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I noticed last week that my inspection sticker was two months past due. No big deal except Edgecombe County now requires emissions testing...grrrr. OK still no big deal because I have all the emissions stuff in place. The price was $40 which included an extra $10 to check my window tint.

This morning when I arrive at work my CEL is on . Off to AutoZone to get the code pulled. The code is P0420 "Catalyst Efficiency Below Threshold Bank 1". According to my FSM, that's most likely either the cat or the heated 02 sensor after the cat. Neither one is cheap to replace.

I did some checking into 02 simulators since their use is common among OBD-II vehicles using a test pipe, header, or high-flow cat. The one RK Sport and Jeg's sells Casper Electronics Model for my car is about $50. On the J-body board some say it works, some say they still get the DTC code. So basically it's a $50 experiment.

I did even more digging and ran into this. $5 Mechanical 02 simulatorThe idea is to slide the rear 02 sensor outward moving it from being directly in the exhaust stream thus making it's readings (and voltage) slower/lower. From what I've read in the FSM, the PCM compares reading between the two sensors. Things are normal and no CEL is caused if the second (rear) sensor is "sluggish" and not creating spikes in it's output voltage back to the PCM.

So what do you guys think? Does anyone have exprience with these? It looks like an experiment to see what works. The question is whether to go with the $50 or $5 one?

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Vincent Keene
'06 Ford Mustang GT (track rat)
'15 Dodge Charger R/T (yeah, it's got a HEMI!)
'07 Ford Fusion SE (205,000 miles and counting)
'98 Chevy Z-24 (retired)
'93 Acura Integra (Team SWB 24HOL Car)

Done both and neither work for me. Not sure if it is because of my lack of cat or if there are other factors. I may have just pulled too much from the emissions system for it to work, but at this time, the code for my AFR from second O2 sensor is always on.

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Rich
http://www.v8mongrel.com/

It's like déjà vu all over again.

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Has no responsibility whatsoever.

Vincent,

I have an OBD-II softare pack that's laptop based. It allows you to look at the O2 sensors individually. The one after the cat should be more stable looking than the one before the cat as the cat should help clean up the exhaust. Cat efficiency is also a big function of temp (IIRC they start around 500F and peak arounf 750F) so if you start the car cold and monitor the O2 sensors as it warms up you get a good idea if the cat is working. O2 sensors have the same problem with temp, but they now have heater wires.

If its a bad O2 sensor, I'm pretty sure you can buy one for $50 or less. It helps to have a split socket or crows foot so you don't have to cut the wires. Replacing a bad O2 sensor should help fuel mileage too.

Let me know if you want to use any of this ... of course its all in Raleigh.

Frank

Some of the Subaru guys use these after switching to aftermarket downpipes and such, and have reported success.

Cheers,
Anders

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Lina Racing: As Seen On Radio