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Hi all, this is my first post here, looks to be a helpful forum..
It looks like I need a new cat, after following Eric’s diagnostic video. My rear O2 sensor is switching voltages like my front O2 sensor. I will be selling my truck soon for a van, but still I don’t want to put in a horrible aftermarket part….because that’s a waste of money no matter how you look at it.
An OEM cat for my 1995 tacoma looks to be over $900 and an aftermarket is $250 for a California legal model.
Are there any brands to watch out for, or any way of evaluating long term reliability of these parts? what are other tests I should do to be sure it’s not my engine running condition that ruins my cat? I had a cracked exhaust manifold for quite awhile which I fixed first hoping that it would clear my P0420 code, well that needed to be fixed anyways.
Thanks
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Alrigth, great guys. I have the cat in some detergent water soaking right now, and I have minimal hope that will result in a fix, but I will update here with my results. From more research I leaned that it’s usually not the crudding up of the honeycomb that ruins the cat, it’s the breakdown of the metals or ceramic within it. So even if the cleaning did work, it couldn’t fix it. But it’s worth a try
I have re-installed my old cat that i soaked in laundry detergent :unsure: I am trying to make sense of my diagnostics but need some help
1.) The rear 02 sensor fluctuates from 0.1 v to 0.9 v in a nice sine wave, but the outlet of the CAT is at least 100degrees hotter than the inlet. Is this CAT bad? that’s conflicting results right?
2.) How strictly do you need to follow drive cycle instructions to reset monitors to ready? I performed the catalyst drive cycle twice and can’t get a ready mode. If it says drive 40 mph for 7 mins am I ever allowed to slow down or vary my speed? It’s pretty hard to find a stretch of road with no traffic around here that’s not the freeway. I’m not drivin 40 on the freeway.
3.) anybody know where to find drive cycle for a 1995.5 Tacoma? I am using data for a 96, probably the same but not sure.
The outlet SHOULD be hotter than the inlet, that tells us that the cat is burning things up. Now 100 degrees Farenheit sounds a tad low of an uptick, but that’s probably at idle? At road speeds it’s probably a bigger difference.
Find a state highway, those are often posted at 50MPH max, just drive 40 with your hazard lights and ignore the dirty looks.
Actually, it sounds like your cleaning might have worked. If the light stays off and you’re selling the vehicle, then you might be in the clear.
Keep us posted.
The behavior of the rear o2 sensor looks different than it did before. It used to fluctuate from .1 to .9 during all sorts of conditions. now it is a much tighter sine wave, but it’s range depends on how much throttle I give it. So at idle it’s between .1 and .18 and at around 2000rpms its between .4 and .6. And on a lot of gas it’s .7 to .9
Is that the proper way it should function? In Eric’s vid I just remember it was supposed to stay around .45 at 2000rpms.
Anyways, I still haven’t been able to set the catalyst monitor to “ready” after a few more attempts at replicating this drive cycle. So we’ll see. If the detergent worked I will be amazed banana:It will fluctuate a little, especially when you give it more throttle. The take away is that it should not fluctuate at the same frequency as the front O2. If it goes too far, it will be out of range and the light will come back on again. As for testing, you pretty much have all the testing that I would do in that situation.
Great, thanks Eric. I found out also that I was maybe misreading my scan tool, which lead me to believe the catalyst monitor was not “ready”.
I bought a Creader V and under I/M readiness it has 2 places it lists for the catalyst. In the first position it states
supp: not complete
the second listing says
stat: complete
I plugged the scanner into a couple of other cars with no probs and it always lists the catalyst “supp” as “not complete”.
I am guessing it’s just a bug with that model scanner, and “Stat” is the one I want to look at. I’m assuming they stand for “supported” and “status”.
I am very surprised if this fix worked. Thanks for the help and all your great vids!Damn, looks like Scotty is on to something!!
If you can get your scanner to plot the rear O2 (post-cat) voltage, it should switch quite slowly at idle or even at load. It should stay at one place for few seconds before switching. If your scanner can plot two, then compare it against the front O2 (pre cat). The rear should be switching way slower than the front one. If that is how it is behaving, then you have fixed it!
Please tell us if that is the case.
I am not sure about the speed of switching but the amplitudes are different. It was that the rear moved up and down in large swings like 0.7 volts but was very erratic. Now the amplitude is like .2 but it does switch in a sine wave. I can’t plot 2 at once, but if I get a chance I will take a photo of the two at hopefully similar conditions.
I’m going to have to try that method of cleaning the next time I run into that issue. Thanks for keeping us up to date. Let us know if things change.
I will keep you posted, I tried testing again last night to get some picks of the sensor output…it looked like it wasn’t working, the amplitude was big again. I will get pics up soon to get your opinions.
So are these good or bad readings? The images are the post cat o2. The front O2 looks normal I think, not much to interpret.
These are what it looks like on the freeway, which I thought were good.
[IMG]http://i42.tinypic.com/dxivcm.jpg[/IMG]
[IMG]http://i39.tinypic.com/orrm6p.jpg[/IMG]
[IMG]http://i44.tinypic.com/2z7iz5z.jpg[/IMG]
In the previous images the readings would stay in a high or low range depending on how much work the engine was doing…low voltage at low rpms etc
I need to get a pic uploaded of what it looks like revving in the driveway…stay tuned for that. Looking forward to your opinions
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