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



crankedupforit
08-08-11, 09:54 PM
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.

darkman
08-08-11, 10:34 PM
See attached.

crankedupforit
08-08-11, 10:55 PM
Thank you sir.

Brackets
06-21-12, 12:55 PM
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.

danrob0123
06-21-12, 03:16 PM
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.

darkman
06-21-12, 05:44 PM
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/2004-2007-cadillac-cts-v-general/245357-darkman-got-one-you-throttle-body.html

See also attached.

Brackets
06-22-12, 01:52 AM
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.

Brackets
06-24-12, 02:20 AM
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.

crankedupforit
06-24-12, 10:12 AM
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.

darkman
06-24-12, 10:42 AM
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.)

Brackets
06-24-12, 01:32 PM
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/throttle-body-adapter-harness-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"?

crankedupforit
06-24-12, 03:54 PM
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.

Brackets
06-24-12, 04:19 PM
Yup, I hear you man, thanks again.

darkman
06-24-12, 07:08 PM
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?

Brackets
06-24-12, 07:41 PM
Yes, Darkman you are correct sir.

darkman
06-24-12, 08:03 PM
If it were mine, I think I would put the stock wiring and throttle body on it and have a shop with a GM TechII scanner (the local Chevy dealer maybe better than the Caddy dealer when it comes to LS engines) run through the diagnostics shown in the DTC-related pdfs. If the troubleshooting procedure came to the "replace throttlebody" instruction I would have them put the new throttlebody. In the mean time, I would verfiy with Katech and/or a multi-meter that their harness is not somehow assembled incorrectly.

Brackets
06-24-12, 08:48 PM
Yup, that's where I am right now pard. As soon as I got the car home from the GM dealership the 90mm TB came off along with the harness and it's back to the stock wiring and TB now. Of course once I did that the P0068 was gone but I got back the P0110, P0220 and P1516.

RoverGuy7
06-24-12, 10:49 PM
The P0068 isn't a MAFS code, it's a correlation code between MAFS and TPS. With the Maggie and the 90mm TB, you're pulling in more air at a given throttle position, then your ECM expects.
Given the timeline and what you have going on, I'd be thinking the P0068 is tune related, and your old TB was bad. I'm sure someone can post up what wires should be in what pins in your adapter harness, to make sure that's correct.

Brackets
06-25-12, 02:24 AM
I'm not ruling anything out RoverGuy. Thanks for posting.

RADEoN
06-25-12, 10:21 PM
i actually agree entirely with roverguy, and that was going through my head as well. P0068 Is Throttle Body Airflow Performance... so it's possible your new throttle body might not be any good either?

I'm assuming you've tried replacing the MAF at this point?

Brackets
06-26-12, 10:58 PM
No RADEoN I haven't replaced the MAF. I'm not even confident that that P0068 is a real or valid code as it never showed up until the GM tech switched wires around in my brand new Katech harness. The car has the old LS6 TB on it again and is throwing the old P0120, P0220 and P1516 codes. The LS2 TB was throwing these same codes with NO P0068 until he switched wires around.

RADEoN
06-26-12, 11:02 PM
try a stock ls6 throttle body if you can get one.

carlson_mn
07-30-12, 11:09 PM
first thing I thought was change that MAF. Any resolution to this?

etcts-v
07-31-12, 06:41 AM
Yeah any resolution? I'm having the exact same problem!

crankedupforit
07-31-12, 04:46 PM
Check the wiring harness. Here's what I found on mine. Looks like a rat chewed it. Needless to say this caused some P2101 and P1516 issues. The car also drives much better at low speeds. See blurry phone pic below.

http://i1073.photobucket.com/albums/w382/mikesummers/Trailerpics003.jpg

etcts-v
07-31-12, 10:41 PM
Wow the stealership missed that! Thanks for The pics I'll check mine out thoroughly!

