Throttle Body Replacement-P1516 Code Returned

Hey guys truck is a 2003 1500HD Silverado with the 6.0L 364V8.
Last winter I started getting the P1516 code and reduced engine power randomly during driving. After dealing with it for about a month I did some research and discovered in most cases it was either the wiring/plug or the TAC module itself. After going over the connections I couldn't see any visible breaks..etc but I decided to go ahead and change out the connector and about 6inches of the wiring.

After replacement the code hadn't come back until today, probably atleast 9months ago was the last time it did it. Today the code came on four times during a 10minute drive. Before it would come on once during the drive, i'd clear it with my scan gauge, and it would not do it again the entire day. I checked all my connections once again and everything is intact and there is no visible breaks and the connector is clean. I'm starting to think that it was just a concidence that this problem quit when I replaced the connector, and was wondering if colder weather could have weight on this issue?

After poking around the posts on here and other sites I found that many ended up replacing the TAC module which is on the throttle body. After looking at mine the only way I can see replacing that is just buying a new throttle body with the TAC on it, can't seem to find just the TAC part by itself anywhere. So if I were to order a new throttle body how hard is it to remove/install? and do I have to do a relearn process or is it plug and play?? Any insight to this would be great, I hate to throw parts at something not knowing the true problem so if I'm looking in the wrong direction please let me know.
Thanks for the help.

did you use heat shrink wrap when you did the repairs last year??if not might try that
as far as replacement its usually easier then replacing a carb.if you've never done 1 its not a tough job.good luck

this TAC is nothing but a resistor..as the throotle is moved the wiper in this rotates varying the resistance..

if carb cleaner or acid cleaning solutions where used this would destroy these parts..

It is possible this is the problem. you must use a ohm meter and with the engine off battery ground removed measure for the resistance to vary smoothly when throttle is moved..

Thanks for the responses guys. When I redid the wiring and plug they gave me a set of butt connectors to rewire with the exsisting harness but since I wanted it done correctly I did use heat srink wrap when I did the repairs. Not sure if it would help or not but I've have tried several times wiggling the plug and harness with the motor running and someone moving the throttle through the RPMs and have never been able to recreate the problem. So thats why I hope the harness isn't the issue.
Thanks for the idea JCAT, hadn't thought of that and I will give it a try. The only thing I do not understand is today I drove the truck several times and to and from work and the problem never happened once. How could it go from happening 4times in one driving cycle to not happening at all in several cycles? It is a very random problem and hard to recreate thats for sure. Is it possible moisture could be getting in somewhere causing this problem? Anymore ideas would be great and I will post back with what I find out.
Thanks again.

because of the saftey concerns with the throttle control signal, it is very sensitive. this computer in these vehicles is extremely sensitive..

to really make sure its the throttle resistor , monitoring the signal voltage with a scope would be great to be totally revealing.

I would solder the new connector in place then heat shrink..
also on the connector pins place a little silicone electrical grease this will keep the mositure out and other corroding chemicals....

could also be the wiring and the computer connectors..

Hey all,
Still experiencing this problem very intermittingly which is making it hard for me to check values at the TPS when running etc. I can't get it to repeat the problem enough to check. I undid all my wiring checked each wire individually once again and resoldered and heatshrinked them back together. Didn't change the problem, still coming up.
The weird thing about it is when the issue occurs it will be right at the begining of the drive, maybe 5-10mins into it. The reduce power message comes up and P1516 comes on my scan gauge. I clear the code. Truck returns to normal and code will not come up again the rest of the day, regardless of how many times I drive it.
Been doing more research and found a few TSBs saying a loose/corroded ground wire could be to blame. I checked and cleaned all obvious grounds I could find, but the ground referred to in the TSB was G103. This ground is mounted to the right rear cylinder head (passenger side) the note is that the ground is difficult to get too. I haven't been able to locate this ground or find more detail on its location. Was wondering if any of you guys could help me better understand where it's at and the best way to get to it. I would like to get all the grounds cleaned before I move on to the next step. Any help would be great. Thanks.

ground conection should be just under vale cover.(back of head)if you cant feel it you should still be able to feel the bolt if no bolt ck othe head

Well found the other two grounds I was looking for, sanded them off and replaced them and of course that didn't fix my problem. I was able to get the truck up to a real scanner today and pulled the freeze frames from when the code was thrown and it seems to be the TAC at fault.
I went ahead and ordered a new throttle body w/ a new TAC on it and it should be here tomorrow. Looking at the one on my truck all I see is three bolts, the wiring harness and a coolant line going into the throttle body and another one leaving the other side. Is there anything I should worry about when replacing this part. Should i worry about air getting into the coolant system? Or loosing to much coolant when removing these two small hoses. The removal/installation looks pretty basic but I would like some more knowledge before I set out to tackle this job.
Any light you guys can shed on this would be great. Thanks again for the help and I hope this will finally fix my problem for good.
Thanks Danny.

It appears that on your model the throttle body will need replacing...to get the TAC replaced.. cost 200.00 ..

before you replace it check the wires under the fuse block above the PCM/computer...could be damaged chaffed wires...

those connectors are also very expensive for this TAC...

drain the radiator then with diapers/hazmat material place to prevent coolant from leaking into the upper intake area where the knock sensors are and away from other componets...

to purge air when completeting this run engine with coolant cap off continue to fill until engine is hot...rev to 2,ooorpm a few times..this is how to get the air out..

Hey guys,
Just wanted to let ya know I installed my new throttle body on Tuesday and for the most part the install went with out a problem. I've been driving the truck quite a bit for the past few days and am yet to see the P1516 code return. I think after a few weeks/month with no return I may have finally fixed my problem. Also with this new part on I did find much smoother idle and even a slight improvement in throttle response as well. Do you think that is just because of it being a new part? The old one did have some carbon build up on it, but nothing too terrible.

Well I will keep you guys updated if the code returns, thanks to Jcat and inafogg for the help, greatly appreciated. If anyone ever gets this problem with their truck I have tons of info, tsbs, TAC value charts..etc if you ever need it. Just let me know. Thanks again.
Danny

that sounds good..too bad this part required the intake to be replaced.

keep the carb cleaner away from this engine ....it is destructive to the non metalic parts...

yes replace the throttle body I had mine replaced and everything is fine now.I wish I would have done this years ago. My truck is a 2003 2500 HD.:rofl:

yes replace the throttle body I had mine replaced and everything is fine now.I wish I would have done this years ago. My truck is a 2003 2500 HD.:rofl:


i have a 2003 cadi escalade.. having the same problem! ive replaced the TB, had the PCM flashed, and replaced the ground at the TAC module... still having issues. any ideas???

I still have had no problems since the TB replacement..

i did too... but with a remanufatcured part. did you do a brand new TB?

Yes I had it replaced with a new part.I hope you get it fixed.I was going nuts with the problem,until I changed it out.