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pcm or ecm trouble on 98 6.5l 3500hd

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dakota89

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new-brunswick
ok so here is my strory it s a tow truck 98 3500hd 6.5l turbo truck was ruuning fine went to a call for boosting a car a body was with me he toutch the booster cable together while the were hook to my towing evrithing was fine even after that made another towing but the next morning the truck start but idle rough and cant gave him gas it would stall so took it to a garage code reader was saying fuel pump timing and 2 other code that i cant remember but they were reletated to the fuel pump so he change the pmd same thing he try a couple thing and then i dont know why he had a computer there the one under the dash he put it in and the truck has lots of power but check engine light was on he told me because mine was manual and his was auto so i went to the dealer(GM they say they canaot reprogram well the mechanic told me that he didnt know these truck he was a young mechanic so i ask them how much for a new one he told me 310$ but it s comming virgin so i ask them can you program it for my truck haha he said so no luck at the dealer so you sugest what ho yeah i had the high idle mod for sure cause it s a towing but with the pcm he did install the high idle dont work i did follow the wire and the procedure on this site evrything is hook up right but no high idle please help help i can live with the check engine which i dont like but a tow truck without high idle is kind of usless.
 
ho yeah for the high idle the way it is set is b7 and b8 hook together on the same side of a switch and the other side of the switch ground to cab so i m assuming it must be set to 1600 rpm
 
Never let anyone short the jumper cables to see if they spark or are hooked up. You likely also blew some of all of the diodes in your alternator from that stunt as well as the PCM.
 
when i do hook up my old pcm the truck work like crap but if i flip the switch for the high idle it s trying to you notice a change in the idle but will just work like an old car that is flood
 
That is a 4.63 ratio, not sure if my ECM would work. Mine is out of a C&C 3500 with 5 speed and 4.10 ratio.

Maybe someone who knows better can tell us for sure. The VSSB (VEHICLE SPEED SENSOR BUFFER) can be adjusted to compensate for gearing changes
 
Post the code on your ECM,..I have a 98 ECM out of a 2500 HD with AT ,i don't know the gearing but it ain't 410.
It don't have a tune in it though
 
Simon, his has a manual trans, he already has another ecm tuned for an auto trans and that is the problem.
 
thanks guy trying to help me out so do you think i can buy one at an auto parts and they can program it with my serial number
 
a guy told me that napa sell those but i m scared to buy one if you bought it it s your working or not thats what he told me
 
i didnt know it was that complicated cause in my jeep i did blew one in the mud just went to the junk yard grab one install and never had a problem i guess those 6.5 are more complicated
 
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