OneFast V
11-18-12, 11:32 PM
So I was at Thunderhill raceway and during my third session coming into the 2nd to last turn the throttle began to feel funny and my car shut into REP mode. luckily was close to the track exit and limped back to the paddock. When i pulled up all my codes i was getting p0120, p0220, p1516 & p2101. I checked the connections and looked for cracks or any signs of a bad wire and nothing. Is it possible my throttle body just died out on the track? The car stil turns on but just idles like pure crap and seems to surge. It is an LS6 with a maggie on it. anything else to check? (i have a ls2 90mm throttle body sitting in the garage waiting to go on.) Should i try the other throttle body? what is my next step?

darkman
11-18-12, 11:44 PM
P1616 is not a listed diagnostic trouble code, but I think P1516 is what you have. See attached.

OneFast V
11-19-12, 12:11 AM
P1616 is not a listed diagnostic trouble code, but I think P1516 is what you have. See attached.

Correct p1516

barrok69
11-19-12, 10:21 AM
So I was at Thunderhill raceway and during my third session coming into the 2nd to last turn the throttle began to feel funny and my car shut into REP mode. luckily was close to the track exit and limped back to the paddock. When i pulled up all my codes i was getting p0120, p0220, p1516 & p2101. I checked the connections and looked for cracks or any signs of a bad wire and nothing. Is it possible my throttle body just died out on the track? The car stil turns on but just idles like pure crap and seems to surge. It is an LS6 with a maggie on it. anything else to check? (i have a ls2 90mm throttle body sitting in the garage waiting to go on.) Should i try the other throttle body? what is my next step?

I just went through with this issue when I first bought my car used a few months back. I also have 2005 LS6 maggied. I had to replace the Throttlebody. I diagnosed the Commanded throttle position angle not corresponding to the actual throttle angle and that's what sets the series of faults.

The ecm does a check each time you start the car or shortly thereafter continually and if it fails it dumps you into reduced engine power mode :( I thought just doing a battery reset would take care of it... and it did for about 20mins until it came back again.

I also tested the accel pedal using a tech2, but it was tracking fine. All signs pointed to new TB. I replaced it and problem solved. You can pick up lightly used TB's from most local engine build shops for cheap as they ditch them for bigger or non drive-by-wire setups for old hot rods etc.

I thought about just replacing the throttle plate motor, but I heard these TB assemblies are pretty well calibrated and finicky if you play with them much, plus replacing the entire thing with a known working version was a better option. You should be able to get one for under $200. Unlike the $800 that the dealership is asking.

Regarding your LS2 TB... It has a different bolt pattern (4bolts) versus (3bolts on the ls6) and the electrical connector is different as well.

CTSV_510
11-19-12, 12:42 PM
Yup, this just happened to me for the second time in 15 months. First time was the stock ls6 TB so I upgraded the Maggie snout to the 90mm and ls2 TB and now that one gave up too. I got another one from scoggin dickey... Crate motor take off for $225. I can't believe I've had two TBs die on me.

Twitch
11-19-12, 01:44 PM
My TB pooped out on me at Pocono. It wasn't any fun driving back to NYC like that but she got me home!
If you have the wireing adapter, just plug in the LS2 TB. Turn key to the "ON" position. If the codes clear right away just swap out TBs.
Good luck

crankedupforit
11-19-12, 04:05 PM
I had the fault in the ECU removed from the tune. I think that these TBs don't like the constant modulation of the throttle experienced on the road course. I say that but plenty of folks never have issues. The worse thing that can happen is the throttle blade can stick open (remember cars with carbs?). It will then bounce off the rev limiter so you can shut the key off to kill the motor. Certainly nothing wrong with swapping out the TB. If the code doesn't reset after restarting the engine then perhaps the TB is bad. Mine always reset perfectly every time. It just failed during WOT.

