EGR (and OBD) Readiness Questions

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Mar 8, 2011
Birmingham, AL
EDIT: Post #11 is where I'm at as of 8/2/2012.


EDIT: See post #3 for a disgruntled update.


Another EGR delete thread!

Not really, I need some additional clarification on the issue of OBD readiness related to the EGR resistor mod. I am particularly referencing this thread along with the many other EGR delete threads. Thanks again to SuperHatch for great research. Anyway, to the question...

I've been throwing the 0401 code for a while, and am going to put the 4.7k 1/2 watt resistor in the temp sensor. However, I want to maintain OBD readiness. My question is this--under what conditions will my OBD system stay ready? Some related questions are:

-is the system ready now, despite having the 0401 thrown? I assume the answer is yes, but would like confirmation.
-if I just put the resistor in now, will my OBD system stay ready?
-if the code is cleared prior to installing the resistor, will I maintain readiness?

My present through process is if the system cannot do the EGR test and see both hot and cold temps, then I will not be ready. Since I've thrown the code, it will want to go through the test to verify EGR readiness, and when it fails due to the single resistance, readiness will fail. Is this correct?

Lastly, if I build the circuit SuperHatch describes, can I just use the connections at the VSV and EGR temp sensor under the hood rather than vampire clamping at my ECU? If the VSV and EGR temp sensor will be deleted anyway, why not tap them there rather than get at the ECU?

Does all this make sense, or am I just smoking rock?
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Seeing no response, I figured I had to go answer this myself. I put the 4.7 1/2 watt resistor from Radio Shack in Thursday night and headed over to my local Advanced Auto to get my codes read and cleared. I expect I'm only throwing 0401 and really just need it cleared, but I digress.

I got to Advanced and they informed me they quit reading codes at the first of the year! What the do-do!?! Said the EPA recently passed some regulations about who can clear emissions codes, so Advanced Corporate decided they'd quit reading altogether to avoid any turbulence at all. I called my local Auto Zone to see if they still read codes, and they do. But, they won't clear them.

I dunno... perhaps they were never supposed to be clearing them, perhaps this is nothing new, but it messed up my world since the Advanced is a quarter mile from my house and the Auto Zone is about eight.

So, any recommendations? Anyone in the Birmingham area have a OBDII tool and want to do me a favor? Just buy an Scanguage? I just wanted to get my 0401 cleared and be sure the OBD system remains ready... I guess that just won't be easy to do.
Sorry to hear all the headache. I have a P402 and for the first year of ownership I'd just checkout the OBDII scan tool occasionally at an O'Reilly (to check and clear myself) but that got old and I picked up the Ultra Gauge around this past December... it's been worth every penny.

I'd strongly vote to just buy a UG. The price isnt bad, much cheap than a scangauge. Even beyond codes and clearing, the other features are great IMO. Just checking temps for example has been worth it too. Good luck man.
You can clear codes with either the Scangauge or the Ultragauge, correct?
Once a code is cleared, system goes into non-ready until all parameters are met again. It may stay not ready forever with the resistor mod.
Ah, so I do need to construct SuperHatch's readiness circuit if I ever want the system to be ready again using the resistor mod.

Sounds good... off to Radio Shack tonight I suppose. Still have my issue with reading and clearing codes, but that's really another matter altogether.
That's exactly what I need to do, but unfortunately I'm in ATL for training and won't be back by then. Does anybody ever bring their kids to the meetings? Many times, taking a kid (or three) with me is a prerequisite for me leaving the house...
I am also running a 401.. I live in Atlanta advanced reads codes and they let you hit the clear tabs yourself.. If you have your 450 here just doit in ga. But you will probably have the 401 by the time you get back home..
Update on my issue here...

I have been running the 4.7k resistor for a couple weeks. I cleared the CEL by disconnecting the battery (I know, I lose valuable code info but I'm pretty sure the 0401 was the only one thrown). I finished the readiness circuit last night using the theory described by SuperHatch. The differences are that I used 220k ohm and 2.2k ohm resistors rather than 200k and 2k, and I connected it all in the engine using the VSV and temperature sensor plugs. For a relay, I used a Toyota one I pulled some time ago... it's used in fog lamps in Celicas, among other applications.

Anyway, I hooked it up earlier and let the LX run just to be sure that it wasn't going to blow up before I left to get the code read later. I put the 4.7k resistor back in before I left for Auto Zone. My thinking was that I wanted to see the scanner say the system was not ready, then put the readiness circuit in, drive for a few miles, and then rescan to see if the system was ready.

When the first scan was made on arrival, the scanner read no codes found or no codes present or something like that. I expected to see that the system wasn't ready. So, my questions are:
- is the system ready and all is fine and dandy?
- is Autozone scanner too cheap to tell you that the system isn't ready? I would think even the cheapest scanners should tell you that.
- could installing the circuit for just a few minutes while the LX was just idling be enough to ready the OBD system? If so, I suppose that would suggest that, when the OBD finds the EGR system not ready, it prompts it to cycle through its readiness check right then and there. If so, then it probably went ready at that point.

Once I get some clarity on the above questions, my plan is to drive it for a while to be sure that everything functions as normal long term. Then, I will remove the EGR equipment and block off the ports. I'll do a write up with pictures if anyone thinks that will be of value.
Not all codes readers show readiness status, SG2 does though. It takes a couple hundred miles to cycle through its parameters also.
It takes a couple hundred miles to cycle through its parameters also.

Meaning I need to leave the readiness circuit in for a few hundred miles to achieve readiness?
You first need to track down a ODB2 scanner that will give you the information you need. Do some research online to which particular model you need before you go so you don't waste any time.

Go to Harborfreight or whatever Autozone and buy one. Return it later if you feel you don't need it afterwards but I always feel they are a good tool to have in your truck at all times.
I'm trying to scrape by with this project until I get such scanner. I understand the bluetooth OBD scanners and a smartphone will give me what I need, and I'm inheriting an iphone from a friend... only I don't have it yet. Hoping for it in the next week. Bluetooth scanner will be on its way shortly after that. That aside...

To the other question, after thinking about it, you mean that the scan guage takes several hundred miles to go through its parameters, correct? Not the ECU's OBD readiness check, I assume. And thus your statement about getting the right diagnostic tool?
The ECU in the car could take a couple hundred miles to set all parameters to show readiness. Sometimes faster. This is why for states with readiness testing, if your car shows not ready, they tell you to return in a week or two, not usually the next day.

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