rear oxygen sensor on 1999 Saturn SL2

I brought my car to the shop for a possible faulty rear oxygen sensor and was quoted $969 to fix it. They said that when replacing the rear oxygen sensor there's a 50/50 chance that the threads on the catalytic converter would get messed up causing it to have to be replaced also. There is nothing actually wrong with the catalytic converter right now though. This sounds strange to me. Is it actually possible to ruin the cat by just replacing the O2 sensor or is the shop trying to screw me over?

by in Saint Paul, MN on May 26, 2011
5 answers 2 comments
ANSWER by on May 26, 2011
Best thing to do is get another opinion from a different shop and you can locate a shop near you here
ANSWER by on May 26, 2011
O2 sensors can seize and damage threads but can often be repaired with the proper tap. Often a rear O2 code is set due to a nonworking cat convertor, but it could also be a failed sensor. A little more diagnosis is needed here before jumping to any conclusions.
COMMENT by on May 26, 2011
the shop actually said it was the O2 sensor so I wasn't jumping to conclusions rather just questioning why a properly working catalytic converter(also their diagnosis) would need replacing since that sounded strange.
COMMENT by on May 27, 2011
Thats why I recommend to get another opinion
ANSWER by on May 30, 2011
A cold oxygen sensor is extreamly tight in the threaded area and can tear threads when being removed. Sometimes minimal damage. To avoid any kind of damage it is best to apply a shot of Liquid Wrench, WD-40 or similar lubricants while the sensor thread area is cold (or cool) then start the vehicle and allow the sensor to get hot and while avoiding a burn to the hands you can turn the sensor out without any trouble. This has worked many times for me. HEAT HELPS
ANSWER by on January 04, 2013
hi they definelly trying to screw you, for those having this problem with oxygen sensor,first check under of dash driver side and or under of the hood for a fuse box,there is a fuse with letter htr or fi htr its probably blow if so switch it hope helps thanks
ANSWER by on November 03, 2015
Yes and NO Honestly get the exhost hot apply some WD-40 or prefered lube and give it a go. I have done sensor changes cold and warm with lubricant makes it much mor easy I have never had threads strip when changing sensors but have friends that have managed to do such so honestly I think you could find a bit better price though.

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