Catalytic converter install issue

[russiankid]

Not all cars have an after cat sensor.

[240sxDann]

Right, all fuel injected cars have an upstream, but only some OBD1, and all OBDII cars have downstreams.

[Erik]

Originally Posted by russiankid

Not all cars have an after cat sensor.

i know my car does, its about 2 feet following the catalytic converter

[Erik]

the vibration sounds like its from the front of the car, although the scanner read a rear cat was bad and that was it. could it be the exhaust manifold possibly?

[240sxDann]

open the hood and rev it up at the throttle body and listen for it. Could be a ton of things.

[pinacup7]

Originally Posted by 240sxDann

O2 sensors read in voltage up to .05 I believe. The voltage is determined by how much of certain exhaust properties that their are (i.e. carbon monoxide etc). If there is too much of said exhaust properties, the voltage goes higher, which then tells the ecu "ok theres something wrong here, I shouldn't be seeing this much voltage, the cat is bad" and it throws a light. If you put a resistor in line with the right resistance, even if you have no cat, it will keep the voltage within its parameters and the ECU will not think anything is wrong, therefore no CEL.

This is mostly right. But o2 sensors only read oxygen.

Originally Posted by 240sxDann

As far as I know, down stream O2 sensors are only to indicate whether or not the cat(s) are working properly. Upstream are for fuel control. But somebody correct me if I'm wrong.

That is correct

[240sxDann]

yea I guess that would make sense....hence...."oxygen" sensor. LOL!