P1516 Command vs Actual Throttle Position Performance (TAC Module)
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2004-2007 Cadillac CTS-V General Discussion Discussion, P1516 Command vs Actual Throttle Position Performance (TAC Module) in Cadillac CTS-V Series Forum - 2004 - 2007; Threw this code today at the track during the 3rd session. Car went to reduced power mode so I limped ...
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    P1516 Command vs Actual Throttle Position Performance (TAC Module)

    Threw this code today at the track during the 3rd session. Car went to reduced power mode so I limped back to the paddock, read the code, restarted the car and is was back to normal power, cleared the code and went back on for the next session. Never did it return. Anybody have an idea what caused this? Darkman? I have an LS6 with a LS2 style Nick Williams TB that required an adapter harness.

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    Re: P1516 Command vs Actual Throttle Position Performance (TAC Module)

    See attached.

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    Re: P1516 Command vs Actual Throttle Position Performance (TAC Module)

    Thank you sir.

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    Reduced engine power, P0120 P0220 P1516 and P2101 (search is not working)

    So I've been getting "reduced engine power" mode for a while now. It started intermittently and has increased to the point where it goes into this mode as soon as I turn the key. The V is is a Maggied '05 LS6 so the first thing that I tried was replacing the TPS on the throttle body, no change. I wanted to eventually swap to an LS2 90mm TB so now seemed a good time for that. Swapped in a 90, new snout, and wiring harness, no change. Spoke with some local GM guys and figured it had to be the accelerator pedal so new pedal assembly ordered and installed, no change. One other thing to note here is that I tried a TB relearn after this and the engine started, it's my understanding that it should NOT. I also removed the ground wire from the back of the drivers side head, it was still shiny but I cleaned it anyway. Other than that I've visually checked and continuity tested what wiring and connectors that I could. Any other ideas before I take it into the dealership? We don't have a Caddy dealership locally so it's going to GM for a tech II read if I can't figure it out. Thanks for reading.

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    If you've already replaced all the parts that would have to do with the codes you are getting, I would check and re-check all the wiring/electrical connections. I read that the most common cause for these group of codes is a crimped wire near the throttle body. If all the wiring/connections look good then I would either wait for someone else to chime in on here or take it to the dealer.

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    Re: Reduced engine power, P0120 P0220 P1516 and P2101 (search is not working)

    Quote Originally Posted by Brackets View Post
    So I've been getting "reduced engine power" mode for a while now. It started intermittently and has increased to the point where it goes into this mode as soon as I turn the key. The V is is a Maggied '05 LS6 so the first thing that I tried was replacing the TPS on the throttle body, no change. I wanted to eventually swap to an LS2 90mm TB so now seemed a good time for that. Swapped in a 90, new snout, and wiring harness, no change. Spoke with some local GM guys and figured it had to be the accelerator pedal so new pedal assembly ordered and installed, no change. One other thing to note here is that I tried a TB relearn after this and the engine started, it's my understanding that it should NOT. I also removed the ground wire from the back of the drivers side head, it was still shiny but I cleaned it anyway. Other than that I've visually checked and continuity tested what wiring and connectors that I could. Any other ideas before I take it into the dealership? We don't have a Caddy dealership locally so it's going to GM for a tech II read if I can't figure it out. Thanks for reading.
    Read this thread and the attachments thereto: http://www.cadillacforums.com/forums...ttle-body.html

    See also attached.

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    Re: Reduced engine power, P0120 P0220 P1516 and P2101 (search is not working)

    Okay thanks for the replies. Darkman, that thread that you linked looks like a possibility although mine isn't hunting like that. Hopefully post a resolution tomorrow.

