what is checked on a car when it is tested on a computer?

Question

The check engine lite is on, mechanic is going to put it on computer. I understand that.........my question is, if something else besides the check engine prob is there will that show on this computer test?

Answer 1

The Check Engine Light (CEL) comes on when there has been an out-of-spec reading from one or more of the many emmissions system's sensors and/or computers, usually for a set number of test cycles.

The tech will pug into the OBD (on-board diagnostic) with a scan tool. There will be a diagnostic code recorded, which according to the manufacturer's fault tracing procedure, will give the tech a test procedure to follow to determine the fault or faulty component.

It may turn out that there is nothing to repair, the tech will clear the code, the CEL will go out, and you'll be on you way.

On the other hand, it could be a control unit (computer), wiring harness, manifold leak, etc., and could cost thousands of dollars to repair/replace.

Good Luck....

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Answer 2

A common misconseption about Scan tools are that they do not tell you what is wrong with the vehicle. They do however store fault codes in a data bank in the vehicle computer. When the scan tool is hooked up the technician is able to retreve these codes. However. Most codes can be set off my many things, a single code can have more then 50 problems that could possible set it off. After the technician gets the code, he had to diagnose what the problem that is setting the code off. Sometimes its easy to find, soemtimes its not. All the codes do, is tells the technician what the problemed system is, and that gives the technician a place to start. If there are multipul codes, that is quite often the case, these codes can be read and if they are in the same system they can be used to narrow down the problem, yet at times multipul codes in a system just complicate the problem.

Any code that is an engine related code will be stored in one databank, any transmission codes will be stored in another databank, any ABS codes (if the abs light is on) will be stored in another databank, and any codes that are SRS or related will be stored in another databank. Most of the time, you do need special Scan tool to be able to ender the other databanks.

Codes don't tell what exactly is wrong, they tell you a place to start looking. Without proper doagnosis a code is useless.

Answer 3

really that phrase is kinda decieving. on todays cars there are multiple computers. sometimes over 20, depending on vehicle. when we "hook up" we are installing a scantool.
at gm its known as a tech 2 for OBD2 systems.
OBD is for 1996 and later.
the computers are already there so to make it simple were using a screen and a keyboard. this gives us the ability to
see what the computer see's. and with the keyboard we can
manually turn on or off things. now dont think were installing a
full sized keyboard and some 17 in monitar. a scantool would fit in a shoe box
we use the codes like one i had the other day on a 03 yukon
code P0101. a mass air flow sensor performance.
a problem with the manifold absolute sensor was causing this. and the bad reading was caused by a restricted catatlytic converter. now there are codes for a cat conveter but it wasnt giving me one and i had to use the readings i was given to figure it out. sometimes its not easy.
we dont use these much anymore but there is a tool known as a digital ocilloscope. this a large tool that has lots of wires and we hook them up to specific wires that can give us views of digital signals like wave form patterns, injector pulsewidths, and so one. nost of these can be seen on a tech 2 now.
i hope i didnt just ramble and answered your question

Answer 4

Usually when the check engine light comes on, always check to see if you put the gas cap back on tight enough. Take it off and put it back on really tight. Then, after the car is turned on and off for about 20 times, the light should go off. If it is still on, then do the computer test. Just checking the gas cap can save you a few bucks.

Answer 5

the car has a on board computer,
the function of this computer,control the car system in general.
engine performance
transmission performance
personals safeties.from exhaust gas recycle ,up to collisions protections

this on board computer "read" the car's sensors(all over the car) to"see" if one of them is "saying" that something is wrong.if something is wrong then the computer store in memory a "faulty code"
and that is what , the mechanic gonna check

Answer 6

The computer that the mechanic will hook up to your computer will tell him exactly what is wrong with your car. Just like your PC is self diagnostic. Your car has a computer in it that can tell your mechanic's computer what its problem is. There may be a number of things wrong with your car, and the computer may spit out a list of things.

Answer 7

Check engine light could mean anything, egr valve(exhaust gas recirculation) computer needs resetting there will be a code that will print off or be on the screen and they will tell why that light came on.

Answer 8

sounds like your Voltage Regulater needs replaced but the place where i take my car to get a computer diagnostic test done is only $ 40 hope this helps good luck

Answer 9

its not a computer, its a scanner and what it does is several things but the two most important ones you need to know is, read the DTC's ( diagnostic trouble codes) and look at live data that your sensors are feeding the ECM ( engine control module)

Answer 10

The computer test which is done with an OBDII scanner scans everything electrical with your car..... oxygen sensors and all. Even transmission electrical problems too.