1994 toyota pickup code reading

Because your trucks computer is getting a signal from one of its sensors that something is wrong. Hook up an ODB code scanner to it and it will give you a somewhat vague reading of what is wrong.

the light will flash a 12 code 3 times then tell you the stored codes then a 12 code when the stored codes are read, so if you only see a 12 and the forth time is a 12 then there is nothing wrong with your truck. the 12 code is just telling you its in diagnostic mode.

orielly has a tester reader if u take to them they can tell you what censor it is

Well, that's the check engine light I think. It is saying something is not normal. You can read out a trouble code to give you an idea of why it is on. Turn the ignition on, but engine stopped, and with a piece of wire bridge terminals TE1 and E1 in the service terminal box, at one rear corner of the engine compartment.

The check engine light will then blink. A steady blink 4 times per sec is "all normal".

Trouble codes are 2 digits, and these will be blinked - first digit - pause - second digit - repreat.

So the oxygen sensor fail code (a common one) is 21, and will show 2 blinks - pause - 1 blink - repeat.

There are 22 of these codes

I would check for fuel,(pressure and injector pulse), spark, and compression, before checking any codes. Lack of any of these basics can result in codes, and then you waste alot of time chasing a symptom, instead of the actual problem.If more people followed basic diagnostics, which always come back to these three basics, rather than chasing codes first,they would find no starts much more quickly.

Of coarse it is still on

An O2 Sensor Code, does not tell you
to change anything.

You have a system malfunction to diagnose,
like a lean condition.

Study OBD 2 Systems on the internet, education
is the key

see:
http://4crawler.com/4x4/CheapTricks/index.shtml#TimingCheckConnector
(how to read codes)
and
http://www.off-road.com/toyota/tech/codes/index.html
(what they mean)

Do a search for the "check engine light" code. Attach jumpers to find out what the code reads.

Your mechanic should be able to read the codes with a special device he/she hooks up to your car's computer.

Your car has a computer that stores codes when something needs repair or maintenance.

The Check Engine light is on because the computer has a code stored in it.

What is you engine idling at if below 700rpm the pickup coil in the distributor will not send a good signal or one at all.

also unplug the 2 wire connector on the distributor and check resistance it should be 180-240 ohms.