Hey everyone, I recently bought an '06 Chevy 1500 with 200,000 miles on it. It didn’t have any codes when I first got it, but I noticed something odd with the shifting. It drove okay at first, but now I’m getting codes like P1516, P2108, and U0107, along with something for the MAF sensor. I already replaced the MAF sensor and the throttle body, but the same issues and codes keep coming back. I didn’t mess with any wiring, just plugged everything back in and reset it (I think), but I’m still having trouble.
I also noticed the gas pedal has a safety clip with a yellow mark on it, which makes me think it’s from a junkyard or has been replaced. Here’s the main issue: when I start the engine, it idles around 1000 RPM. But when I start driving, shifting feels off—around 10-15 mph, it should shift into 2nd gear, but it doesn’t until I ease off the gas. It’ll go up to about 2000-2500 RPMs before slowly coming down to 1000 RPM before it shifts. After that, other gears seem fine.
But the bigger problem is when I’m on the interstate. I was cruising at 65 mph and tried to speed up to pass someone. I hit the gas, and instead of accelerating, the RPMs shot up to 5-6k, but the truck didn’t go any faster. Feels like a throttle issue to me.
Should I try replacing the TAC (Throttle Actuator Control) module on the pedal or maybe check the wiring connected to it? I’ve got family who knows a lot about these trucks, but they haven’t seen this issue before, especially since it’s an electric throttle body. Any advice would be appreciated!
It definitely sounds like a TAC module issue, especially with the codes you’re getting. I’d start there. Sometimes the wiring can also cause problems, so check for any loose connections or fraying wires around the pedal assembly. The fact that the pedal looks like it’s been replaced could be a clue too. If replacing the module doesn’t fix it, it might be worth looking deeper into the wiring.
I had similar issues with my 2005 Silverado. Replacing the TAC module fixed it for me. If you’re seeing erratic RPMs and shifting problems, it’s a strong indicator that the module or wiring is failing. If you’ve already swapped the throttle body, that’s the next logical step.
I’d definitely check the wiring. The TAC module could be acting up, but wiring issues are super common with these trucks. A worn wire can throw off the whole system. Also, make sure your throttle position sensor is reading properly, that could be tied into the problem too.
Adi said: @Jordan
I’ll look at the wiring more closely this weekend. I hadn’t thought about the throttle position sensor—good call!
Yeah, I had a similar issue on an older truck I had. TPS was giving bad readings and causing all sorts of weird throttle problems. Definitely worth checking.
With those miles, I wouldn’t be surprised if the transmission is starting to slip. You mentioned the shifting feels weird, and if the engine’s revving high without gaining speed, that could be a sign. Have you checked the transmission fluid? Maybe give it a good flush if it’s been a while.
