Don't know if it's a coincidence, but recently swapped chips, started right up, idled good. Took it for a spin and within 10 minutes everything went down hill. Engine started to run like crap, pop, bucks etc. Idles horrible. (limp Home Mode?) Check engine light came on instantly, also noticed that right about the same time the speedometer quit working. Checked for codes and all I get 12. Has anyone else run into these symptoms with no trouble codes being stored even though the check engine lights up?

I'm thinking that maybe the ecm took a crap, but speedometer quits at the same time?

 

 

Changed out the chip and the engine is running smooth again, speedometer working without any issues. So far, my explanation for all the issues was the chip. Apparently, bad chips won't necessarily give out trouble codes in the conventional way that we're used to retrieving them. I need to make time to hook it up and make some data logging.