check engine light still comes on randomly

[90K5]

Every now and then, my check engine light will come on for a few minutes and the nturn off. I replaced the O2 sensor and it still does it. I've got a code scanner and as soon as it comes on, I turn off the truck to get the codes, but can't get any...any ideas?

 

[Chris Demartini]

<font color=blue>The key has to be in the run position to retrive codes

 

[solowookie]

try a big hammer - you can fix anything that way... /forums/images/icons/wink.gif LOL

 

[90K5]

I know how to get the codes...there are directions in the book...the light must get reset when I turn it off.

 

[Blazer_Boy]

Nope, the computer has a memory that will retain those codes when they appear. You have to unhook the battery to erase them. It would have been silly for GM to only have the codes displayable when they are occuring. You have to get through "12" three times before you get to see the problems. A paper clip also works in place of a scanner "tool". Try taking that paper clip and sticking it in the two upper right holes on the diagnostic port. The check engine light will blink your codes. Might as well do it the way GM designed it to work. The far right plug is the ground and the one next to the diagnostic plug. Don't have the truck running when you are checking codes, just the ignition on.

 

[big d]

i had the same problem you had. and got the same advice. mine came on for alittle while at first and then shut off. then it stayed on all the time. when i tried to read the codes nothing came up. truck seemed to run fine. took it to the garage and came to find out it was the throttle control sensor. could be the same problem with yours. worth checking out. btw, this was on my 87' k5.

 

[90K5]

do you mean throttle positioning sensor? Can't find a conttrol sensor...where is the TPS? Also this was strange. Today the light came on under normal driving, but turned off when I accelerated hard...

 

[zcarczar]

Mine is doing that but when i took it into my shop it turns out i knocked an ignition senser off the bottom of the engine, it was something to do with the ESC(electronic spark control) and i plugged it back in and it comes on once and a while but i havent been able to run it with the scanner yet to see what code it is

 

[big d]

yes i believe that is what it is called. it cost 100.00 plus bucks at the shop, but probabley cheaper through local parts dealer. could it be the oxygen sensor, and when you accelerated it sucked more air and shut off ? personaly, id take it somewhere where you can have it put on a computer, diagnosed, and then maybe fix it yourself. well worth the bucks. that throttle position sensor is on the left front (side) of the throttle body. hope this helps, and id get it checked out a.s.a.p. just in case you may have some other problems, hate for you to loose your motor or cause serious more problems that cost $$$$$$$.