pedal suddenly goes limp - no code

[[email protected]]

i don't have any good background on this, whole swap was done by someone else and i'm just another stop by the owner on the way to trying to get it fixed.

the computer comes up an 09, but it also has an 8sp swap with the dial gear change. was the 8sp available in 09? i don't think so. but i mention it because it might be helpful.

what's happening is the pedal suddenly goes limp at highway speeds. even at steady throttle, it will do it. when it happens there's no codes or anything to help troubleshoot.

the vehicle is a 51 dodge truck and owner was told the whole thing came from a single donor, ecu, harness, pedal, engine, trans.

there's no speed in the log which seems unusual. unfortunately i didn't log anything from the trans and truck isn't here currently. this could be the source, i don't know. the dash has a gps driven speedo.

in pedal3 file it happens at 8 seconds. you'll see the spark graph suddenly drop. in pedal5, it's at 1m and 25 seconds. the spark suddenly goes sawtooth.

in all cases the accelerator pedal position sensor goes to zero (which is closed throttle reading too). my first thought is maybe the APP should be replaced, but key off and on and everything is back to normal. and keep it under 65mph doesn't happen.

any help is appreciated before we start throwing parts at it.

[f.creek-ranch]

Thats something for a fortune teller...maybe its cheaper

seems like a cut.

Disable all torque management from tranny and esp.

maybe you can play around with transmission settings. A580 is equipped, try manual tranny. maybe it doesnt communicate and is a stand alone one.

[[email protected]]

if you re-read you see i said it's an 8sp. i know it says 580 yes in the trans tab, but you'll also see there's no tables there.
it appears to be an older ecu with the separate 8sp tcu, swap. didn't read the trans because in the past never had to do any trans torque mgmt in 8sp originally equipped cars.
this is the first 8sp swap i've seen. didn't know it had been cracked but here it is so....
was hoping to catch someone here knows newer swaps and what it takes to get it done right.
fingers still crossed.

[GHuggins]

I can see where one pedal dtc is set to no error. You might want to compare to an OE file and start from there. I'de also say if you have an 8sp there's probably a better chance of you having a truck engine/trans combo or a wrecked cars. You might even want to run some component part numbers to see if everything "should" work together. Going in behind these idiot shops that tell customers - oh yes, this will work and is the best way to go - then 2 yrs later you wind up with it is always fun and usually requires redoing a lot..

[[email protected]]

ok. i didn't even look at ecu/tcu, not to mention get part numbers and see what years they're for. nor did i look at dtcs, that's a good call. what i think it is an MT engine file and then i don't know on the tcu side, but bigger problem is i've not seen an 8sp yet and not read anything as what you need to get it done right.
i think we're going to try a pedal and see if it makes any difference.

[2knight]

Mine did the same thing. I could drive forever in town but highway speeds it would just go to idle until powered off. Drive for a bit and it would keep doing this. Turned out you need to have a couple brake signals going to the ecm. The newer trucks have 6 pin brake switches. I didnt want to swap my brake switch so i added 2 relays for the computer inputs and problem solved.

[[email protected]]

that's HUGE info. do you know what inputs are needed? this would so helpful.