Need some ideas here....

[Twizzler09]

Ok, so this morning on the way to work, I noticed that my truck was idling a bit rougher than usual.... so when I was on lunch I borrowed the Shop's code reader and I got the normal "P1443 Factory Controlled Auxillary Emission Control" code, but there was another one that I hadn't seen before "PO420 Catalyst System Below Minimum Threshold Bank 1"

The first code, P1443, I believe is something about the Evap system.... and the code reader seems to confirm my theory. It performs "Quick Tests" before you can pull codes and the Evap system came up as "Unavailable". Everything else came up as "Ready". Am I correct to assume that theres a sensor of some sort that deals with the Evap?

Now for the next one.... The only thing I could think of, was that the Catalytic Converter had gone bad and is no longer functioning properly. But its brand new as of July last summer. Whats the chance that it could have gone bad this soon? I asked one of the guys at work about it (he's been wrenching for about 34 years now...) and he said that since the Cat is essentially brand new, that he believes an O2 Sensor to be culprit in this case. Could that be accurate?

Appreciate any clues on this one

 

[Bruce]

I would think it it to be an O2 sensor also,could also be bad plug or injector maybe. Pull the data stream up on the scanner and see what the O2 sensor on bank 1 is doing, like staying rich or lean or is it oscillating between rich lean .

 

[MAKG]

It could be bad, overpowered, leaky (exhaust leaks), or poorly grounded. The downstream HEGO sensor might be at issue, but I'd check out other things, first.

You're at a shop; pick up a DSO or graphing voltmeter and connect it across the downstream sensor and see what you find. If it's switching, your cat is bad. If it's full lean, full rich, or out of bounds, you probably have a sensor problem IF the upstream sensor is working correctly. If it's normal, you probably have a wiring problem between the computer and HEGO sensor, possibly a loose ground.

If the upstream sensor is not switching properly, fix that before going after the downstream sensor.

 

[Twizzler09]

You say exhaust leak, this actually seems likely. For a long while now I've been able to hear what sounds like exhaust leaking from the Manifolds, and I did recently notice that the sound of said "leak" changed somewhat, and increased marginally in volume.

I have a new O2 sensor to put on it, and I'm going to take a look at the data stream next time I get a chance. MAKG, upsteam/downstream/HEGO Sensor... thats all mumbo-jumbo to me.... any chance you could explain the function of each and explain the testing process?

What about the Evap? Any chance that theres a sensor or something on it that could go bad, causing it to trip a code? (I'm pretty clueless when it comes to Evap systems and emissions stuff.... it all confuses the daylights out of me.)

 

[KELLY88]

I had EVAP problems a couple months ago. The truck ran fine but got a check engine light still. Scanned it and got the P1443 code. After doing a little research on this code both on here and a couple other sites (and having my mechanic tell me he wanted $120 just to test the system) I went and spent $35 at Auto Zone for a new canister purge solenoid. Swapped it out and the CEL went off.

 

[Twizzler09]

Sounds like as good of a place as any to start on the evap side of things, thanks Kelly.

Now, if someone were to explain the things MAKG spouted out, I'd be in even better shape

 

[97ranger4x4]

Yeh I would be interested to on a good explanation. I have had the P1443 code come on and by just pulling the canister purge valve and blowing some compressed air into it and clearing the CEL it hasn't come back on. Im guessing its time for a new cannister purge solenoid but ill wait it out...

 

[MAKG]

OK, OBD-II systems always have at least one "upstream" sensor (before the cats), and at least one "downstream" sensor (after the cats). The upstream sensor is for controlling the fuel mixture. The computer commands the injectors lean and rich alternatively over about a 1 sec cycle (sometimes a bit faster). You should see this in the upstream sensors as a discontinuous "switch" from lean (~0.2V) to rich (~0.8V).

The downstream sensor sees "cleaned" exhaust and should be pretty close to constant. If it switches like the upstream sensor, the cats aren't doing anything.

And HEGO = "Heated Exhaust Gas Oxygen." It's the modern name for an O2 sensor.

 

[Twizzler09]

Ah ok, thanks for the explanation.

So if I'm understanding correctly, if the upstream sensor alternates between rich and lean in a consistent, ~1 second or less pattern, its fine. If the downstream sensor does the same thing, means that the Cats have gone bad.

Now assuming the cat is fine, what should I expect to see? Should be a constant volt reading, correct?

 

[Twizzler09]

Ok, so I was able to pull up the datastream when I was on lunch at work, and heres what I found:

Bank 1 Sensor 1 -> oscillates .1v - .91v

Bank 1 Sensor 2 -> No Reading

Bank 2 Sensor 1 -> oscillates .09V - .93v

If I am correct in my thinking, regardless of what the Bank 1 sensors read, the downstream (Bank 2) sensor should still read a constant voltage, as its after the catalytic converter. Which means I have to replace my Cat, again.

Now what I cant remember is, do Rangers have two O2 sensors on the manifolds? If there is supposed to be two sensors and one is non-functional, it would explain why its idled strange for awhile.

Thanks for the suggestions so far everyone

 

[97ranger4x4]

Okay so I have the P1443 code and went to autozone and picked up a replacement cannister purge valve. Click Here

I put it in yesterday and 20 miles later my CEL came back on! So I took it out and will put the old one back in since that is not the problem.

I guess what can i do now? I am looking at the factory service manual and it saws that the EVAP emissions components have been designed to exceed 120,000 miles or 11 years. well im over both. It doesnt really show how to test any of the parts. So I guess I have to replace each one individually until it works right?

thanks for any help or guidence on the issue!

-Keith