Brackets
12-07-12, 07:49 PM
So thought i'd post an update. The saga continues with no resolution yet. The mechanic (ex GM, retired) who I had working on the car replaced the tac module. That would have been the next thing that I would have suspected and replaced. No change, so he spent countless hours (his words) chasing all the related wiring and found no problems until he got to the ecm.

Upon removal of the wiring connectors from the ecm he found significant corrosion on the lower section of pins. Much cleaning of pins and connector didn't help so he figured the ecm was shot. I ordered a ecm from Jesse at wait4me because I needed one with a tune for the Maggie. After installation of the ecm from Jesse all the trouble codes went away but still reduced engine power and service stability system come up on the dic. At this point the mechanic I had working on it threw in the towel and I limped it home to my father in laws.

I tried swapping my old ecm back in and got the P0120 P0220 P1516 codes back as well as Reduced Engine Power. Swapped the ecm from Jesse back in and the trouble codes are gone but Reduced Engine Power and Service Stability System come up on the dic as well as Service Vehicle Soon. Did a relearn and Service Theft System went away but still had Reduced Engine Power and Service Stability System with no trouble codes or check engine light. Put my old tac module in and I got Service Vehicle Soon along with the old Reduced Engine Power, no check engine or Service Stability System.

One thing that I question somewhat and that I haven't spoken to Jesse about yet is the fact that my ecm was part #12589462 and the one he sent me was #12576106. I realize that some of these ecm's are similar but from reading on a listing from an eBay vendor some are not. Can anyone shed any light on this or have any other ideas to add? Thanks for reading.

crankedupforit
12-07-12, 08:20 PM
Consider removing the faults from the tune. You can adjust the milleseconds which the throttle blade and the accelerator pedal position can be out of sync. Even with mine opened up to the max I still got the codes. I had the tuner remove the faults from the software. Worse case scenario is if the throttle sticks open you'll have to shut off the engine.

darkman
12-07-12, 08:46 PM
I found a couple TSB involving electrical "ghosts."

Crankedupforit's approach has some appeal.

Brackets
12-08-12, 01:48 PM
Thanks for the comments. Crankedupforit, do you mean to have the specific faults removed or can you have just the reduced engine power mode removed? I only get the codes with my original ecm, the ecm that I bought from wait4me doesn't throw codes but they both put the car into reduced power mode.

crankedupforit
12-08-12, 04:29 PM
Yes, you would remove from the tune the fault trigger when the commanded throttle position from the gas pedal is different from the actual throttle body blade position. It's probably not even off but the ECM thinks it is. One of those faults throws the car into limp mode. I'm not sure why your new ECM doesn't set up a code when it goes into limp. Doesn't make sense since it is definitely a fault and should record an event. I'll email my tuner and ask specifically what tables he worked on for you.

Brackets
12-10-12, 04:33 AM
Appreciate that pard. Here are a couple of pics of the corrosion that was in my original ecm.

http://www.cadillacforums.com/forums/attachments/2004-2007-cadillac-cts-v-general/100991d1355128216-p1516-command-vs-actual-throttle-position-20120925_151341-large-.jpg

http://www.cadillacforums.com/forums/attachments/2004-2007-cadillac-cts-v-general/100992d1355128235-p1516-command-vs-actual-throttle-position-20120925_151401-large-.jpg

http://www.cadillacforums.com/forums/attachments/2004-2007-cadillac-cts-v-general/100993d1355128254-p1516-command-vs-actual-throttle-position-20120925_151423-large-.jpg

Brackets
12-12-12, 04:20 AM
Darkman, if you're still watching this thread would you have any info available on the grounding locations? I've only checked the one on the rear of the engine block drivers side and it looked brand new. I'm sure there are others too? That's the only other possibility I can think of causing this issue.

darkman
12-12-12, 07:54 AM
Darkman, if you're still watching this thread would you have any info available on the grounding locations? I've only checked the one on the rear of the engine block drivers side and it looked brand new. I'm sure there are others too? That's the only other possibility I can think of causing this issue.

