I bought this 2002 Camaro V6 last year. after 1 day of driving the light came on, PO420 code. Car runs good and gets the mileage it should so been no big deal to me. I decided to repair the problem now, Code checked at autozone said O2 driver side, I did the voltmeter test and the sensor tested as working, I decided to check all the O2's but there is no O2 in front of the Cat. car has only 3 O2's. Looks like the cat has been replaced before. there is a O2 behind the cat, can I get this problem corrected without a Pre cat O2? also I cant find a cable or wiring for the missing O2, so I figure whoever did the install of the new cat must have cut the wires.

 

The O2 sensor behind the cat is the post-cat. The other two are the pre-cat sensors. "In front of the cat" means anywhere ahead of it, but not necessarily directly in front of it.

 

I understand that the car should have a total of (4) O2 sensors. mine has (3). one in each manifold and it has one after the Cat. my manual shows one before the Cat in the exhaust pipe where the Y comes into one pipe. it appears when the cat was replaced the Pre O2 was cut out. Does the car supposed to have 3 or 4 sensors? Can I get the code to clear if I have only 3 sensors on the car.

 

my 97 LT1 has 4 o2 sensors one in each exhaust manifold, one in the y pipe that goes from the drivers side, and the fourth on is kind of hidden a little bit. theres an exhaust hanger on the Y pipe its right behind the bracket on the Y pipe. also the cross member covers it too.

 

The 3.8L engine only has 3 sensors. There is a "Y" pipe that goes into one cat and since it is only one cat there is only one downstream O2 sensor. This is perfectly normal and this is the factory set up. The LT1 and LS1 engines all have 4 O2 sensors as they have 2 cats.

Massey

 

OK what years 3800 have three and what years have 4. My 96 has 4. The headers I bought for my 3800 are setup for 4. If I remember right they said they fit 96-02. I am pretty sure we have talked about this in the past. There is a cutoff year for the 4 sensors. I could go through all the manuals but I am going to bed instead


Note the O2 hole forward of the Cat.

 

'02 3.8L has 3 O2 sensors, I own an '02 RS...

 

Thanks everyone for replying. Makes Sense that a V6 with one Cat would have only 3 sensors. Maybe I can get it fixed.

 

I can say for sure the 3.8L engine had a major update in 99. GM added a TBW setup which removed the cable driven throttle body in favor of a servo based unit. This also had the IAC and Cruise control modules removed, and the TPS became a non replaceable component of the servo assembly. The computer also was changed in this year for the new control system. If at any time the O2 sensor configuration could occure I would imagine this would be the best time to change it.

Massey