No Accelerator at Cold
Thread Starter
Registered User
Joined: Feb 2022
Posts: 6
Likes: 0
No Accelerator at Cold Hello, I couldn't find anything on this in the search, but please let me know if the answer is already out there. Or if I have this posted in the right place.
I swapped an LQ4 into an old square body, 408 build. There have been a few small things that still needed ironing out, but generally it has been going well.
I am still using the stock throttle body, pedal and computer and had the truck tuned.
Now its winter though and if the truck spends the night outside in <0F weather and I start it up, it starts and runs fine, but it throws a MIL and has no throttle. I don't mean weak throttle response, I mean none. The gas pedal is completely dead. Restarting the truck does no good. If I disconnect the batter and hard reset it though, everything is fine. MIL goes off after a bit and its like nothing ever happened. Until the next time it spends the night a below zero temps.
Any thoughts? There is a bunch of stuff that is involved in the accelerator working, Pedal, TAC, Computer, Throttle body, wiring... I don't want to just start swapping stuff aimlessly.
I swapped an LQ4 into an old square body, 408 build. There have been a few small things that still needed ironing out, but generally it has been going well.
I am still using the stock throttle body, pedal and computer and had the truck tuned.
Now its winter though and if the truck spends the night outside in <0F weather and I start it up, it starts and runs fine, but it throws a MIL and has no throttle. I don't mean weak throttle response, I mean none. The gas pedal is completely dead. Restarting the truck does no good. If I disconnect the batter and hard reset it though, everything is fine. MIL goes off after a bit and its like nothing ever happened. Until the next time it spends the night a below zero temps.
Any thoughts? There is a bunch of stuff that is involved in the accelerator working, Pedal, TAC, Computer, Throttle body, wiring... I don't want to just start swapping stuff aimlessly.
Thread Starter
Registered User
Joined: Feb 2022
Posts: 6
Likes: 0
No. First time it happened it took me quite a while and the engine had run all the way up to operating temp and been restarted half a dozen times before I thought to disconnect and reconnect the battery. Second time it happened, I let it warm up to maybe 150F before going to the battery solution. Before going to the battery disconnect thing I tried plugging and unplugging and wiggling all the connectors between the pedal and the TAC and the Computer and the Throttlebody to see if maybe there was just a connection that got flakey in the cold, but nothing changed.
I'll see if the codes are still in the computer and post them tonight if they are.
I'll see if the codes are still in the computer and post them tonight if they are.
Cheap ELM 327 code reader off Amazon and Torque app for your phone will come in very handy.
Thread Starter
Registered User
Joined: Feb 2022
Posts: 6
Likes: 0
Thanks guys, I have a code reader. That's why I was saying I would grab the codes when I get home tonight as long as they are still in the computer. I'll post them up if they are still there. Going from memory they were TAC related.
Thread Starter
Registered User
Joined: Feb 2022
Posts: 6
Likes: 0
Ok, pulled the codes,
P1125 - Throttle Position Sensor Intermittent
P1516 - Throttle Actuator Control Module Throttle Actuator Position Performance
P2135 - Throttle/Pedal Position Sensor/ Switch A/B Voltage Correlation
Sounds like I have all the throttle codes going on here....
P1125 - Throttle Position Sensor Intermittent
P1516 - Throttle Actuator Control Module Throttle Actuator Position Performance
P2135 - Throttle/Pedal Position Sensor/ Switch A/B Voltage Correlation
Sounds like I have all the throttle codes going on here....
Trending Topics
TECH Regular
Joined: Feb 2002
Posts: 426
Likes: 45
From: ohio
If it goes int limp mode( idles very rough at 850 rpm or so and no throttle response) then more than likely the throttle body is bad. Mine did this intermittently when it was cold , but not all the time. Shutting off and letting it sit for a minute would cure it. It would do this at tip in off idle throttle as well
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Teching In
Joined: Jul 2015
Posts: 40
Likes: 5
I use a battery tender and if it is disconnected with a cold start immediately after the TAC module will sustain
damage resulting in an intermittent P2135 and/or P0120 . If the battery tender is disconnected twelve hours
before a cold start, the battery voltage drains to under 13V and there is no TAC damage on a cold start. The
TAC module is the weak link electrically.
f your battery is draining down overnight, then it's possible the TAC was damaged. The point being that battery
over or under voltage could cause the alternator to spike.
A rodent got into the engine compartment of my vehicle and chewed up the wiring between the fuse box
and the TAC module, the result was P1516, P2135 codes. The other wiring potential problem area would
be the throttle body connector, which can develop cracks in the wiring, replacement is PT3707.