See attached.

Bad grounds on this car may appear okay because: (a) the deterioration can consist solely of a thin coating of oxidation; and (b) they may still work well for high voltages but fail as a low voltage reference. So it is a good idea to freshen the grounds with a small file, emery paper, or the like. Also star washers are your friend.

crankedupforit
12-12-12, 10:28 AM
Brackets
I've PMed you with the fix for certain DTC process enablers not to report. This should fix your issues but be aware that in the unlikely event the throttle blade should ever jam open, the engine will bounce off the rev limiter and you will need to shut down the motor by turning off the key. Good luck.

barrok69
12-12-12, 10:42 AM
Yup, that's where I am right now pard. As soon as I got the car home from the GM dealership the 90mm TB came off along with the harness and it's back to the stock wiring and TB now. Of course once I did that the P0068 was gone but I got back the P0110, P0220 and P1516.

Replace Throttle Body or Pedal assembly. All your problems should be solved.

Given that you have already replaced a bunch of things I would do a control test and put your LS6 hardware back on and swap out the pedal. I had the same issue with my car when I first got it. I've done alot of research on the topic of those codes and basically narrowed the issue down to 4 items. Throttlebody is bad, Pedal is bad, Bad grounds, or TAC module is bad. I had a tech2 hooked up and cycled the pedal and it was tracking normal, so that eliminated that. I noticed with the TB that the commanded position was off slightly from actual and that's what was triggering the fault. It will never fix itself. I replaced the TB and everything has been fine since.

Since you've already replaced or at least have a replacement TB, we can probably eliminate that, unless you bought it in "unknown" used condition. You've replaced the TAc module with no change. You've checked the grounds. The last thing that is associated with the P codes is the actual pedal assembly. They are available on rockauto for $120.

Hope that helps you a bit. And I would probably change your katech harness back to normal if you are going to use the 90mm.

Brackets
12-12-12, 01:49 PM
Thanks for the pm pard. Do you think by eliminating these that there would be any reduced functionality of the tc or stability systems? Darkman, as always, appreciate the attachments man, you're an awesome asset to this site.

----------

Barrok69, thank you for taking an interest. That's the thing that's so frustrating about this whole thing for me is that all this stuff has been replaced. The throttle pedal assembly was one of the first so unless I got a bad one from GM I think I can rule that out. The tac module was a GM rebuild put in by the mechanic who I had looking at the car to the tune of $415.00 for just the part. The 90mm throttle body was a brand new take off that I bought off a reputable forum member and had come from Katech along with the Maggie snout and wiring harness so I think that I can rule that out as well. Since this mechanic has had my car the problem has actually gotten worse. When I took it to him I did have a little throttle response and now I have absolutely none. Another thing that troubles me is that when I do the throttle body relearn by putting the pedal to the floor and cranking the engine, its not supposed to fire and it always does. I sure wish I had access to a tech 2.

Brackets
12-15-12, 11:46 PM
Got a call in to Jesse and asked about deleting the codes out of the computer. He told me that he already had done that and always does that just so guys don't have problems after doing engine mods then having to send their computers back in to be adjusted. I guess that would explain why my old ecm was throwing codes and the one from Jesse wasn't. Back to checking wiring and grounds.

crankedupforit
12-16-12, 10:55 AM
Sorry to hear that. Hope you find the issue. Maybe Jesse's tune wasn't throwing codes but it was/is enabling the limp mode when an event occurs..... no? Maybe I'm confused but I always assumed reduced engine power is a command from the tune and can always be added, changed or deleted.

dedeaux89
06-16-13, 12:49 PM
Was there any solution to this, I'm in a quite similar situation with my FAST 102 set up that I just put on

AAIIIC
12-16-15, 01:55 PM
I got "Reduced Engine Power" about 1/2mi from home last night while returning from running some errands. Pulled into the driveway with the car idling like crap, grabbed my code scanner and pulled P1516 and P2120 (or P2021? whatever...). I reset the codes and the car immediately started idling normally. I was surprised at that, as the idle was so bad when it was "broken" that I figured something was really wrong and the codes would immediately set again after I cleared them. My guess is that the "Reduced Engine Power" settings just don't play well with my engine combination & tune.

