Thanks guys.

Electrical issue with KOEO makes sense, guess it's time to change that sensor. Common sense tells me that with the time that tube was off (see previous posts above), weather (humidity and whatnot) got in there and corroded something.

I did also replace the transmission vaccuum diaphragm a few days before I got these recent codes (336, 337). No chance that's related?

Also, I looked up the sensor part on Advanced Auto Parts (they have local stores). For a 1994, they come up with two models, one has tubes one in front of the other (when looking at the part from the driver side of the engine), $80. The other has tubes that are side by side, $50.

Of course, the one on my truck has them front/back, $80.

Another local parts place told me that the side by side ($50) model is what's listed for a 1994, and that the front/back model ($80) comes up for 1993. He theorized that mine could be an "early 1994."

If they are functionally equivalent, I'd get the cheaper one. Anyone know if those parts are interchangeable?

Did I mention that I hate part swapping...

Mike

 

Hi guys,

Replaced the EGR sensor with the $80 one. CEL is gone again.

Thanks again for the help!

Mike

 

You're never going to believe this, but 6 weeks later, the CEL is back, and the code is 327 (KOEO and CM), still in the EGR/DPFE family...

Any ideas? I've replaced the rubber tubing and the DPFE sensor itself. The CEL went away for 6 weeks or so, just started up again last week. Are there more parts to be looking at here?

Mike

 

As I said, KOEO codes, because they are set with the engine off, pretty much have to be electrical. Are there more parts? the DPFE circuit consists of the PCM, the DPFE sensor, and a string of wires/connectors. Those are pretty much the parts to be looking at. A bad PCM is usually diagnosed by process of elimination (If every other possible cause is eliminated, the PCM must be at fault). If I think about it hard enough, I could conceive of some issue with the vacuum hoses to the DPFE causing a KOEO code, but that might be a little bit of a stretch.

Do you have access to a good diagnostic manual? I've seen them at public libraries and such, usually in the reference section. A good diagnostic manual will give you a detailed diagnostic procedure for each code. When you come up on something like this, sometimes these manuals can help, because they help you correctly organize your diagnosis, and identify all possible causes (I've seen a few interesting scenarios come out of those manuals).

 

Thanks mrshorty.

I agree, electrical makes the most sense, and I do remember you saying that before about KOEO issues. No, I unfortunately don't have a good service manual. I did see a post somewhere that got into using a vaccuum pump to check the EGR system. I don't have one of those, nor the experience to know how to use it.

So, I think with my limited knowledge and tools, I can do one of two things:

1. Pay someone to diagnose and repair this, and hope it doesn't throw another code after any warranty is expired (I seem to be on a 6-8 week stretch between EGR-related codes).

2. Suck it up and part-swap everything in the EGR system, including the valve and all vaccuum lines. I really, REALLY hate part-swapping, but this might actually turn out to be less money than bringing it somewhere, especially since I've already done the DPFE sensor.

Oh, one more thing. I did notice a rubber line all cracked and looking like it leaks. It is connected to something rectangular (which has two round ****-looking things on top), right behind the washer fluid reservoir. The other end goes to something (which looks line a sensor with a wire connection) near the DPFE sensor. What does that line do? I'll try to post a picture later if you need me to.

Again, this is a 1994 4.0L, A4LD, if that helps.

Mike

 

Code 327 = " EGR, EVP, PFE, or EPT signal voltage too low".

At least it's a different code.

I'd fix the crack in the vacuum hose. Any vacuum leak at all in the EGR system will trigger an EGR type code, and there's a good chance that hose is leaking.

Other than that, try unplugging the electrical connectors and spraying with WD-40. A poor connection might give a low signal voltage. If you can determine the signal wire(s) with a multimeter, you can isolate the circuit. Only 3 choices will be 5v source, possible ground wire, and signal wire.

 

"At least it's a different code." Now THAT'S funny!!!

Any idea what tube I'm talking about? It's connected to something that is right behind the washer fluid.

I will definitely fix that, but would really like to know what it is...

Also, what would the WD-40 do for this problem? Should I be cleaning the contacts and using electrical grease?

Mike

 

Mike, your original problem was "voltage too high" with the DPFE sensor, right? Then you replaced the sensor and it ran good for a few weeks, and now gives a code "voltage too LOW"......it's like the old sensor was shorted, giving a full 5v signal, and now the new sensor (probably) has an open showing 0v (and giving the LOW voltage signal.....? If the sensor has 2 wires, one will be a 5v reference, the other is the signal wire having something between 0-5v on it. I'd take a voltage reading on the 2 wires and see if this is true. Assuming the wiring and plug-in are OK, it sounds like the new sensor may have gone bad.

I looked on mine, and it dosen't have the unit behind the washer fluid bottle that you describe. I'm guessing that it has something to do with vapor emissions control. Might not have anything to do with the new code.....?

 

OK, I'll try to get a meter on it this morning.

One thing I am noticing is that every time I try to disconnect an electrical connector on this truck lately, one of the locking tabs break off. This has happened on lights, under the hood, etc.

Why are these so brittle, and is there anything I can do to avoid this?

Also, how do you fix them after they're broken, other than cutting and splicing in new ones? Is it worth it to do that, or is that inviting future problems?

BTW, I took some digital pictures of the tubing components I'm trying to describe. How do I get them up here?

Mike

 

Yeah, I've broken my share of those too. If it looks like the connector will be loose, I cinch it up with a small plastic zip-tie.
You can fix anything with zip-ties, duct tape, and WD-40.

 

Zip ties, yes... Do a search for my posts, I'm sure I mentioned somewhere that's what's holding my MAF connector together...