chevylvr

I'm having a problem with my 2002 Silverado 5.3 with 120000 miles now.It all started like 1 year ago i started feeling like the transmission was downshifting between 35 to 50 mph range then one time the trany didn't shift to 4th gear,i got out of the fwy,i stopped the motor and when i turn it back on the light came on but it was shifting into 4th and it remained good so far but it still downshifts so we plugged on the sccaner and it gave us a p0300 code random/misfire,we checked the fuel pressure and it was kinda low so we replaced the pump,after that it seemed to run fine but after a couple of months same problem again,took it to the dealer same code they didn't find out why they wanted to replace my whole fuel system wich was like 2500 dlls and i didn't do it.I've tried everithing fuel filter,pcv valve,clean up mass sensor,trottle,spark plugs,wires,fuel system cleaneall the simple things that i know how to do so if anibody has had the same problem please help me out.Thanks.

BBBTHATROCKS

I had the exact same engine code on my 2000 6.0 liter take it to the dealer. I did after doing anything possible to fix it myself. What they did is reprogramed the pcm and relearned the crankshaft position sensor. It worked great and I wish I would have done it early becuase I did everything you have tried. It cost about $225.00 to get it done, that's what my dealer charged me.

good luck

chevylvr

thanks i'm gonna take it to the dealer and i'm gonna tell them to check on that and then i'll get back,because there is also another little problem maybe it's because of the same thing but sometimes i feel like the tranny or the rear end slips, i don't know what's wrong.

BBBTHATROCKS

Have them check the tranny codes that's were the problem will show up. Once they fix that you should have any more problems. My truck would actually shift out of overdrive anytime I go over 65 mph good luck with it