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    Re: Reduced engine power, P0120 P0220 P1516 and P2101 (search is not working)

    Well $300.00 later I get a call from the dealership "we were able to clear all your codes" so I go in to pick up the car and they tell me I now have a new code P0068, a mass air flow code and still in "Reduced engine power". What did you do to fix it I ask? "I swapped the green and purple wires in the harness" he tells me. "Which harness" I ask already starting to get a bad feeling. "The throttle body harness" (Katech LS6 to LS2 adapter harness). "Really?, those guys make a lot of those harnesses I really doubt that they would mix up those wires like that". "Maybe you should put your old throttle body back on and then the mass air code will go away". Great! I limp the car home again, swap snout, throttle body and remove the Katech harness and I'm back in the same boat, P0120, P0220 and P1516 "reduced engine power". So basically I guess I paid to have my codes read for me and for the "GM tech" to surf the web, very little real trouble shooting by following the service manual procedures. My fault I guess, shouldn't have confused them with an LS2 TB on an LS6. The weird thing is the codes were gone and I could do a proper TB relearn (no start). Before, and now again that I've put the old TB back on, it was starting on a relearn which I understand it should not do. One other thing, I didn't think that there would be a problem (codes, reduced engine power) putting the LS2 TB on. I knew that I would have to get it retuned of course but I was told by the tuner that I should be able to drive it.

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    Re: Reduced engine power, P0120 P0220 P1516 and P2101 (search is not working)

    The TB scalar in the tune program knows the size of the TB. When switching from a 78 to a 90 this has to be reset into the tune. You have you gone into the ETC Area Scalar and appropriately increased the values for the increase in TB size?
    Although the car may run, it certainly has the TB flow confused. That may be the issue since the amount of air flowing does not match the tables that are set in the tune.

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    Re: Reduced engine power, P0120 P0220 P1516 and P2101 (search is not working)

    I believe, based on the codes and the associated informatation that basic issue is the PCM's inability to determine (or perhaps use if the PCM is bad) the indicated throttle position. The other thread I referenced does contain a list of the wires colors, including the correction of a mistake in the Service Manual. It sounds to me like the dealer got caught up in the throttebody change and wiring and did not run the rest of the troubleshooting chart to eliminate stuff like the TAC module.

    (I am skeptical that this problem relates to the change in throttlebody size and its affect on the tune. I ran an LS2 90mm throttlebody on an LS6 78mm throttleboyd tune for months and got no DTCs, experienced no reduction in fuel economy, and performance was improved. I understand, based in part on a detailed explanation by CTSVmapper, that the tune was "suboptimal" but I think the error involved "air flow" as opposed to the mechanically determined position of the throttle.)

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    Re: Reduced engine power, P0120 P0220 P1516 and P2101 (search is not working)

    Thanks for chiming in crankedupforit but I'm leaning towards darkmans thinking on this. The first thing that puzzles me is why the tech should have to switch those wires (which I make out to be purple, 5v reference on TP sensor 1 and green, low reference TP sensor 2) in the brand new Katech TB converter harness PN: KAT-4752 http://store.katechengines.com/throt...rness-p20.aspx . I mean, it's not even like those wires are even beside or above and below each other so I just don't see how they could have been inadvertently mixed up at Katech. The other thing is that I do know and had expected to have to retune but I just don't think that I've ever seen anyone throwing mass air flow codes after an LS6 to LS2 swap. That wire swap just doesn't sit right with me. And yes, I think the tech got very sidetracked in his diagnosis by the LS6-LS2 issue. Also does anyone know for sure if a mass air flow code will put the car in "Reduced power mode"?

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    Re: Reduced engine power, P0120 P0220 P1516 and P2101 (search is not working)

    Darkman knows his stuff and his approach is a good one. The only reason I mentioned the scalar values was I am having the same problem but only on the track when the car gets warmed up it throws P2101s and goes into limp mode. I bought a new Katech harness and a new TB just in case but several corvette vendors at the track keep mentioning the scalar values and other tuning aspects to this problem. The problem with these codes is they can take a lot of trial and error to solve ($) from the TAC module to the PCM to the TB to the harness to the tune etc. I just don't know where to begin.

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    Re: Reduced engine power, P0120 P0220 P1516 and P2101 (search is not working)

    Yup, I hear you man, thanks again.

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    Re: Reduced engine power, P0120 P0220 P1516 and P2101 (search is not working)

    Well Darkman is guessing on this one. As I understand it though the problem existed with the old throttebody and wiring harness - is that correct?

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    Re: Reduced engine power, P0120 P0220 P1516 and P2101 (search is not working)

    Yes, Darkman you are correct sir.

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