Scan tool question

[90NHXJ]

2001 XJ with the 4.0. I wrote about a week and a half ago about idle issues. The vehicle wanting to stall out on me at idle or switching to reverse. The check engine light is not on and it's not triggering any codes. I finally took it to the garage where they cleaned out the intake plenum and reset the parameters on the computer with their OBD II tool (I'm assuming.) Everything ran great but I was not optimistic that it was going to stay running fine. I was right. This morning it started up again after about a week of running fine. I know one of the sensors is not working right. Whichever one hasn't failed to the point that it kicks the check engine light on but is enough to throw the computer off a bit.
My two questions are: I suspect the TPS may be the problem but at $66 I don't want to just buy one for trial and error. What's the correct procedure for testing the TPS?
My other question is Sears has a computer for reading the codes for around $200 that I would like to get that has the ability to reset the MIL. What is the "MIL" and is that the same as the garage did when they reset the parameters on the computer? The garage had said that the vehicle would run different than we are used to because of that with possible different shift points. Thanks and sorry for the length.

 

[Ivan]

When my "suspect" TPS finally threw a CEL display on my '98 after some sporatic bouts of high idling, I took it to a local repair shop to have the codes read. It did come back as a TPS code P0121 (TPS voltage does not agree with MAP).

The shop even provide me with a print out from their on line service "Mitchell Repair Information Co, LLC) with the TPS test procedures printed out. As good as the instructions were; I took it on faith that the problem was the TPS, and it simply replace it. The TPS was my problem.

My point is perhaps the shop you took it to, can provide you with the same type of print-out information on how to test your TPS, or at least provide you with the error codes they picked up to narrow your problem.

 

[90NHXJ]

From what I understood it wasn't throwing any codes out. I figure they would have told me (based on the history I have with the mechanics there, and honest as all hell.) I think they just did what they did to try to correct the issue. Any idea what MIL stands for?

 

[lilredwagn]

MIL - Malfunction Indicator Light .. CEL - Check Engine Light
two acronyms, same thing. If I may offer some advice, do some serious checking before you drop $200 on a reader. They don't do much that the ~$50 Actron doesnt - they just have a lot of empty space in a big case to make them look "professional". The little one will read the code and display it in the format "P0101" and reset the MIL. There are several online resources (assuming the scanner doesn't some with a book) that will tell you that the "P0101" means "Mass Air Flow (MAF) Circuit Range/Performance Problem".

On the big one, you're paying $150 extra so that you can have a display that will tell you "P0101. Mass Air Flow (MAF) Circuit Range/Performance Problem"

..and can do it in Spanish and French too.

It also can read live data from the sensors, but that will not be of much use unless you can graph the data and review it later, and IIRC that's only available on the $400+ units.

If you have a laptop or PDA, you might look into adapter/software that will provide the features of the $400+ scanners for ~$200

This is the little one:http://www.amazon.com/Actron-CP9125..._1_4/002-0844363-9386413?ie=UTF8&s=automotive

In this particular case, it wouldn't have helped you at all, but it doesn't sound like the professional jobbie that the mechanic had helped either.

I don't have the TPS testing procedure for a 2001, but someone will chime in or it can be found with search.

 

[Saudade]

Like lilredwagon says......

I have a cheapie one too. it reads codes and resets them, tuning off the light. But you have to write down the codes and then go look them up to find out what it's telling you. Once you unplug it, you lose the codes.

The more expensive ones will do as lilredwagon says and often store the codes in the reader to refer to them "offline". There are also different protocols including the newer CAN. Many cheapie readers do not support all protocols.

So how many bells and whistles do you want? Really depends on what you want and how much you're willing to spend.