fuel pressure regulator should be considered. I learned something below, I DID NOT know that silicone sealer used ANYWHERE can cause problems with an O2 sensor, I thought it's O2 sensor killing use was limited only to fuel system useage.

Home or professional auto repairs that have used silicone gasket sealer that is not specifically labeled "Oxygen sensor safe", "Sensor safe", or something similar, if used in an area that is connected to the crankcase. This includes valve covers, oil pan, or nearly any other gasket or seal that controls engine oil. Leaded fuel will ruin the O2 sensor in a short time. If a car is running rich over a long period, the sensor may become plugged up or even destroyed. Just shorting out the sensor output wire will not usually hurt the sensor. This simply grounds the output voltage to zero. Once the wiring is repaired, the circuit operates normally. Undercoating, antifreeze or oil on the *outside* surface of the sensor can kill it.

Reference > http://www.mr2.com/TEXT/O2_Sensor.html

You need to specifically give us the DTC codes you are getting.

Please read your ON BOARD diagnotics by doing this

go to www.caddyinfo.com

go to HOW TO

go to DTC CODES

find out how to read codes for your year and follow the directions

Post the codes that come up on your dash here and we can help you

We are unable to help because we do not know what kind of codes you are getting

Welcome aboard

[97pearl]

thanks guys i will have to get the guys at autozone to read the codes for me again and ill write them down. he scanned them an said "you have 12 codes but they are all the same thing... you have 4 bad o2 sensors". no the car drives perfectly no misses it idles great has TONS of power have only driven about 500 miles but no problems the coolant will go up to around 225 when your sitting in a drive thru for a long time but goes right back down to 196 or so when you start to move. no leaks no smells it gets 25mpg the only way even knew there was a problem was the light is on. somone had said maybe a head gasket because the N* is plagued with them and the coolant fouled the sensors but no white vapor no coolant in the oil and no leaks or smells or oil in the coolant.

[BodybyFisher]

thanks guys i will have to get the guys at autozone to read the codes for me again and ill write them down. he scanned them an said "you have 12 codes but they are all the same thing... you have 4 bad o2 sensors". no the car drives perfectly no misses it idles great has TONS of power have only driven about 500 miles but no problems the coolant will go up to around 225 when your sitting in a drive thru for a long time but goes right back down to 196 or so when you start to move. no leaks no smells it gets 25mpg the only way even knew there was a problem was the light is on. somone had said maybe a head gasket because the N* is plagued with them and the coolant fouled the sensors but no white vapor no coolant in the oil and no leaks or smells or oil in the coolant.

1) you DO NOT need to go to Autozone to have them read the codes, you CAN read them yourself, I gave you the way to do it above

2) 225 sitting still is NOT overheating, it is NORMAL, 196 is great when you are moving

3) ignore all the rumors about the NS, can a head gasket go bad, yes, but its not PLAGUED

Please post the codes you have and we can help, again forget AUTOZONE, it is not necessary

[Ranger]

I learned something below, I DID NOT know that silicone sealer used ANYWHERE can cause problems with an O2 sensor, I thought it's O2 sensor killing use was limited only to fuel system useage.

I remember the old Guru telling us that. I believe his words where, Silicone anywhere the intake is "instant death" to an O2 sensor.

[BodybyFisher]

Yes, but I did not know that silicone sealer used on the oiling system (cam covers, pan, etc) could also be a problem for O2 sensors

[Ranger]

Hmm, I don't recall him addressing that. I too would not expect that to be a problem once cured. I guess those little bugger are extremely silicone sensitive.