How/when does my car generate OBD2 Codes?

I'm thinking about buying one of those cheap code readers for my stang to see if I can get to the bottom of my idle and sluggishness issues. Before I buy one I have a couple questions to know if it will help me:

1) Can my car have codes present even if the CEL isn't lit?
2) If #1 is "Yes" - do the codes erase on their own after a while? (Like if the problem stops temporarily).

Thanks :cheers:
 
Cheap ones. . .. .

I've seen cheap ones for $29. They flash an led.

P0133 would come out as
flash. . . . . . flash flash flash. . . . . . flash flash flash. ..

I don't think you need real-time monitoring to get a code out. You don't even need the engine running.

I'm not sure how much the real time stuff in this unit will help anyone. Although I do like the 0-60MPH recorder. I have not tried it yet. I just picture stomping on the pedal and my laptop flying into the back seat.

The other nice feature is the software let's you look up the code.

One more tool I recommend is http://www.alldatadiy.com/

It's like an online manual. Costs $25 for the first year. Any additional year or car is $15. If you get a code, it gives you the trobleshooting procedure to find the problem.
 
1968cyclone said:
I've seen cheap ones for $29. They flash an led.

P0133 would come out as
flash. . . . . . flash flash flash. . . . . . flash flash flash. ..

I don't think you need real-time monitoring to get a code out. You don't even need the engine running.

I'm not sure how much the real time stuff in this unit will help anyone. Although I do like the 0-60MPH recorder. I have not tried it yet. I just picture stomping on the pedal and my laptop flying into the back seat.

The other nice feature is the software let's you look up the code.

One more tool I recommend is http://www.alldatadiy.com/

It's like an online manual. Costs $25 for the first year. Any additional year or car is $15. If you get a code, it gives you the trobleshooting procedure to find the problem.

Cool, I'll definitely look into that if I can't figure it out. Thanks again! :D
 
1. Those cheap ones don't really give real time data so you can't see you your fuel trim (which is 90% of the problems O2 sensor readings) There are 2 types of codes that is used in ODBII soft and hard codes. Hard codes turn on your CEL light and the soft codes are stored when the event happens and it is constantly checked over and over. If them problem doesn't go away it sets a hard code and there goes that nice light on the dash.

2. They do clear by themselves after you get the problem fixed and have 50 drive cycles..but who wants to wait so thats where the scanner comes into play and reset the light yourself.

3. Check out www.autoxray.com...they have a wide range of scanners, pricesand they are setup with US and Canadian emissions.
 
nex2nutin said:
1. Those cheap ones don't really give real time data so you can't see you your fuel trim (which is 90% of the problems O2 sensor readings) There are 2 types of codes that is used in ODBII soft and hard codes. Hard codes turn on your CEL light and the soft codes are stored when the event happens and it is constantly checked over and over. If them problem doesn't go away it sets a hard code and there goes that nice light on the dash.

2. They do clear by themselves after you get the problem fixed and have 50 drive cycles..but who wants to wait so thats where the scanner comes into play and reset the light yourself.

3. Check out www.autoxray.com...they have a wide range of scanners, pricesand they are setup with US and Canadian emissions.

Thanks for the info! I've just ordered one from eBay, it's just a code reader/eraser, I got it for $46, hopefully it's good.

Cheers :cheers:
 

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