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Thanks for the diagrams. I took the PCM connectors out and verified wiring for the pedal a,b,c,d,e,f to PCM.
Plugged everything back in and the a,b,c,d codes went away. Still don't know why... I only measured some connections. Engine runs even quieter now, must have been running in high idle before.
Gives me the code for d/e voltage relation now. When I first turn on the car the pedal works for a split second before throwing the d/e code. I verified the d/e connections between PCM and pedal. Got 3 ohms on both. Kind of stumped now. I also got a new pedal but it makes no difference.
If you erase the code, does it pop up immediately a few seconds after startup or do you have to hit the accelerator pedal for it to set? Just curious.
Either way, I’d look at both of the APP sensors voltages if your scan tool will let you and see what they’re doing during a full pedal sweep. On our cars, you’ll have one sensor read closer to 5v at rest, and decrease closer to 0v as more throttle is applied, vice versa for the other sensor signal.
We usually get those voltage correlation codes for the accelerator pedal or throttle body if there’s an open circuit in the harness, the wrong part is installed (there’s like four different throttle bodies for 6.2L F250s that all differ in their sensor voltage readings) or a sensor itself has gone out. Sounds like you’ve ruled out the harness as long as there’s no pin fitment issues. APP voltage readings should help narrow that down if you can see them.
22741800 both pedals I have are new OEM GM ones.
The code sets when I hit the pedal.
Thanks for the tip, I'll try that. I have Hptuners and obd link mx or whatever it's called. Hopefully I can see app with one of those.
The engine originally came out of a colorado. I installed Camaro water pump, intake manifold and oil pan to make it like a Camaro. I reused colorado throttle. Do you think that could be the issue?
Also this cbm motorsports harness doesn't utilize the stock oil sensor. I wonder if that could be an issue too?
Z WAAAAAZ and Curly are both professional mechanics, they are definitely giving you great advice. I am not a mechanic, but I have done the LFX swap and had this same problem...so something like sleeping in a Holiday Inn last night.
In my opinion, a throttle pedal not working on an LFX build is super common. I've know/spoke to about 10 people who have done this swap, and you're the fourth that has had this problem. (and that's the people who said something about it. I wouldn't be surprised if a couple more had it and just didn't come up in conversation.) I am one of those people who had the dead pedal, although mine was intermittent, and it took me about 6 months to find the issue. My pedal would work a little bit, putting me in "limp mode" if you will and I'd only be able to go 10 mph fully floored. Most of the time / in the beginning it only happened right when I started up the car, but eventually it started to happen while driving the car. The worst was in the pouring rain, during rush hour on 285 in Atlanta and I came to a stop in the left most lane with no throttle, talk about not making friends. For me, shutting off and restarting the car a couple times would make the car work again.
In the 3 cases including mine, it was a wiring issue from the pedal itself to the ECU. I wouldn't bet the farm, but I would bet the tractor you have a wiring issue. I seriously doubt it's the Chevy wiring harness, throttle body, or the pedal (I swapped the pedal myself hoping it was going to solve my issue). I'd be looking real hard at the wiring harness you bought. (If memory serves you mentioned that it wasn't well built.)
Maybe you have done this, but I'd put the multimeter down and go a little more cave man on the problem first. (and maybe you have done this already) Have you pulled on each and every wire (more specifically those 3 or 2 giving you issues?) at each and every connection? Check that the pins are seated properly in the connectors? Do you have a wire that is crushed or pinched in any way? Any chance you have something pined wrong (like something swapped?)
My issue was at the connector in the engine bay that connected my pedal to the ECU / Chevy wiring harness. "A" was my issue, I didn't have the connector/wiring supported well enough and it was pulling on that wire as it moved around a little bit in the engine bay. (I added that zip tie as a support when I fixed it.) It looked perfect, and you could move the connector around and would have never noticed the wire was loose. But when I tugged on the wire, it pulled out like it was never crimped. (Don't forget to check the other side of the connector too, where the OEM wiring goes, because I bet that is a new crimp too. (I cut off the OEM connector that was there, and re-pinned those wires.)
I know I was told to use good wire and to not use a pigtail with it. (Cause others had the issue, and warned me before I built my harness that the throttle was very sensitive to how you wired it.) I didn't go fancy, I just used 20 gauge TXL, cause that is what the Chevy wire looked like to me, and its working, but I think the other two swapped to a higher grade military wire. Even if all the pulling and checking looks good, if you still have the issue, I would try rewiring D & E and see what that gets you. I know that isn't as good of an answer as pulling out the multimeter and finding the actual source of the problem, but you have already started throwing parts at it. 20 feet of wire and some new pins is a lot cheaper than a new throttle body.
Good Luck...I know this is a pain. I think you are close to solving the issue.
I might be a mechanic but rdb’s input is much more pertinent haha. I was gonna say I thought I’d read about one or more similar issues before with these swaps. Interested to see what OP finds!
