Catless CEL Fix

[blh_wakeboard]

^+1 I put mine in about 3 weeks ago and haven't had the CEL return or any other codes, worked perfectly! Gotta get my emissions done next month glad I found this thread in time...

 

[RichB]

I'm interested in seeing if this still passes emissions.

 

[blh_wakeboard]

Well in my state if it's a newer car, all you have to do is plug it up to the computer and as long as there is no check engine code it will pass, if the shop notices there are no cats they will fail you unless you got buddies there So getting that CEL to go away pretty much means I'm good to go... I also only have to do S&E every 2 years for the first 8 years of the vehicles life. Did you notice that your A/F leaned out just ever so slightly after putting the diode in?

 

[RichB]

I still have a cat so I should be good then. I haven't looked and my AFRs since putting the diode in but I was pig rich before so if it leaned it out, I'm fine with it.

 

[Wurf]

I really hate to awaken such an old thread but can anyone explain why using a diode to create a voltage drop works better than a resistor in this situation?

I diode simply blocks current flow in one direction. A resistor simply adds resistance to current flow, drops voltage depending on ohm rating, and doesn't care which way you hook it up.

 

[RichB]

Yea, but for some reason the diode works and the resistors don't. I thought there is always a voltage drop associated with resistors.

 

[Wurf]

Current flows from the Cathode to the anode on a Diode. The stripe marks the Cathode. Based on the image from the OP and instructions on how to install it, this would only allow current flow from connector side to the sensor side. There is a voltage drop accross the diode but you would need to know the current flow to calculate it using known formulas.

Just google search "calculating diode voltage drop" and you'll find more info. I think the drop is probably the key and the resistor values others have used in the past were possibly not right. I think the black wire is positive and the white is the signal wire and if you have a three wire heated O2 sensor the other wire ( red? I forget ) would be to apply voltage to heat the sensor. I really don't know what kind of O2 sensor these cars use however.

This trick of fooling ECU's into thinking there's still a O2 sensor connected is common with many brands of cars but you guys already know that I'm sure. I think the diode simply gives the ECU the proper feedback it's looking for vs a resistor. The drop would not be as linear as a resistor I believe. I could be wrong about that. Been a long time since I took a solid state class!

 

[RichB]

I think the ECU is able to detect the voltage drop from a resistor by how it accomplishes it. If you put enough current through the system, the resistance would no longer be a factor.

A diode is able to beat the ECUs detection methods based on how it creates the voltage drop.

Thats all I can come up with.

 

[wanna3]

what i dont get is how everyone had a cel while ive never had a cel when i installed my obx header, iono maybe im just lucky heh

 

[Listers]

anyone leave in their nonfouler and also do the diode? i know trying to remove my nonfouler will just lead to the purchase of a new sensor

 

[blh_wakeboard]

Well Just had my emissions and safety done this weekend. With my catless exhaust and the diode in it, passed the test with flying colors(In my state they don't put a sensor in the exhaust tip and measue it, they just plug the computer into the obII sensor and test it from there). Been driving with the diode fix for 2 months now with no problems, the fix works great!

 

[barakelium]

what diode should I but for this fix? the pictures no longer work

 

[barakelium]

wow this is an old thread. sorry I didn't see it earlier

 

[barakelium]

what diode should I but for this fix? the pictures no longer work