Strange check engine light problem
 

been having a weird problem with my check engine light coming on with my 93 Chevy 1500.
it only comes on when i hit speeds of 55 and over.at first i was able to stop it by putting on the ac but lately that's not even working.when i had it hooked up to the diagnostic it pulled out 2 codes tranny running hot and cat problem. change the Tran filter and it had a ton of **** in the pan,i also hollowed out my catalytic converter and changed the exhaust it is running alot better but that light is still poppin on when i hit 55 every time.
although the truck is running fine the light just drives me nuts,any ideas on what the problem could be??http://www.truckforum.org/forums/ima...s/confused.gif

I'd try installing a new gas cap to rule out this possibility, it has worked for me before.

check your trans oil, you are probly low, if your transmission is getting too hot that check engine light will come on, you might want to take it in and get looked at, transmission is somethin you do not want to try to do yourself without proper tools.

Hi chevy71,

How are you doing this weekend?

Are you sure your cooling system is working properly? Doesn't make sense your tranny and exhaust are hot, but your engine is running cool.

My first move would be to replace the radiator cap, if it's over three years old.

yeah those are all good ideas but i just changed the radiator,changed the tranny/fuel filter and recently got a locking gas cap.the truck runs at normal temp. about 180 and other then check eng. light popping on,it runs great . I'm just totally baffled.oh and i removed the cat completely yesterday and its still doing it????