def1

Ok so I'm a long time lurker and have posted maybe once or twice ever lol. Having said that, i have a 95 c1500 with a 7427 pcm that seems to have locked out int and blm updates. Now im not certain of this because i have a spare pcm that is doing the same thing. So a bit of background here....this truck suffered feom massive corrosion issues. I ended up having to replace the distributor, and oddly enough also had to run two new injector control wires from the pcm. I've hears they are soldered into the harness somehow which makes little sense to me, but regardless i ran two fresh wires direct from pcm to injector connectors. I have some minor corrosion in spots at the pins of the pcm and harness but ive cleaned it up as best i can, and remember its acting no different than the other pcm i grabbed for it. My 12v feed to the pcm was apparently shot for a while. When i started my repairs I noticed the pin was broken internally and lightly corroded on the tips. I have also replaced battery cables and alt cable. Anyway i solved that issue so let's safely assume both pcms are in identical shape and functioning. Before the truck broke down from all of those issues along with blown header gaskets, it ran great at and tuning was a breeze. Idled great in open loop after tuning as best i could in closed loop with a bad o2. It idled perfect and all of my blms were 127-129 with most being 128. Now that ive done this rewiring if you will, the int and blm do no move at all. Theyre stuck at 128. I am using the latest tuner pro.

My engine combo is just a stock 5.7 tbi with heavily ported 193 heads, 97 fbody lt1 cam, shorties, tbi mods, Bolt ons. It ran like an absolute beast before it broke down. It shakes and surges at idle. Once it warms up, it mellows out a bit but still isnt smooth as glass and has its rpm dips here and there. Its running rich. I have no codes. Before i forget, i had to run a new map signal wire as well, but that is working properly. I don't think i changed anything in the tune that would lock my int or blms lol.

The bad news is i have just a few days to solve this problem! Also some of my tunes arent working properly if i use an older trusted "safe" tune. Could be a coincidence or just my bad luck. The chip ive had in it for a while ran fine aside from the mentionws issues, but i erased it and burned an older tune onto it that is one of my safe tunes and it wouldn't even start. Then i load my newest tune which is just a slight variation of the one i had been starting with and it fired up super fast but had zero communication with the aldl port yet the ses was on. Couldn't retrieve a code via scanner or jumping the aldl. I put in the stock prom and removed my adapter and socket and the ses goes out and it runs decently smooth, but still no int or blm movement. It restored my aldl communication, but so did using a different tune. Im not sure what the heck is going on here. I have to get this truck running before monday so i can start my new job! Which is a 45 commute so I NEED my truck!

Vanilla Ice

If you can datalog check what the o2 are reporting.

def1

I am in open loop idle and the o2 on my last log from yesterday is staying around 650-850 mv. I know the sensor is toast due to few cross counts when in closed loop.

def1

I wouldn't think a bad o2 would lock me out of int updates. I'm willing to believe it though at this point.

def1

Im watching my log from yesterday and the int and blm finally moved with throttle but it wouldnt donthat today. Still had no movement at idle and it is running pretty rich so clearly im something is wrong. It's 20 mins of idling at temp with no change or wven a blop of an int change.


I will try again in a bit as soon as my laptop charges. I will see if it moves under throttle. Another point worth mentioningnis the speedo needle has been jumping in park with i gove it throttle. Never goes oast about 10-15 mph. I havent tries it today to see if it's still doing it after all these prom changes etc. it doesnt show in my other log so im assuming it's another issue probably to do with rf noise or something, but im willing to hear ideas of what it may be.

def1

So i tried another chip with the last known tune that was really killer before the breakdown. It runs much better, but now im out of gas so that's super. Still no int or blm. I may have actually gone full open loop on this chip, but I should still have int. Nada. Is there a hidden bias somewhere I'm missing? If i repaired all of those issues and it fires up, it should run fine. Theoretically. But it doesnt. This tune is better as i mentioned. I would think I wouldn't get this far if my grounds were bad, so im counting that out. So this time around the blm and int never changed with throttle. This is crazy.

Also, I don't believe the tps ever moved with my extra throttle blip in the latest log i just did, but I don't seem to be having tps symptoms

Maybe a bad data signal wire from the pcm to aldl? But that doesnt explain why it's running like poo