Truck pedal P2122 P2127 codes????

[got4lotx]

Looking for some direction here....First LS swap (2012 gen 4 5.3 w/ 6L80) into a 70 C10 pickup. First time using Hp tuners as well. Been a huge learning curve!!!

I modified the stock harness using the LT1Swap.com instructions. I'm using the factory truck DBW pedal. Truck starts and engine will rev when throttle is pressed. ECM is throwing P2122 & P2127 DTC codes. If I clear the codes the TPS will read in the VCM scanner tool but only ~30% to 85%. Once I start the engine the DTC codes come in and the TPS won't read, but engine will still rev when pedal is pressed. I checked a few parameter in Vcm suite with codes cleared and key on but engine off....see below.

Any input on what to troubleshoot next would be appreciated. I double checked the wires from the PCM to the pedal are the correct ones for a factory truck pedal. I can post screenshots of other parameters if that would help. Just let me know what I need to add to help troubleshoot. Thanks!

not pressed Pedal Pressed fully
Accelerator Pedal Position 1 0.94v 4.18v
Accelerator Pedal Position 2 0.45v 2.08v
Throttle Postion (SAE) 30% 83.9%

[GHuggins]

Both of those are low voltage codes. Is the harness wired for a car by chance? I assume so if for a LT1. Pretty sure those voltages should go the opposite of one another. If the harness is for a car that would explain everything as there are two pins that have to be swapped for a truck. I don't remember which pins they are but should make the two center wires the same. I think it's pins 4 and 6. It swaps the 5v and ground for the one sensor...

[got4lotx]

I was told the harness and pedal are both from truck motor. I've been doing some more research...being they are low reference codes I'm going to double check the grounding circuits. Heads to block, block to frame etc. If that doesn't clear them I'll try switching the low reference and 5v reference pins on the pedal harness.

[edcmat-l1]

Why don't you pull a wiring diagram for the donor vehicle? Why would you use LT1swap.com to swap and LS engine?

[got4lotx]

That site has diagrams for several year LS motors. I used the pin out for gen4 LS trucks.

[edcmat-l1]

That site has diagrams for several year LS motors. I used the pin out for gen4 LS trucks.

If your engine, harness and PCM all came from the same vehicle, I'd go to alldata.com and buy a month subscription for that vehicle and use their wiring diagrams.

[gtstorey]

At first glance it doesn't look like LT1Swap.cpm covers 2012 trucks, just 2008.

[got4lotx]

there is a gen 4 truck pinout on his site for 2009 and up, the pin out is the same, I verified using a 2012 Silverado truck schematic from gm. I?m looking for help from anyone that?s had a similar codes after modifying a stock harness. I had to extend the wires, I?m planning to double check the grounds and ground straps. These circuits ground through the pcm, I?m thinking since they are only 5v circuits they are going to required solid grounds.

[edcmat-l1]

there is a gen 4 truck pinout on his site for 2009 and up, the pin out is the same, I verified using a 2012 Silverado truck schematic from gm. I?m looking for help from anyone that?s had a similar codes after modifying a stock harness. I had to extend the wires, I?m planning to double check the grounds and ground straps. These circuits ground through the pcm, I?m thinking since they are only 5v circuits they are going to required solid grounds.

That right there. All bets are off.

Everything needs solid grounds whether 12v or 5v. Since you've tampered with the wiring there's no telling what problem you've caused.

[got4lotx]

Sorry I didn?t by a new harness. If you aren?t going to be helpful then keep quite. I know reusing a stock harness is not as reliable as a new one but I?m trying to save money. Any direction of where to troubleshoot associated with the pedal circuits specific to these codes is helpful. Talking shit about tweaking a harness isn?t.

[edcmat-l1]

Sorry I didn?t by a new harness. If you aren?t going to be helpful then keep quite. I know reusing a stock harness is not as reliable as a new one but I?m trying to save money. Any direction of where to troubleshoot associated with the pedal circuits specific to these codes is helpful. Talking shit about tweaking a harness isn?t.

How is anyone going to be able to tell you how to troubleshoot a harness you boogered up? I was trying to be nice about it.

[GHuggins]

Don't know what phone answering individual they got to do the vid, but should give you an idea as to what I said earlier about the voltages and what not.

https://www.youtube.com/watch?v=nMJ_8tIp8NE

Also make sure since you extended the wires that you soldered the connections and used "like" wire - should be fine stranded small wire for signals. Signal wires and especially ones that "self check" like the accelerator and tps are really sensitive to any connections so absolutely no butt connectors.

Then there's this one that actually shows the voltages and how the difference should always stay the same which yours isn't

https://www.youtube.com/watch?v=HA11RRchHtU

[got4lotx]

Thx. I did use automotive wire and soldered the connections. Similar to what you posted I found this troubleshooting guide:

https://www.obd2-code.com/2018/10/p2...ition.html?m=1

I didn?t have time to do this after work but I?m going to go through and check using this procedure tomorrow. Voltage I saw in the scanner tool and posted above does match what?s expected, I just haven?t checked the plug itself.

One other question?. The codes are showing (permanent) after each code. Could these be old codes, and not currently an issue?

[gtstorey]

On a lot of the GM stuff, the sae pid is not the one to monitor for accelerator and throttle stuff and will give inaccurate values. Check the non sae values.

[GHuggins]

Permanent codes clear once the problem is gone. Might be a good idea to look up diagnostics to your exact vehicle as you can see they change a lot vehicle to vehicle and manufacturer to manufacturer. Your voltages aren't exactly half voltage on the second sensor, so any connection issue will make things a lot worse.

I have seen a lot of weird things that will cause pedal codes even CAN communication lines not hooked up or operating correctly going to a fpcm for instance can intermittently cause them. That's pretty much only on the newer stuff though.