Chevy Silverado and GMC Sierra Forum banner

check engine light flashing while driving in 3rd.

9K views 10 replies 3 participants last post by  SilverSurfer 
#1 ·
I know this has been a real common topic lately hard shift from 1st to 2nd my truck has been doing this for quite a while. earlier I took it to a dealer mechanic and I was told it was the shift relay or im not sure what its called but they reset it for $400. it somewhat fixed it but then it stared up again a half a year later. its become a nuisance. BUT that isn't my question. ive looked at many posts on here and it seems like there really is no answer other than its normal for chevy transmissions.
my problem now is that three times no while driving in 3rd over 55 mph my check engine light starts flashing. nothing else happens but as soon as I put it in D it stops. ive took it to a transmission shop and get nowhere because apparently they cant tell anything if the light isn't on. I have made myself believe that it may have something to do with the hard upshift. but im not a mechanic and I just don't know. "real" mechanics just tell me to replace it ($2500)!!!!!!!!!
Can anybody give me any good news or any suggestions?
 
#2 ·
A flashing check engine light is normally an indication of a major misfire condition. Someone who checks the computer with a diagnostic scanner (not just a code reader) can see if there is a history of missfires and what cylinder it is happening on.
 
#9 ·
There is a TSB out on the harsh 1-2 shift. It calls for installing the 1-2 accumulator valve conversion kit. I just did this on mine and it shifts great now. That TSB came out in 2011.

You said the ck eng light flashes. Could it be some other light? Trans warning light telling you to upshift? Why didn't the mechanic plug in a scanner and test drive it to duplicate the condition? I'd say you haven't found a "real" mechanic, yet.
 
#10 ·
the check engine light only comes on when im on 3rd and im pretty sure its that light, there is no other light for check engine other than on the digital window. I guess it makes sense if its telling me to upshift but I understood its ok to use 3rd as drive. and as for finding a real mechanic, I can agree with that. no one has tried duplicating it.

also for the 1-2 accumulator valve conversion kit. where can I get it and can I install it?
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top