LS1TECH - Camaro and Firebird Forum Discussion - Conversions & Swaps

Weird throttle pedal and throttle body behavior

FishyZ28 — Sun, 19 Apr 2026 12:53:16 GMT

Hey everyone. So this issue has me ripping my hair out right now as well as giving me a massive headache trying to figure out what's going on.

Has anyone here ever experienced a throttle body that opens and closes just fine with pedal movement while the engine is off, but completely ignores pedal position when the engine is running? VCM scanner with engine off shows pedal position and TPS percentage both moving in relation to each other (though pedal position goes to 160% at WOT for some reason). Yet when the engine is idling, the TPS stays at its idle position even as the pedal position percentage is shown moving with pedal actuation. On first start, I have no codes and it idles perfectly but completely ignores pedal movement. But if I shut the engine off and restart, it struggles to idle for a few seconds then stalls and throws a P2135. If I clear the code and restart, it idles fine once again but still without throttle response, shut down, restart, stalls, sets code, etc...

Yet through all of that, if I move the pedal between restarts the TB blade moves just fine. It's only ignored and doesn't command the TB with the engine running.

This is a swap project with an LQ4 out of a 2003 Yukon XL Denali. I've got a PCM out of a 2006 Silverado 2500 HD with OS 12587811. And a matched pedal and TAC from a 2006 Silverado 1500. TB is the stock unit from the Yukon but all my research shows this TB was shared across all DBW 5.3s and 6.0s from 2003 to 2006 so this should work with the 2006 components correct? If I try to go buy a TB online for a 2006 2500 HD, the part number is exactly the same as what I currently have installed.

I have checked the 5v reference and low ref pins going to the pedal from the TAC with ignition on and those are good. Motor voltage at the TB connector is good when first turning the ignition on. TPS 5v and low ref at the TB connector is good. Motor windings in the TB checked ok at 3.2 ohms pin to pin. I have no idea what kind of resistance the TPS sensors on the TB are supposed to be at so don't have measurements for those.

I hooked the pedal up to a 5v supply and watched the voltage readings. Completely off of the pedal, the voltage for APP 1 is 0.93v and at WOT it's 3.99v. APP 2 was at 0.93v off the pedal, and 4.25v at WOT. From what I found online, these readings are a little high. Especially APP 2 at WOT. The test i found stated it was supposed to be a set 4v at WOT and I'm 0.25v higher. I have no clue if this will cause my issue though.

I'm just hoping someone can chime in here and let me know what they think could be going on. I would like to avoid a parts cannon mentality if possible. I'm leaning toward a bad TAC module right now but I just don't understand how it commands the TB fine with the engine off but loses all command of it with engine running while inconsistently setting a P2135.

Any insight here would be greatly appreciated! HPT VCM Scanner log of pedal vs TPS command with a restart and stall attached for your viewing pleasure.

Thanks all!

P.s. for clarity;
I didn't have this command issue with the engine's original PCM and TAC with a pedal from a 2004 Silverado. But I was struggling with issues of the TB going WOT at 60% pedal position which made it a chore to drive due to pedal sensitivity. I killed that PCM due to a short from a cut wire I hadn't noticed so figured in hopes of curing the sensitive throttle issue, I would just swap everything but the TB out for '06 parts since the '06 plastic pedal fits in my swap better anyway. Unfortunately, this plan has gone sideways as stated above. When swapping the PCMs, I decided to keep the '06 OS and just copy over all the calibration changes from the tune I was running on the original PCM. Nothing in the electronic throttle area was changed though. I kept all of those settings just how they were from factory for the '06 PCM in hopes of keeping perfect calibration between the PCM, TAC, and pedal now that they were all matched unlike before.

Attached Files

2006 pcm throttle pedal issues.hpl (107.8 KB)

63 impala LS build

eth727 — Sat, 18 Apr 2026 16:48:45 GMT

Hey guys I pulled the trigger and bought a 5.3 with 4l60e. I need help on getting the exhaust manifold. Which ones will fit a 63 impala?

2011 Denali 6.2/6l80 into 2007 avalanche

bufmatmuslepants — Thu, 16 Apr 2026 00:17:19 GMT

I have the opportunity to buy a 2011 6.2, 6l80 and AWD transfer case from a Denali and it comes with the entire engine harness and ECM, the TCM is internal to the 6l80. I want to put them in my 07 avalanche 4wd which currently has an 5.3 4l60 but I want to keep a 4hi/4lo transfer case. I know I�ll need a 6l80 autotrac transfer case for the spline count, but the AWD case is just a dumb case with no electronics so I�m struggling with how to integrate this.

