I am uninformed to what the ECU and OBDII terminals do exactly, I did use it to find me real mileage and such, but Im wondering what other uses they are for and how to operate it, it seems their are fault codes, the thing is, I dont know what their for or how they are used, and how the system checks for faults in your vehicle. I wanted to learn how it works, can anyone tell me how this all works? Much appreciated, oh and another thing, I am also trying to learn about this so I can get my check engine light to turn off

Thanks in advance.

 

Hi Yvo,

ECU (a.k.a ECM, etc...) is the computer that controls engine, brakes, transmission, A/C, whatever requires sensor inputs. The ECU receives signals from sensors and then calculate the output to control various systems. ECU has programmed values and if the sensors send values that are not within the programmed values (e.g. voltage too high or too low), the ECU stores a fault code. ECU'sare often referred to as "black box" and are usually not user-serviceable for their complexity (but on a few occasions, electronically-inclined people can open the box and troubleshoot & repair).

OBD-I (OBD: On-Board Diagnostic) is the older generation of self-diagnostic system. If there is an internal fault, the computer (ECU/ECM) can find it, store it in the memoryand report it to the technician/user. The good thing about OBD-I is that you do not need a special code retrieval tool to read & reset codes (there may be some exceptions).

OBD-II is the current version of self-diagnostic and you must have a special equipment to retrieve fault codes. For Volvos, there is a socket inside the car where you can attach the tester (OBD-II scanner). OBD-II scanners are capable of retrieving fault codes & erasing them, though cheap scanners have limited capability and most aftermarket scanners can only access engine & its related codes. Some advanced units, that connect into a lap-top, seem more capable. Auto parts shops, such as AutoZone, have the scanner and can retrieve the codes for free and erase the codes, except for emissions-related codes.

Some useful links:
http://www.troublecodes.net/Volvo/
http://volvospeed.com/Repair/a1.html
http://volvospeed.com/Repair/a2.html
http://volvospeed.com/Repair/a3.html

Actron is one of the major brands for OBD-II scanner:
http://www.actron.com/

I hope this helps.


JPN

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Thanks very much JPN this helped a great deal.

People like you really do amaze me of how you can take time out to make such elaborate posts and help somebody else with every problem that you can possibly combat. Your my favorite one on this forum, keep up the good work, we all appreciate it. Now Im going to go out to my car and test it for fault codes! Thanks!

 

Hi Yvo,

I'm glad it was of some use.

>People like you really do amaze me
I learned it from my American friends (including those on this forum). It was highly influential.

See you around,


JPN

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