Car computer, online diagnosing, scans, ---

Hi, 2WD LTD 1999. I know a little about the mechanical features but am quite low on the electronics, online diagnosing, etc. Could you help with the following?
1. Where is the onboard computer port located? Do I need to periodically determine if it is functional? If yes, how can I do that?
2. Is this the same computer that helps with the computer codes?
3. Is it possible that the wiring for the check engine light may not be able to bring it on even though there may be a fault somewhere else?
4. I have replaced the battery in the past at a garage but I do not remember the mechanic ever readjusting the check light. How can I know if the battery replacement time has affected the computer's functioning?
5. I tried looking for the scan tool port on the left driver side, near the footwell, there are some ports there but I didn't know which particular one.
Thank you very much.

 

1. See picture for the OBD2 port location which gives you access to hook up a code reader to read codes.



2. Yes.

3. Very slim chance, but a code reader will tell you if the ECU (Engine Control Unit) has any faults recorded regardless of the CEL (check engine light). Bad people have been known to sell cars with a removed CEL.

4. <removed, see below by PhantomTweak>

Regardless, get a cheap code reader and it can clear the CEL and you can run the car and if it comes back, you know you still have a problem.

5. Another pic:

 

Sir, I cannot but appreciate your help every time, even on issues that others might consider mundane.

 

1. Located in the driver's footwell, right of the pedals, front of the center console area. Behind the centr console plastic. Does that help?
2. Yes.
3. If the wiring is bad to the check engine light, yes, it won't bring it on. If the bulb is bad, much more likely, it also won't light up. When you first turn the key on, before you start the engine, the CE light should come on like all the other warning lights. If it doesn't, probably a bad bulb, but not invariably.
4. Removing the battery power to the systems will affect the CE light. It will clear all the codes that will light up the CE light. It will also clear all the various computers memories, so any codes they have stored will probably be gone. Most also require 2 trips to set a codes they had stored again. Toyotas 2-trip logic it's called. It will also clear off any way's the computers have learned on how you drive, the environment you drive in, and so forth. They will then begin the process all over again.
The codes can also be cleared out by a manual entry on ttest sets plugged into the OBDII outlet. The technician testing the vehicle can do, or, if you have a test set of your own. They are available from most autopart stores, some as low as $20.00, and up from there. Most dealerships have sever sets worth up to $

 

Thanks!