Do I use the 2007 ECM, and have it flashed for the 6.2 and 6l80 with a mail order tune, or do I use the 2011 ECM and have it flashed somehow to know it�s got a real transfer case now? Do I need to use the 2007 harness since it has the transfer case wiring or is that separate from the engine harness? What about all the VINs in the ECM, TCM, guage cluster, BCM, all that stuff? HP tuners? Do I need a shift stalk with the manual mode buttons and a new 09+ cluster to see the gears?

Has anyone ever done this before? And no I don�t just want to sell my truck and buy a 5.3 6l80 avalanche and just swap the 6.2 and do a lift again. The trans seems to be the biggest issue, and I don�t (yet) want to do a 10 speed conversion as that�s another $5000 with the conversion harness.

any hints on what I need? Where to start? Don�t do it?

LY6 and 4l80e question

Sinister81Z28 — Tue, 14 Apr 2026 22:33:04 GMT

I have a built LY6 engine that I�m getting ready to install in my project.

I also have a built 4l80e trans with billet converter. I bought a TCI Flexplate part number 399754. The flexplate comes with an extension/adapter for the crank. Do I need to use this extension/adapter or is that for older transmissions and or dished flexplates?

1996 Jeep XJ LM7/4l60e Swap

speeding_infraction — Tue, 14 Apr 2026 13:53:06 GMT

Hello all, new member to the forum. Been around jeeps for about 5 years since I got my first vehicle, a 1989 Jeep Comanche. Just picked up a 90% finished LS Swapped 1996 XJ. It needs a lot of little things to be a good daily, which is my goal. Going to have lots of questions and hope you guys can help me out.

Specs:

5.3/4l60e out of a 2002 Tahoe
0411 Computer out of a 2002 GMC Yukon I think
NP261 Transfer case
everything else is stock except for an external booster pump

I'm not planning on sticking with the 4l60e/261 combo for good. my two options I'm considering are a 4l80 or AX-15 (end goal is to have a 231/242 t case to get the speedo working). AX-15 would be a lot more fun but I do want this to be a good daily and I don't want to have to drive a stick all the time. Currently doing that with my truck and it does get annoying.

Trans is currently in limp mode, I pulled these codes off the other day. P0758

P1860

P0785

P0753

P0740

P0650

P0178

The wiring is horrible. Their version of a splice was twisting the wires together and then putting electrical tape on it. I'm rewiring the fan harness, and likely a bunch of other wiring I found that I have no clue what it's for.
You can see some photos in my introduction thread.

https://ls1tech.com/forums/introduct...j-ls-swap.html

1996 Jeep XJ LM7 Swap

speeding_infraction — Mon, 13 Apr 2026 14:27:24 GMT

5.3/4l60e out of a 2002 Tahoe
0411 Computer out of a 2002 GMC Sierra 1500
NP261LD Transfer case
everything else is stock except for an external booster pump

I'm not planning on sticking with the 4l60e/261 combo for good. my two options I'm considering are a 4l80 or AX-15 (jeep 5 speed) (end goal is to have a jeep 231/242 t case to get the speedo working). AX-15 would be a lot more fun but I do want this to be a good daily and I don't want to have to drive a stick all the time. Currently doing that with my truck and it does get annoying.

I overheated it yesterday at Cars n Coffee, the fan power wire broke off and it finally started running like crap and shut off. hardwired the fans to the battery and it cooled off fast but don't want that to happen again.

Russell fittings

J McGraw — Fri, 10 Apr 2026 23:15:37 GMT

Has anyone had issues with Russell fittings lately? I am building a 72 C10 right now and used Russell adapter fittings to convert the Saginaw rack's 16 and 18 mm o-ring connections to 6AN. The high pressure fitting leaked like the o-ring was missing, so I pulled it apart and the o-ring was intact, so I replaced the o-ring and put it back together again. After starting back up, it proceeded to dump another quart of fluid on the floor! After pulling it back apart again and seeing nothing wrong, I started measuring the fittings and the rack that it screwed into. I found that the adapter was bottoming out against the rack on the hex of the adapter before the adapter was compressing the o-ring. It was the same on both the high and low pressure fitting, but the high was the only one leaking because of the high pressure. I had already pissed away a couple of days on this issue, including trying to contact Russell (which was an effort in futility), so I just went on Amazon and bought 3 different fitting sets that were available to ship today. I figured that if all 3 sets were the same as the Russell fittings, I could just send them back. Well, the fittings showed up and all 3 sets were 1/16 to 1/8 inch longer from bottom of the hex to the seat of the o-ring! Keep in mind that all 3 sets were cheap, offshore made adapters, as the name brand stuff like Earls and like were several days out before delivery. Put one on the offshore adapter sets in and the when torqued up, there was a good gap between the hex and the rack body like there should be. The cheap adapter properly compressed the o-ring and Russell did not. Filled it back up and the system is dry as a bone with no leaks! For almost 40 years, Russell has been my go-to supplier for all performance plumbing, but because of poor customer service and even worse quality control, I am rethinking my position. I was always willing to pay a premium for top quality and good service, but with the new ownership of the company, I just don't think that they are as good as they used to be. I have been building cars for over 50 years, and I have never seen customer service as bad as it is today. The notable exception is Summit Racing as they have never failed to resolve an issue quickly and properly. I actually bought these fittings from Summit, but just did not feel right bitching at them about the quality since it was outside of their control. I am sure that they would have refunded the sale, but I bought these fittings over 7 months ago just to have in stock on the shelf and did not feel right about trying to get a refund on them.

