Catalytic Converter/how do you know
Racer
Joined: Jun 2006
Posts: 408
Likes: 0
From: Elkton MD
Bad Cat
A '96 has OBD II with O2 sensors behind the cats. If the cats don't work, it will set a code and illuminate the service engine light. Computer needs conditions of stable operating temp and load then sets the code and light after the second incident (restart). Must be reset with a code reader, disconnecting the battery won't reset the computer.
Just went through this with my wife's '96 blazer.
Just went through this with my wife's '96 blazer.
Instructor
Joined: Sep 2008
Posts: 152
Likes: 0
From: O'Fallon Missouri
the OBDII code is P0420.
Also if you have acess to a good scanner you can watch the waveforms on the O2 sensors. rears should run slower than the fronts. if they run at the same speed there's kitty problems. you can also check with an o-scope. make sure it can graph 4X or have a really good memory.......
Also if you have that nasty rotten egg smell..... Bad Kitty!
Also if you have acess to a good scanner you can watch the waveforms on the O2 sensors. rears should run slower than the fronts. if they run at the same speed there's kitty problems. you can also check with an o-scope. make sure it can graph 4X or have a really good memory.......
Also if you have that nasty rotten egg smell..... Bad Kitty!
Heel & Toe
Joined: May 2007
Posts: 21
Likes: 0
From: UT
If you are concerned about the emissions readings, you can check the temp with a temperature gun on the inlet and then the outlet. The temperature should be at least 100 degrees hotter behind the CAT. If not, you have a bad CAT.
If you have a running problem like bogging or it seems like your car can't breathe, the back pressure test will tell you if it is plugged. You just need a vacuum gauge and an adapter that screws into the O2 sensor port before the cat. If it is higher than 3 you have a restriction.
If you have a MIL on, then if the code is for the post CAT O2 sensor, you need to watch the difference in readings from the Pre-Cat O2 and the post-Cat O2. The wave form of the front O2 should change regularly from 1.0v - 0.01v. The post-cat O2 should NOT mirror the pre-cat O2, it should be fairly flat.
Hope that helps.
If you have a running problem like bogging or it seems like your car can't breathe, the back pressure test will tell you if it is plugged. You just need a vacuum gauge and an adapter that screws into the O2 sensor port before the cat. If it is higher than 3 you have a restriction.
If you have a MIL on, then if the code is for the post CAT O2 sensor, you need to watch the difference in readings from the Pre-Cat O2 and the post-Cat O2. The wave form of the front O2 should change regularly from 1.0v - 0.01v. The post-cat O2 should NOT mirror the pre-cat O2, it should be fairly flat.
Hope that helps.
Melting Slicks
Joined: Feb 2008
Posts: 3,286
Likes: 6
From: Palm Beach
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Le Mans Master
Joined: Dec 2004
Posts: 5,789
Likes: 8
From: Myrtle Beach SC
St. Jude Donor '05-'06
95 and 96 both have pre and post cat O2s but someone told me the post one did nothing
When in reality it IS checking the operation of the cat. Yours being a 96 and OBD II it should toss a code. I am not sure if you were the guy with the glowing cat are you? Also I am not sure if a plugged or broken cat will toss a code or not obviously the pre and post signal would be different in either case.
Drifting
Joined: Jul 2007
Posts: 1,293
Likes: 36
95 and 96 both have pre and post cat O2s but someone told me the post one did nothing When in reality it IS checking the operation of the cat. Yours being a 96 and OBD II it should toss a code. I am not sure if you were the guy with the glowing cat are you? Also I am not sure if a plugged or broken cat will toss a code or not obviously the pre and post signal would be different in either case.
I have a 96. When the right cat went bad, I heard a rattling sound at idle and then it threw a code saying the CAT was inefficient. A new CAT fixed that.
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA