P1516 code ?

I have just bought this 2003 1500 HD Silverado with 123,000 miles on it. It has went into reduced power mode and thrown this code 3 times since I bought it. I have cleaned the electrical connectors on the throttle body and the TAC module with electrical cleaner and put die-electric silicon grease on them before connecting them back together. I have driven about 800 - 1000 miles in several trips since doing this and it has worked perfectly. Do you think I have solved my problem or is it going to do it again when I least need it to? Any speculation will be greatly appreciated. The truck has the 6.0 and 4.10 gears.

I dont remember that code off of the top of my head, whats the definition?

The P1516 is command vs actual throttle position Performance (TAC module). I also cleaned the butterfly in the throttle body.

your problem was a widespread GM defect..TSB's all about this...the sensor is suseptible to damaging chemicals/other materal that enters and damages this componet...

with your actions if this were done in 2003 I would say it would never have happened...

do not use any chemicals /or wash engine near this componet..

you are aware that if this needs replacement , the complete throttlebody is the total componet....

I had this same issue with my truck and it was extremely intermittent at the beginning. If you do a search on this site or on google you will see it has happened quite a bit like Jcat commented. I had this problem show up last winter ('08-09) thought I had the issue fixed but it in fact returned about 9months later. I will you give you the link to my thread I started on the issue just in case your problem comes back up again. Also quite a bit of info online including technical safety bulletins, flow charts, troubleshooting..etc I had even read reports of accidents being caused because of this. I will admitt that it makes you pucker up a little bit when your crusing down the street at the speed of traffic and all of a sudden your truck turns into a limp noodle, thank god it never happened to me on the highway...pretty dangerous. Here's the link to my thread:

http://www.automotiveforums.com/vbulletin/showthread.php?t=972106

Is it usualy the TAC itself and not the module on the firewall by the steering shaft and master cylinder? I had a chevrolet mechanic tell me it was this module that was bad. From what I have read on this forum it seems to be the TAC that is most often the cause of this problem. Sort of makes me want my 94 GMC Z-71 back. The old 350 was pretty reliable.

I think you nailed it, because water + electronics don't mix.

Any lost electrical signal from the pedal to the throttle body will cause a Reduce power mode!

You probably saved yourself $1K, by doing it yourself right the 1st time.

Hey , Folks. Thanks for all the info. I have a 2003 Chev silverado 2500 6.0. 214,000km. I have BBK shorty headers and a K/N cold air intake. keep all regular maintenance oil change tune ups etc. burn only high test fuel. having same problem with reduced engine power:frown: But only since i put the headers on. had truck for 2 years and just put headers on Aug this year. Next day it started. Been having problem mostly when i first start driving. But today i left my scan tool plugged into it while i was driving. It went into reduced engine power i pulled over left it running and cleared the code and it went back to normal. Ran perfect. Any ideas???

Hey , Folks. Thanks for all the info. I have a 2003 Chev silverado 2500 6.0. 214,000km. I have BBK shorty headers and a K/N cold air intake. keep all regular maintenance oil change tune ups etc. burn only high test fuel. having same problem with reduced engine power:frown: But only since i put the headers on. had truck for 2 years and just put headers on Aug this year. Next day it started. Been having problem mostly when i first start driving. But today i left my scan tool plugged into it while i was driving. It went into reduced engine power i pulled over left it running and cleared the code and it went back to normal. Ran perfect. Any ideas???

get the code pulled , if it is the 1516 then the throttle body tac maybe worn out..with a ohmmeter you can measure the resistance as you move the throttle to see if the resistance does not jump/should change smoothly.

why do you use high octane ? not necessary !

headers can cause engine problems , if this increases the vibration/noise the knock sensors will retard the timing ..this will cause low power and poor MPG.

the wires and connector could be bad..to the TAC...

Is this a Drive by wire instead of cable?

Is this a Drive by wire instead of cable?

yes . this was the first year ...110% failure rate.. as mentioned very dangerous if on the hywy...

if the tac has a bad spot in the sender or the connector is corroded the pcm reduces power to prevent a potential toyota runaway condition.

yes it is drive by wire. btw thanks for the quick response. i use high octane because the truck seems to idle smoother and i had a code flash for low output knock sensor bank 2 when i first bought truck 2 years ago. cleared code. ran high test ever since havent had issue since. switched to headers because had 4 out of 12 heads broke off exhaust manifolds. So had to pull off to replace bolts so figured put on headers. tons of power in higher rpm range. but having this problem now. think i should change knock sensors and switch back to regular gas??

yes it is drive by wire. btw thanks for the quick response. i use high octane because the truck seems to idle smoother and i had a code flash for low output knock sensor bank 2 when i first bought truck 2 years ago. cleared code. ran high test ever since havent had issue since. switched to headers because had 4 out of 12 heads broke off exhaust manifolds. So had to pull off to replace bolts so figured put on headers. tons of power in higher rpm range. but having this problem now. think i should change knock sensors and switch back to regular gas??

first troubleshoot the reduced power issue ..

after that is repaired I would replace the knock sensors if indeed the dtc indicate this is defective...

fuel prices are going up to 4.oo for regular soon..

Ya it is very dangerous when this happens. seems to be a curse i think. had to go to Barrie about a month ago. truck ran perfect all through Toronto then once i got to 400 north ran into killer snow storm and of coarse truck started acting up. had hard time pulling off due to snow and almost got ran into couple times. Had trailer on to boot.

Thanks jCat. I will do. Think i should just replace throttle body?? Do whatever it takes. Use truck everyday for my business, can't afford to have it acting up. Expecially when i'm hauling my trailer.

The Throttle plate can get sticky from PCV/EGR gases, the control module can't mussel the throttle plate open.

See http://www.automotiveforums.com/vbulletin/showthread.php?t=968773

Caution - never open throttle plate by hand, have an assistant push the Gas pedal down with the key in the on pos.
Let the drive by wire system open the throttle plate for cleaning.

Don't use carb cleaners, the cleaner can strip protective coating, and damage seals on your throttle body.

I thought I had solved my reduced power problem with the cleaning and silicon grease on all plugins but it came back after a while. I replaced the throttle body and so far so good. My truck would run fine while on cruise control leading me to think it was the throttle position senser but it wound up being the throttle body. Thought I would pass this along, might help someone else. I bought a genuine AC Delco from Rock Auto for about $100.00 less than dealership wanted.