Out of ALL the older vehicles I've owned, OBD-0 to OBD-2 Has ALWAYS shown the cell, from Honda, Lexus to Chevy and all between..
So recently picked up a '01 Dakota base shortbed, 4cyl 5spd. 189K. Prev owner kept it clean, but mechanically not so much. Also had a previous fire that scorched the back engine harness BUT still started, idled and doesn't smoke. (you'd never know until you start looking around under all that silly air cleaner/muffler) It was showing both oxygen sensors bad. And 2,3,4 showing melting I decided to order the upgrade 4-hole injectors, that I've installed in the past and had pretty good results.
Well, along with those, I just installed a header because original manifold had cracks. And the header fit without modding the A pipe or anything. So I'm happy there..
Added the new sensors and cut off the HUGE muffler that was added at some point, and sounded like there was a bucket full of rocks in it. The aft sensor is now only about a foot away from the end of the pipe now. So, with all that I'm thinking the aft sensor will throw a code. But since they're heated, do they self clean or heal? or do they just crap out and that's it, once they throw a code?
And do these truck owners that have 2.5-3" pipes, do they throw codes all the time because the exhaust isn't as restrictive and just ignore the light?

I have read through several posts, but it's mostly said to author is what the codes mean and to just get new ones. The Lexus that I had seemed to "heal" itself and shut off the code every now and then. But it's parked at the moment, and making this Dakota the daily driver.

Please let me know what you guys think.. I'm old school and still learning.
Thanks

 

I recall having to clear emissions related codes when attempting fixes. Just clear them and if they don't return, you're good. The only folks who will "ignore the light" are those in states without emission testing.

 

Yep, Mississippi doesn't require emissions testing any longer. But I really don't want to be hurting mileage either.
I just brought 3 4-wire sensors to work and wire brushed them and hit them with a oxy/propylene torch to a quick "red" and that's it.
Again, the subject is a 01 dakota base 2.5. It would be interesting to see if DIY.com has any "kits" to make a micro-squirt system for it.
I mostly drive highway where 70 is the limit. I have yet to get it on the road, but should be there in a few days. So from experience,
I find that around 57-62mph seems to be a sweet spot in cruising in most all my vehicles..

I did install brand new ones, so we'll see if any codes get thrown after a warmup.
If any others have knowledge with O2 sensors, CHIME IN...

 

On the 01 ECU, the downstream is only checking for a NoX value less than the upstream shows - or fundamentally, the downstream wants to show leaner than upstream. that's how it measures "Catalyst Efficiency". However it can't be removed from the pipe (99 and older can) because extra checks were added to see that the downstream poperly follows when the engine is deliberately ran extra lean and exta rich, specifically as an O2 test. If the downstream doesn't follow those tests, it will thow a code. In theory since the exhaust is bobbed it may or may not throw a code for that, as it's still getting a valid exhaust pulse but reversion properties may pull in extra clean air that wouldn't normally be there.

 

Great, and thank you for your response. But say the aft sensor throws a code of extra lean because of the "bobbed" pipe, and then at a later date add a less restricted muffler (2.25" louvered glasspack) then the rest of the pipe to the stock rear exit..
(past rear tire) Will it continue to "analyze" and make adjustments, removing the cel issue or No(?)
I can see if a sensor was getting oil/coolant smoke blowing over it for thousands of miles. But my original question is if these "heated" sensors can/will keep trying to get the best emissions?
I think I'm going to pull the new ones back out, and put the original ones that I wire brushed and "torched" to se if it immediately throws a code or not.
(I really need to get my own code reader/scanner for all the projects I have..)
also, I'll be going through YouTube for any vids addressing this. THERE'S GOTTA BE SOMETHING OUT THERE!

Thanks again.

 

The sensors are always listening. "Drive Cycles" are how the sensors are evaluated. you can fix the issue or change something, and the CEL will stay on even if things are corect and happy - the CEL will clear when a full drive cycle has been completed in "good standing", ie no pending codes while the stored code is active. Same with changing the O2's, you can switch them but the CEL will stay on until the drive cycle is satisfied in good standing.

Or, just unhook the battery, drain all capacitor charges in the module, then hook battery back up.

 

Something's WAY OFF!! now getting 0171, 0505, 1494. (I JUST LOVE ELECTRICAL)
Going to swap out back to the original O2 sensors to see if that helps. And welded the sections together along with adding a 2' glasspack to the end. So that makes the end about 2.5' from the aft sensor. (Is that far enough away?) Once I get it driving, I can weld on the rest of the tail-pipe because the glasspack is the same length as the one I removed.

I went with a inexpensive header (4cyl-Ebay) that was a direct replacement, because the original had severe cracks front and back. Then I had to double the center 2 exhaust ports gasket because it was leaking towards the loom right above it. Started it up again and sounded like a rod knock!! (WTH..??) then after about 2-3min of running like poop, it smoothed out (no knock) but now climbing to 3000rpms! The pipes started to glow,
so I didn't want to use brake-cleaner to search for leaks. Plus it was already dark 9:00 and the mosquitos were feasting.. I couldn't feel any exhaust leaking (puffs) where I could stick my hand. But might have to pull the manifolds again and see how flat they are. Might have to double up the intake gaskets..

And where is the "Leak detection" pump? up by the battery?

 

I'm going to guess yours is underneath somewhere down by the gas tank. Mine (quad cab) was under the truck, below the driver's seat. Just get under the truck and follow the evap hoses.

 

P0171 (M) 1/1 Fuel System Lean A lean air/fuel mixture has been indicated by an abnormally rich correction factor.
P0505 (M) Idle Air Control Motor Circuits SBEC II
P1494 (M) Leak Detection Pump Sw or Mechanical Fault Incorrect input state detected for the Leak Detection Pump (LDP) pressure switch.

Glowing headers and elevated idle is a vacuum leak in the severe lean direction. 0505 doesn't have a troubleshooting or noted section. "SBEC" is just an internal DCJR acronym for the PCM.

 

Thank you guys for taking the time to reply. I had to step away from it for a bit.. But the leak detection pump looks like it's right under the fuse block by the battery. Actually, there's a couple 'things' that look like it from the Rockauto site. Right to the front of the battery and under the fuse block, above the left shock.
I'll get back out there tomorrow and pull the manifolds again.