Regards, John McGraw

Gen 3 pedal with gen 4 throttle body using Haltech

Sixtwo — Fri, 03 Apr 2026 13:46:53 GMT

I have an 02 lq9 engine, pedal and tac going in my 72 nova. I also have a gen 4 intake and dbw throttle body to all be controlled by a Haltech rebel ls. Trying to get confirmation if I can use the gen 3 Escalade pedal or if I need to upgrade to the Corvette style. I haven't laid out my harness yet ,as I'm not to that point ,to see what the connections look like but haltech seems to think it will work without a problem. Asking here because in all honesty the tech didn't seem too sure of his answer or perhaps I wasn't explaining the setup as well as I should have. First swap so I'm still learning as well.

1976 Porsche 914, LS3, E38 ECU and 997 Pedal. LIMP MODE

Gearup — Fri, 03 Apr 2026 09:47:11 GMT

Good afternoon,
I have a recently swapped Porsche 914 with an LS3 crate motor, paired with a Chevy E 38 ECU and a Porsche 997 Pedal. The car ran well for about 1000 miles and now it keeps going into limp mode and keeps triggering a P2138 code. Has anyone in here had issues with Pedal correlation between another manufacturers Pedal and the E 38 ECU? I�ve done a fair amount of research but hoping that somebody might have figured this out.

64 nova to 2016 camar

452BIGpine — Tue, 31 Mar 2026 21:51:37 GMT

i bought a 2016 camaro ss with 4000 miles wreck i put the fire wall and dash in the nova using the original wire harness need help on the wiring any help thanks tommy

LQ9 new build running hot at idle

NCDEERE — Fri, 27 Mar 2026 14:45:19 GMT

New build in a 72 C10. Engine was refreshed with all new gaskets. 6.0 LQ9 with 243 heads. Summit 8714-1 cam, long tubes and a TBSS intake. Volvo XC90 PWM fan running wide open for now through a Champion three row radiator. 160-degree Motorad stat brand new. Drive by wire using Terminator X Max. Its running on the initial set up as the truck is largely apart for body work. So, upon start up the engine quickly climbs to fan temp at 190 in about three minutes, the fan comes on and the temp continues to climb until I shut it down. It's been up to 220. I'm new at the term X but the idle timing seems low, its idling between 9 and 12 degrees. Also, the heater hoses are running through the heater so no stoppage there.

PCM not commanding TCC lockup

paradigmGT — Thu, 26 Mar 2026 22:23:40 GMT

My green / blue gen 3 PCM is not commanding TCC lockup on my 4L80e. Car isn't throwing any codes, it isn't misfiring. I turned off DTCs for EVAP and rear o2 sensors.
I am able to trigger the PWM TCC solenoid as well as other solenoids both manually providing ground and power at the correct pins on the trans harness, as well as through an Autel scan tool from OBDII port.
I segment swapped the transmission diagnostic and calibration tunes 4L80e tune from another 2007 express 3500 van with 4L80 using Universal Patcher, and still no changed. I ran a filter for TCC comparing both my bin and the express van bin. The only thing that I saw that I am not sure applies to the 4L80 is that the TCC_Enable_Solenoid_Present is not checked, however I believe the 4L80 doesn't have this solenoid and only the PWM solenoid for TCC, or are they one in the same and this should be checked?

Is there anything else I should be looking at in the tune to get the computer to command TCC lockup?

5.3 with 4l80e in lt1 93 - transmission mounting help

5.3-93fbody — Wed, 25 Mar 2026 16:32:17 GMT

My question is, are the mounting holes for the transmission crossmember (on the chassis) in the same location for an automatic between 93-97 and 98-02?

I�m looking to use this part:
https://bmrsuspension.com/product/336

but I�ve done research and can�t find out definitively whether or not the mounting holes will line up. Some forums say yes, some say no, but no proven answer. Any help is greatly appreciated.

