Please help asap! Tranny swap, check engine light on only when start engine??

[yaldizzle]

Hey guys! Im trying to buy a 1995 240sx tomorrow and I guess it used to be an auto and it was swapped to manual but the guy is still using the stock auto ecu so obviously the check engine light is going to come on.

Now the problem is that I just found out that the check engine light is suppose to come on when u turn the key to the on position and then stay on when the car is started if there's something wrong.
Well with this 240, the check engine light does not come on when u turn the key to the on position but the light comes on after u start the car.
Isn't that weird? What could it be?

[alixander2012]

Was the tranny out of an s13? Could be the cas wasn't remounted on the new tranny.

[yaldizzle]

I don't know if it's the s13 tranny. That could be a reason why the cel doesn't come on when the key is turned to the on position?

[Hashiriya415]

Look at it another way.
What is a check engine light? Do you care? Does it matter?
If car runs great and you have no smog, then don't worry.
If you need it to smog, then it could be many problems that need fixing before it will pass smog. You wanna spend hundreds or thousands to fix check engine light? Up to you.

[zerodameaon]

If OC is Orange County then you need to get that fixed especially if its some back ally deal where he is making you smog the car on transfer of title which will be due right away. Try reading your codes to see what you get. It could be some hack job wiring for the swap so you want to check all of his wiring very close. Next thing is just to check continuity between the bulb holder and the dash harness connector. You could very well just have a short. Light doesn't come on when you turn the key to on because the circuits shorted but once you turn the car on whatever its shorted to now has power causing the light to stay on.

[AZ_BOY]

Dude I never seen my check engine light. It's there but off all the time. I don't care. I know what I got under the hood

Do you know what's under the hood of the car you buying ??

[yaldizzle]

zerodameaon what you said makes a lot of sense. it could quite possibly be a short somewhere. hopefully ill be able to locate the problem in the wiring too after i replace the ecu with a manual tranny one.
and you guys are right, the motor runs great and it is super clean under the hood. the check engine light scares me cause i live in cali and theyre super strict about that stuff here. so i guys i can go buying and get a smog done somewhere and slowly figure out the problem over time.
i just wanted something all stock so i can do everything myself cause i would know what's done to my car but its hard to find that out here without trying to way over pay for it lol.
anyways, thanks guys