Anyway, I looked up the codes and found out they're related to the throttle position. I pulled off the LS2-to-LS6 throttle body adapter harness [I have a 90mm TB on my LS6], gave it a thorough once-over, cleaned all the connections with DeOxit, and put it back together. I just moved, and haven't really unpacked the garage yet, so I couldn't find my multimeter to do any sort of continuity checks while wiggling the wires around or anything like that. The car started and ran just fine last night, and drove to work without issue this morning, but of course I'm worried about the long term - seems like a few folks have had recurring issues with this and replaced parts, sometime without getting resolution.

Has anyone had these codes and found them to be due to an LS2-to-LS6 adapter harness? Or is it typically the TB itself that is the issue?

[On a related note, I went searching for information about these codes, read a thread that OnefastV had started, then merged that thread with a couple others on the same subject. In doing that, the DTC procedure PDFs that Darkman had attached (to what is now post #28 in this thread) disappeared. :confused: So, Darkman, if you see this, feel free to re-upload the P0120, P0220, P1516, and P2101 PDFs. :) ]

darkman
12-16-15, 02:27 PM
See attached.

I also have the LS6 to LS2 throttle body conversion harness. I experienced the reduced engine power condition together with the same error codes one time. I pulled off the road and let the car set 10 minutes and it restarted and ran normally. The condition has never recurred, but I did add redundant grounding after that (ground strap from hood strut to passenger side head + ground strap from passenger side to driver-side head). I still have the same conversion harness, so I assume it is good.

AAIIIC
08-07-16, 05:56 PM
I'm running a 90mm LS2 TB with an adapter harness on my LS6. The TB and harness were installed on the new engine that I put in ~4 years and 60k miles ago. I bought the TB used, but don't recall what mileage it may have had on it.

So, over the past 8 or 9 months I've had about half a dozen P1516 codes. The first one happened back in December last year, as posted above. I cleared the codes, checked the wiring harness and connectors, and all was good to go for 4 or 5 months. Then I had a batch of 3 within a couple days of each other - the first 2 were both during a ~4hr drive home from a track event, and then the 3rd one happened shortly thereafter. Once again I pulled the adapter harness, made sure all the pins were good, used some Deoxit cleaner, and thought that had fixed the issue.

Fast forward about 3 months and now I've had another batch of 3 codes in the past two weeks or so. I haven't done any additional troubleshooting yet - just keeping the code reader handy so I can reset the CEL if the code pops up again.

Each time this has happened it's been while I'm just cruising along at part throttle - most of the occurrences have been on the highway doing 65-75mph, and another couple happened while running errands on local roads doing 40 or 50ish.

From what I've read, there are two TPSs, one that goes 0-5V and one that goes 5-0V. The TAC module compares / adds the two TPS signals, and if that doesn't check, it pops the code. My thinking is that one of the TPSs is developing a "dead spot" where the throttle spends most of its time, but that's just a guess. I suppose it could also be a similar sort of dead spot in the throttle pedal. I don't think it's the adapter harness - I've given it a pretty thorough inspection and cleaned all the contacts.

Any thoughts on how to track down the source of the P1516 code? Stupid question - where is the TAC module? Is it part of the motor assembly on the TB itself, or is it mounted elsewhere?

darkman
08-07-16, 07:24 PM
See attached.

AAIIIC
08-07-16, 08:07 PM
Ahhhh, it's the box mounted on the side of the big fuse box in the engine bay. That's easy to get to, I can check the connections on that and clean them up.

Thanks!