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'78 K20 - RootBreaker from 1990 - nov 2025 8.1L not runnin

Confused What The GIF by Sesame Street


I'm confused
 
hp tuners worked to read codes.. they maybe old ones...

Screenshot_20240728_201934_TDN.jpg



live data works.. this pic taken from laptop..didnt realize screenshot captured in it lol

20240728_220517.jpg


but wont read my ecu?!?!??!??!

20240728_211149.jpg
 
ok just read the first P error is issue with check engine light.. uhh yeah i dont have one so makes sense.

Other 2 are related to ECU not getting signal from alternator. Was told if truck is starting and charging, dont worry... and in tune, disable those codes from showing. Well that is great, once I get in there!!!!
 
Reading is the easy part. I've only had trouble on writing, but it should be easy in an old truck with nothing but the PCM on the bus. Did you try low speed?
 
ok so now I can read and got it...sweet..

here is the logging. Once closed Loop happens, stumbles and all kinds of issues...

 
ok so now I can read and got it...sweet..

here is the logging. Once closed Loop happens, stumbles and all kinds of issues...

Couple glaring problems. your control module voltage is fluctuating between 10-12 volts. It should be 13.2+ I think your alternator isn't charging, your battery is bad, or you have some questionable connections or all 3.

Next thing is when you rev it, it goes into knock retard and is pulling timing. That's the stumble you're getting.

Next your fuel trims could use some work. Although not absolutely terrible.

Is this a factory tune? What mods bolt on or otherwise do you have? A noisy or rattling exhaust can cause false knock retard in some cases.
 
Now truck is back to the point before the fire happened...

open loop truck runs great...closed loop and bucks, kicks, etc.

for those that have done the swap..
I used this pedal from parts geek
2002 Silverado diesel gas pedal - 3705-02395358- car-parts.com $60


Had this on page 24 but no part number and cant find in old orders.... it is 10 wires straight though cable. didnt modify at all..

in hptuners i dont know what to look at to log or change...
Drive By Wire pedal to TCM cable

hoping @Larry or someone that has done the swap can assist...
 
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