Cat converter sensors question

[Jusjazz]

Can anyone enlighten me for vehicles with 2 sensors on th cat area( before n after ), is it a must to remove the sensor after the cat converter? Thanks in advance!

[Jusjazz]

I mean actually after I de-cat the converter...

[Yeobh]

It's getting more difficult to fool the on-board computer especially with the lean burn monitoring lambda.

[Jusjazz]

So u mean after de-cat and take out the after sensor will create mulfunction on the onboard computer?

[Normal_aspirated]

engine-check light will come on......

[Yeobh]

The lambda sensors are designed solely to monitor the product of the exhaust. The measuring time is in nano second and switch from 0-5volt.Once the on-computer do not receive any voltage from the sensor it will assume the exhaust is lean and the on-board computer will increase the fuel injection time. Yr ride will continue to run on very rich mixture causing eviromental pollution and keeping the TP busy.

If your rid is an european or high end Japanese car, the on-board computer sesnsing the emission checking and monitoring system is fualty will flag the engine check light on. It will continue to monitor the fault and gradual shift the driving mode programme downwards - affecting yr max vehicle speed Once it reaches the final limp mode, the car will be shute down for good.

[BlueSi]

OBDI cars only have one O2 sensor, the primary O2 sensor which is upstream of the CAT.

 

OBDII cars come with two O2 sensors, the primary O2 sensor at the same place, and the secondary O2 sensor on the CAT itself. Only the prinary sensor is a feedback sensor, meaning if its damaged, it'll affect the way ur motor runs. The secondary sensor is just there for monitoring purpose.

 

If either of the sensor is faulty, it'll throw a CEL (check engine light). The only way to know which sensor is faulty is to diagnose and find out what code is being thrown and which sensor that code refers to. The dealer and some shops will have a hand held unit that plugs into ur ECU to check a code. In some cars, there are tricks to jump certain connectors and check for the code yourself.

 

Do not remove the orimary sensor. The secondary sensor is optional if you can live with the CEL. There are products out there that will trick the ECU making it think there's a secondary sensor when there actuallt isn't one, but this is done only when toy wanna remove your CAT and replace it with a straight pipe. The other option will be to change your ECU to an OBDI ECU. That will not throw a CEL in the abscence of the secondary O2 sensor.

 

Hope this helps.

 

[Dwoon]

Is it O2 or EGT sensor?

 

I thought that there's only one O2 sensor upstream of the CAT, the rest down stream are EGT sensors which are used to monitor the CATs and to prevent damage to them?

[BlueSi]

I'm pretty sure they'er O2 sensors, not sure if stock cars come with EGT sensors at all, EGT's are not cheap.

 

The secondary sensor doesn't do anything really, just reference readings with set maps stored in the ECU. If anything's not right, they throw a CEL.

 

[Noregretforever]