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[[email protected]]

I'm sure there has got to be a few auto mechanics here. Hopefully someone has some insight.

My wife drives a '05 Chrysler Pacifica. Its got a 3.5L V6. About 105K miles. In PA, we have to have our cars tested for emissions to pass a state inspection. Its an automatic fail if the check engine light is on.

Well, its time for the yearly inspection. The check engine light has been on all year. I had the car scanned by a couple places and it is throwing out the code "catalyst efficiency below threshold"

I replaced both o2 sensors a while back (no help). I replaced the catalytic convertor last night. I installed a Eastern brand, direct fit replacement. The light was off for maybe 20 miles and came back on this morning. She says the car is running much better though.

So, other than replacing o2 sensors and the cat, is there something else I should be doing to get rid of this trouble code?

 

[RaWarrior]

Catalysts need time to "break in"....we worked with Emitec for custom catalysts on our SAE clean snowmobile up at school, and they said typically they need ~1000 miles/ 50 hours before they reach peak efficiency. Driving "hard"...lots of throttle can actually accelerate this(we went out and rode our snowmobile WOT for a few hours). So go hot-foot it around for a bit.

Give it some time and see if the light goes off again.

Though, I've also heard the aftermarket cats can be hit-or-miss. People flock to them because they're cheaper than OEM by a good chunk, and depending on vehicle, age, how well the motor actually runs, ect, some people still get the "efficiency below threshold" code. Aftermarket ones are often "performance" cats, which by nature are less restrictive and have less catalyst surface area, and aren't as efficient.

Otherwise, there's not much you can do. The car gets plugged into the state computer, and your car's ECU keeps a record of access....so they'll know if you just plugged a scan tool in and cleared everything in the parking lot. Won't even matter if you remove the bulb from the MIL....the code will still show up on the computer.

 

[sarchin]

The problem could be a number of things, unfortunately. This happened on my minivan and was the charcoal canister that is underneath the drivers seat. The fitting for the vacuum line gets destroyed as a result. I know it's time to replace the line when I can start smelling gas. The EGR system works with the charcoal canister so check your all your vacuum lines too. I usually spray carb-cleaner around the fittings to check for loose connections.

 

[jfeagins]

I take it the new code is the same as the old one which indicated the cat system was bad?

Seems like every time I get one thing fixed on my car, another thing entirely goes haywire.

 

[Woody]

clear the code just before you get it inspected.
no light no problem for them to see.

 

[Ebein_486]

When the tech starts the car the check engine light wont come on and he'll know the bulb is bad and pull the OBDII codes and see them anyway.

 

[sdt354]

clear the code just before you get it inspected.
no light no problem for them to see.

Won't work I'm afraid. State computers show run time since last code cleared.
Steve

 

[acammer]

Won't work I'm afraid. State computers show run time since last code cleared.
Steve

+1, you have to have completed a drive cycle and have the obdii tests completed. Did you use a good OE O2 sensor, some times the cheap ones dont work so hot. For a rear sensor, just get an O2 simulator, I have used a few in hot rod toys that don't have cats and they work just fine.

 

[[email protected]]

The new o2 sensors were Bosch.

 

[acammer]

Sounds like a decent sensor. How is the exhaust system otherwise, up-stream of the cat? If you've got any exhaust leaks, those will play absolute havoc with O2 sensors. A little exhaust leak will introduce extra O2 into the exhaust, and throw things off. What is the specific code? (example - P0137 02 Sensor Circuit Low Voltage (Bank I Sensor 2))

 

[[email protected]]

Don't remember the code #. Catalyst efficiency below threshold bank 1, and bank 2. No mention of 02 sensors.

Only 3 gaskets in front of the cat. One on each manifold, and one where the manifolds merge. I replaced the gasket where the cat meets the Y pipe or whatever you want to call it. After starting the car I left it jacked up and checked around. I did not notice any leaks.

I figure I will take it and have the code scanned again, have them clear it, have her drive it for awhile and see what happens

 

[Rusty McNeil]

The rear o2 sensors only job is to report on cat efficiency, the front ones job is to talk to the ECU and modify a/f according to the ECU logarythms (sp?), making it a closed loop system......

If you can find a o2 sim that works it should solve your problems, I had hell finding one that worked for my wifes supercharged 350Z (read couldn't) that had no cats at all, since the ECU on that car is constantly tickling the a/f and expecting the results to show back up on the rear sensor.... a simple sim with a constant output wouldn't work....the Nissan was too smart for that.......But I have had them work on a lot of GM products.....I think the LEV or Ultra-LEV vehicles are the ones that are constantly "tickling" with the a/f to test the rear o2 sensor response.......specifically to keep you from cheating it I think.....

Another cheat that did work on the 350Z, was to buy some of those spark plug anti-foulers in the same thread size as your sensor, drill the smaller hole in one out, screw the sensor into that, and then screw the drilled one into an unmodified one and then the whole thing into the cat. It gets the tip of the o2 sensor out of the cat but lets it still respond to changes in a/f but do it more slowly and less responsively....It would reliably keep the light off for several thousand miles, but eventually a hard long run "on boost" with the a/f rich as fuck would turn it back on anyway, but easily reset and got through enough drive cycles for the ecu to read OK at inspection....

 

[tugla]

what is the actual code number its putting out? how is your fuel mileage? if its running rich for any reason like on a cold start cycle might give false cat readings and problems, i find with computer cars its not always the exact code but a under lining issue and that might be why you are chasing this issue. might have to look at other stuff like miss fires, egr, dirty mass air sensor. what type of air filter are you running? the oil form k&n can dirty up mass air sensor i've experienced that caused the light to stay on. i assume the basic tune up has been done and it runs tip top the van?

 

[[email protected]]

Never heard of using the spark plug anit-foulers. Did a quick search on that and seems like lots of guys have success doing that. If the CEL stays on for awhile I may have to try it. Thanks for the tip.

 

[tmosel]

The Chrysler Pacifica has 4 O2 sensors. One on each exhaust manifold and two at the converters.

And here in California what I do (I have a 1998 Accord that the check engine light is always on) is I disconnect the battery positive cable for 30 minutes. You will lose all of your presets in the radio, but it also wipes out the memory of the ECU and clears all of the codes in the ECU memory.

And speaking with a friend of mine that does smogs here, he tells me that if the car was just scanned and the ECU memory was just cleared he doesn't care. Who's to say that you just didn't leave a repair shop before going to get it checked?