1952 Fiat Topolino

Scott Danforth — Mon, 23 Mar 2026 11:58:58 GMT

May as well start a swap thread here so people know what I am working on. This build is on hotrodders as it really isnt HAMB friendly. link here. https://www.hotrodders.com/threads/1...roject.550685/

A few of the LS1 threads over the past few years as I am actually engineering most of the kinks out of the build prior to cutting and fitting
https://ls1tech.com/forums/generatio...endations.html
https://ls1tech.com/forums/carburete...-ignition.html
https://ls1tech.com/forums/generatio...tic-trays.html
https://ls1tech.com/forums/conversio...p-headers.html
https://ls1tech.com/forums/conversio...on-needed.html
https://ls1tech.com/forums/conversio...on-needed.html
https://ls1tech.com/forums/conversio...e-oil-pan.html

the vehicle is a 1952 Fiat Topolino Belvedere (wood sided wagon). originally born with a 35 cubic inch 16hp motor and a 4-speed transmission...... Its got 3 doors, 4 seats, a retractable soft top and will have a target weight between 2000 and 2200# with as close to a 50/50 weight distribution that I can get. currently the calcs are 50.5 front, 49.5 rear.

The car total length is just shy of 11 feet, and yes, I know that many altereds started life as early fiats and were stretched to fit a V8. this will remain the same length it left the factory, maybe even shorter as the bumpers were removed and I will be fitting a nerf bar style bumperettes.. that is shorter than 4 seater golf carts and literally the same length and currently the same width as an MG midget. currently its just a tick over 50" wide. and 54" tall.

current wheel base is 78", way too short, so that is getting stretched. rear axle is moving backwards, front axle is moving forward. the final wheel base will be between 88 and 90"

to literally fit the width of the transmission and the seats and keep the car a manual, which means the footwells need to go from what is now only 9" wide with the bellhousing and transmission to a minimum of 12"........ it needs to be widened. That is splitting the car down the middle and adding 6+ inches of width. because the proportions are wrong as it sits, and its taller than my daily whip, It will get a mild chop along with having the fenders widened 5-8" on each side

Since I could not find a 3D model of the 500C, I am currently using a model of the 500B - same dimensions, different grill and facia. I will be modeling the complete vehicle including the body sectioning while I am sourcing parts, validating fitment in 3D prior to validating in 2D. in the past I must have hoisted engines and transmissions into a chassis no less than 20 times per build. This build will be planned down to a complete model of the frame, cooling system, HVAC, etc.

the swap is an LS4 stripped down to block and heads, a custom 153 tooth billet steel flywheel with a 10.5" clutch, a dakota 2.5 liter AX-15 bellhousing and an AR5 trans. its all bolt together, no adapters. starter motor will be a ford variant mounted to a 4mm steel plate in the current pocket on the flywheel housing.

This is a luddite build, so knock-off victor intake, holley 830 CFM carb, and an MSD 6014. Heads will be either the 243's or 799's I have. probably the 799's as they are currently on the bench and I am currently porting them. Cam will be the summit 8702. going carb because I have been playing with EFI for nearly 40 years, and I am tired of parts that are NLA. plus I live in a state where the skyway bridge is the highest point at 210 ft above sea level, and the average temperature changes about 40 degrees year round.....so no choke.

the suspension is from an early C4 corvette, with coil overs and a 3.07:1 rear. may swap to 3.56:1. the car will either get air cups or bag riders to raise it up for speed bumps. Wheels are from a Z06

Everything that can not be sourced from various junkyards, ordered from various speed shops will be custom fabricated. That is pretty much everything but the basics of basics. that means custom fabricating the wiring harness, cooling water cross-over manifold, deareation tank, oil catch can, the adjustable custom reversed swing pedals (need the MC's angled upwards for room), the frame, exhaust, roll cage, tilt steering column, turn signal switch, HVAC ducting, air bag plumbing, etc. to save space, a portion of the roll cage will be the air tank. It also looks like I will be custom making a dropped base oval air cleaner to get the look I want as they do not make dropped base oval air cleaners.

This is not a catalog build where someone puts a swap kit in a catalog. this is a bit more intense than putting corvette suspension and a northstar V8 with a supercharger in an opel GT. I am not Chip Foose, or Dave Kindig, however I do my own sketches, designs, and fabrication and have the appropriate experience. I will also be doing my own bodywork and paint. this whole build will be built by me. and my target cost of build for the whole project is currently at $12k. with a bit of horse tradingand careful buying I do already have most of the motor, ignition system, driveline, suspension, wheels, fuel system, clutch, etc. in addition to the car itself and I am under the cost of a set of ported heads and an ECM

A while back I doodled my version of the crazy vs hot matrix for vehicle projects. its cool vs difficult this project is a solid 8-9 on the difficulty scale while being only a 4-5 on the cool scale currently.