Thanks a lot for that write up. Yesterday last 3 times I started the car it would idle great only throw the DE code/no throttle. Today I started it and it sounds like a subaru(runs on 4 or less cylinders), Open a,b,c,d codes are back.
This harness has a 12ft cable for throttle so I cut it down a short as possible for my setup as per rdb138 and reused the connector from the truck. Started the car - idles great no codes other than clutch position, when I tried throttle it worked for two tiny revs and stopped working - DE code again. I then switched to my other pedal to see if it made a difference and the car started like a subaru - open a,b,c,d; I switched back to the other throttle but it still runs like a subaru - open a,b,c,d; i tried several more times with the same result.
I ran out of time today but I will go back and repin and run new lines for the throttle body and the pedal tomorrow. If that doesn't work I think I will try to get a new PCM. It just doesn't make sense how it can go from having connection to having 4 opens without any physical changes.
That’s pretty agitating lol. But based on what you’re saying, could also be connector pin fit issues. I can’t remember, have you taken a look at all the female pins to make sure they’re square and not warped? I had a similar issue with an ignition harness a few weeks ago. Female pin for power to all the coils from the fuse box was warped just enough to not make good contact. Just barely visible enough to see it was different than all the other female pins.
I’d check all of the female pins for square-ness (that’s a word, right?) at the APP and ECU connectors before condemning the PCM, quick work to check that off the list. Were you able see what the APP sensor readings were doing when the car threw the fault codes?
It sounds like the throttle and running on 4 cylinders are separate issues - if the ECU can't read the throttle it should just go into limp mode. Might be two issues going on, both aggravated by vibration when the engine is running. Might be worth checking for continuity from the ECU connector to the throttle while shaking the wiring (put the multimeter in "beep" mode). If that doesn't reveal anything I'd put my money on the harness -> throttle connector. If you wanted to replace that connector here are the part numbers you'd need, the 1x6 pin connector is sort of hard to find:
This is starting to get annoying haha. So I start the car today, runs like champ, 1 code p0807 Clutch position sensor "a" circuit low. touch the throttle, throws DE code.
I rechecked all the connectors, took the PCM connectors apart to make sure all pins seated and square, took backs off the connector to look for kinks in wire etc, everything looks great. I pulled some wired pins out of the truck harness and ran new DE lines to the pedal bypassing the x102 connector. checked with ohm meter 2.6 ohms (used to be 3) progress? lol. Start the car runs good but throttle works only once and throws d/e code.
I left my hptuners laptop at work so I'll try to check app with that this weekend, the obdscan tool I have doesn't have that option.
I'm wondering if p0807 clutch position sensor "a" clutch sensor circuit "a" is the issue. It's the only remaining code.
Also isn't there some kind of a throttle learning procedure? Could that be my issue or no?
Are you sure the pedal connector is wired correctly? Looking at the schematic it's plausible that the problems you're describing could be caused by the wiring being backwards - IE, A and F are reversed, B and E, etc. The whole connector is rotated by 180°. It sounds like B and E (the potentiometer wipers) are reversed, so it works fine when the pedal is at one extreme but they differ when the throttle is pressed.
Edit: The images below should tell you how things should be connected to the ECU and throttle pedal
I have an LFX Rx8 that I put together with the Keisler kit, and this is a video that he sent me after I was having some throttle issues at the track. I think I actually broke a wire in my harness, and was very careful running the replacement harness. Haven't had any issues since.
Any updates on the build? Please share progress if you can. Its an awesome build and I am super curious how the car drives and how much power you are making.
Tldr: didn't like the shifter, went turbo ls 8hp70 instead.
My pedal issue ended up being a bad ECM and pedal, when I swapped ECM, car started no codes. When I tested the pedals with new ECM one of them would throw codes.
Anyway I had it buttoned up and drove it around with charge piping disconnected so I could test the car before getting it tuned on the dyno.
I found the shifter so bad especially 2 to 3(which you do all the time because 1st is useless) that it made it unenjoyable to drive the car. Soo I went back to the drawing board.
I ended up picking up an aluminum 5.3 LS 7875 turbo and a big case 8hp70. It required even more radical firewall and tunnel mods(entire engine still behind the steering rack). So I ended up tube framing the front of the car. It's been super fun building it so far. I'm waiting for a camshaft(got sent a rusty cam twice...) to finish building the engine and then everything can go back in. I'll make a separate thread with some photos as I have a ton of questions regarding rear end/driveshaft and 600+HP/tq
Now that I'm almost finished my ls swap I can share my experience. Lfx swap is almost as expensive as LS swap but it comes with a ton of headaches - parts are hard to find and are a lot more expensive than LS, very limited aftermarket support, certain parts they don't even make anymore. I.e power steering pulley. LS is a lot smaller and has a lot more intake and oil pan options to make it even more compact. If I were to do it again I would start with an LS engine.
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