Bad computer?

[slowhawk]

Got a weird problem.
01 truck tuned in SD 2 bar. Truck runs fine for 30 or so miles then truck goes into a limp mode. There is no codes other than the MAF which is there all the time.You can not reset the computer to get it out of limp mode.The computer needs to be reflashed(partial with EFI live) and runs perfect again for another 30-40 miles and goes out again.After it goes into limp mode the battery light will go on/off but the voltage stays at a steady 14volts.

Anybody have this problem? I'm thinking the computer is junk.

Also the truck has a new battery and altinator. When we got the truck the altinator was burn't up from a loose power wire which melted back a bit.

Thanks
Don

[Doc]

Hi Don,
I take it that the repairs were made to the wire and alternator and you have swapped the pcm with another and the problem has gone away? Any speculation on the melt down in the first place? Big Bon Jovi stereo or something else>? With such a catstrashope as this the well being of the pcm sure does seem to be in question. Tough call to swap another pcm unless you are certain of the repair and underlying cause of the event in the first place.

[slowhawk]

Hi Don,
I take it that the repairs were made to the wire and alternator and you have swapped the pcm with another and the problem has gone away? Any speculation on the melt down in the first place? Big Bon Jovi stereo or something else>? With such a catstrashope as this the well being of the pcm sure does seem to be in question. Tough call to swap another pcm unless you are certain of the repair and underlying cause of the event in the first place.

The wire's melted from shody work from another shop.The main power wire wasn't tight which caused a resistance and melted down the wire while blowing the circuit board in the altinator.The alt. was replaced but the PCM wasn't.

We repaired the wires and everything the other shop screwed up(over 50hrs) and drove the truck alot but probly not over 20miles at a time.Now,the customer picked it up and it went into limp mode once -I drove there and found a reflash fixed it,Then he drove another 30-40 miles and the truck went into limp mode again.

[Doc]

Considering the shoddy work you have already witnessed have you taken the pcm connectors off and looked at the pcm's pins to see if any are pushed in/not seating all the way?

[slowhawk]

Considering the shoddy work you have already witnessed have you taken the pcm connectors off and looked at the pcm's pins to see if any are pushed in/not seating all the way?

Of course we did. I don't see a pin causing this.Runs great,turns to crap,clearing codes doesn't work,but you do a reflash and everything is great for 2 weeks of 20 miles trips then only 30miles,reflash -good for another 30 miles.????

This truck is over 100 miles from us now. I'm hoping someone has run into this before and found the exact problem so I only have to drive there once;)

[Biggsy]

I have seen a similar problem in a non ls1 vehicle (vs commodore), PCM would go into limp mode, disconnecting battery and reconnecting would not fix the limp fault.
Change the PCM and it would work again. Car would drive fine for a couple of days then the same problem would happen again. Change PCM back to the original, and off the car would go again.
No fault codes were activated.

The car originally had suffered from an electrical loom fire. Loom had been replaced but this problem occurred with limp mode.

Eventually the problem was found, it was caused by a short in the engine loom (the new/secondhand replaced one:bash: ).

Not saying this is your problem , but a possibility.

Dave

[slowhawk]

Thanks Biggsy. That is a possibility.

[ace68]

I would look around the loom that gose to the radio because that truck had an electrical problem from a radio install that went bad. Problably melted something aroung that area.

[slowhawk]

:wave: This is just awesome

Got the truck back.Reflashed the computer and runs great.

Get this, the altinator light flicks on/off every once in awhile(the voltage is steady at 14v) and the friggin timing goes up slowly by itself:master:
So,I leave the shop and timing is at 32 degree's at light throttle and 16 degree's at WOT. 30 miles later part throttle is at 54degree's and WOT is a 26 degree's:rockon: The KR sensors verify this by pulling timing when they can.---AWESOME.

So,before the altinator light would flick and the truck would go into limp mode by going to min. timing at load, now it adds timing slowly. Getting a new computer in a few days.

This is just :muahaha:

[joecar]

Before you install a new PCM, try to ohm out all pins in connector for shorts to power or ground or other pins... I know it's very tedious and laborious (I've spent a various Saturday afternoons in my former life doing this), but it may save you from blowing the new PCM.

[slowhawk]

Before you install a new PCM, try to ohm out all pins in connector for shorts to power or ground or other pins... I know it's very tedious and laborious (I've spent a various Saturday afternoons in my former life doing this), but it may save you from blowing the new PCM.

Sure,bring a man down:bawl:

I planned on going over the pins. When we recieved this truck from the "other" shop alot of wires were melting which we replaced and the altinator(which was new) was fried from a loose main power wire-which took out the internal board. So I'm hoping the comp. has just been bad from these event's.

[69camaro5speed]

i had a 2000 truck with the alt. light coming on i was trying to flash a differant operating system in to do a custom operating system because the stock operating system was not listed it being a 2000 truck i was trying some 2001 operating systems the 2 differant ones i tryed made the alt.light came on allso so i flashed the stock one back i ran out of time.was it a custom operating system you where using

[joecar]

Sure,bring a man down:bawl:

I planned on going over the pins. When we recieved this truck from the "other" shop alot of wires were melting which we replaced and the altinator(which was new) was fried from a loose main power wire-which took out the internal board. So I'm hoping the comp. has just been bad from these event's.Sorry mate, didn't mean to bring you down... I'm just being cautious, I've fried my share of electronics throughout my life :doh: (and I'm an EE, so I should know better... :muahaha: )...

I've seen a PCM fail due to arcing of the battery/alternator wire, so that could well be it.

Let us know how you go,
Cheers
Joe
:cheers:

[slowhawk]

Sorry mate, didn't mean to bring you down... I'm just being cautious, I've fried my share of electronics throughout my life :doh: (and I'm an EE, so I should know better... :muahaha: )...

I've seen a PCM fail due to arcing of the battery/alternator wire, so that could well be it.

Let us know how you go,
Cheers
Joe
:cheers:

Hopefully good. This truck is a blast when it's running good.Made 700rwhp and is funny as hell hanging the rear out on a 2500 extended cab setup.

This is a custom OS but it did it off the original file too before OS.

[Big Kahuna]

What a bizarre gremlin. Be sure to post up the cause/fix when you do get it sorted.
700hp sound like some good fun so good luck with it.

[Biggsy]

I'm an EE........
:bash:

;)

[joecar]

:bash:

;)Yes, and I can even calculate when something should fry, and sure enough my calculations are correct... :muahaha:

[DanaliHD]

the truck is mine. it's a 2002. the thing was awesome for about 30min as stated before.

so here's a bump for more help.

[Doc]

Bummer man,

Melted wires, bad alt, unregulated voltage, ...I just reread the post. Ever change out the pcm? The board that was described as fried on the alt provided regulated voltage output and with it not working would cause bad juju on the pcm's mainboard. It seems as though the really tough thing in this case would be pulling the harness for a thorough inspection with it somewhat working for a drive cycle or so after the repairs that have already been made. Considering the extreme things this truck has gone thru maybe it is warranted. Sounds like a really cool truck. I am sure Don, et all will get it up.