When the codes are generated, are you saying it's goes into reduced engine power mode, where the
vehicle is still drivable, or is the throttle pedal totally dead? The latter case would indicate an intermittent
wiring problem.
damage resulting in an intermittent P2135 and/or P0120 . If the battery tender is disconnected twelve hours
before a cold start, the battery voltage drains to under 13V and there is no TAC damage on a cold start. The
TAC module is the weak link electrically.
f your battery is draining down overnight, then it's possible the TAC was damaged. The point being that battery
over or under voltage could cause the alternator to spike.
A rodent got into the engine compartment of my vehicle and chewed up the wiring between the fuse box
and the TAC module, the result was P1516, P2135 codes. The other wiring potential problem area would
be the throttle body connector, which can develop cracks in the wiring, replacement is PT3707.
When the codes are generated, are you saying it's goes into reduced engine power mode, where the
vehicle is still drivable, or is the throttle pedal totally dead? The latter case would indicate an intermittent
wiring problem.
Last edited by 88bruce; May 2, 2022 at 05:01 AM.
Thread Starter
Registered User
Joined: Feb 2022
Posts: 6
Likes: 0
The throttle pedal is completely dead. Re-starts don't cure it. It takes a battery disconnect and reconnect and then it runs fine. Next time it happens I also want to pay attention to idle speed. I figure if it goes to high idle and then steps down that at least the computer still has control of the throttle body and that maybe its the pedal. Or maybe other way around if idle never changes. Its tough to debug because I need to park the truck outside in <0F weather for it to be an issue. I could also try graphing the voltage on cold start next time I suspect its cold enough out for it to happen again...
Last edited by qr409tz8; Feb 3, 2022 at 12:01 PM.
TECH Regular
Joined: Feb 2002
Posts: 426
Likes: 45
From: ohio
More than likely the throttle body. It will run but it runs rough and stays at 850 to 900 rpm. It would sometimes take 4 or 5 restarts to correct the issue. Mine was intermittent, but got much worse when cold, to the point of doing it at in opportune times like in traffic on the freeway.
TECH Regular
Joined: Apr 2017
Posts: 424
Likes: 41
From: Worcester, Mass
Hello, I couldn't find anything on this in the search, but please let me know if the answer is already out there. Or if I have this posted in the right place.
I swapped an LQ4 into an old square body, 408 build. There have been a few small things that still needed ironing out, but generally it has been going well.
I am still using the stock throttle body, pedal and computer and had the truck tuned.
Now its winter though and if the truck spends the night outside in <0F weather and I start it up, it starts and runs fine, but it throws a MIL and has no throttle. I don't mean weak throttle response, I mean none. The gas pedal is completely dead. Restarting the truck does no good. If I disconnect the batter and hard reset it though, everything is fine. MIL goes off after a bit and its like nothing ever happened. Until the next time it spends the night a below zero temps.
Any thoughts? There is a bunch of stuff that is involved in the accelerator working, Pedal, TAC, Computer, Throttle body, wiring... I don't want to just start swapping stuff aimlessly.
I swapped an LQ4 into an old square body, 408 build. There have been a few small things that still needed ironing out, but generally it has been going well.
I am still using the stock throttle body, pedal and computer and had the truck tuned.
Now its winter though and if the truck spends the night outside in <0F weather and I start it up, it starts and runs fine, but it throws a MIL and has no throttle. I don't mean weak throttle response, I mean none. The gas pedal is completely dead. Restarting the truck does no good. If I disconnect the batter and hard reset it though, everything is fine. MIL goes off after a bit and its like nothing ever happened. Until the next time it spends the night a below zero temps.
Any thoughts? There is a bunch of stuff that is involved in the accelerator working, Pedal, TAC, Computer, Throttle body, wiring... I don't want to just start swapping stuff aimlessly.
I will add in I adjusted my [Engine Diag>Airflow>Calc Airmass - P1514 / p0068 Error] in HPtuners since the car is turbocharged and I wasn't sure if this was causing an issue as well. You did mention you had a 408 so perhaps it is sending the airflow out of spec but I'm not sure if this would contribute or not just thought it was worth mentioning.
Last edited by SwapStang; Feb 14, 2022 at 07:14 AM.
Thread Starter
Registered User
Joined: Feb 2022
Posts: 6
Likes: 0
Thanks SwapStang. This seems very plausible. I can certainly check the status of my ground and 12V on the TAC. My harness has been completely rebuilt so I can't guarantee those are as solid as they could be. The battery is fairly new, though I also cant guarantee that its not drooping at cold. The truck has been in the garage the past few weeks so no super cold starts for it meaning it hasn't had any issues since before I posted this.