Do I need a new TB?

[Kidder]

So twice now in the last three weeks i have been driving my '05 silverado 2500HD and caught the "Reduced Engine Power" message on my display. This throws my SES light and puts me in "limp mode" allowing me to go at a top speed of 20mph. I was in the city both times and pulled over right away and shut it down. The first time I had just pumped gas so I thought maybe I didn't have the cap on tight enough and it threw something in my emissions control. Took gas cap off put cap on start engine and it runs fine but SES light stays on. Restart later that day and the light is gone and still running fine. A couple weeks go by with no issues now im driving home from work and it does the exact same thing. Pull over shut it down and wait a minute, restart engine and no problems. Light is on at this point. Restart later that day and light is gone and running normal. The next day I did an oil change, changed the air filter, cleaned the maf sensor and cleaned the throttle body. This is the Drive By Wire system so I checked all the wires at my plug to the throttle body none of which are loose or corroded and there are no breaks in any of the wires from what I can tell. All was well until this morning it happened again so I got it out of limp mode and went to a buddys house and scanned it with the SES light still on and got P1516 TAC module failure. I know this TB is original equipment and didn't look like it had ever been cleaned at all. 212,xxx miles and there was a good bit of build up in the TB. Anybody ever had this happen before? Anybody know a common fix? I've done some searching and am pretty sure I'll end up needing a new TB but wanted to hear it from you guys before I take the plunge on it. This is the 6.0L but I have heard of the same symptoms on a lot of the other engine models as well. Sorry for the novel, just hoping for help.

[fox_racin4]

Get the truck to a shop WHILE in limp mode May take awhile but thats the only time you can really scan it. Also it needs to be a good scanner not a cheap 50$ scanner that gives you a code to go and google.

[Lbox88]

YOUR VEC. HAC ELECTRONIC THROTTLE BODY UNIT SO IT USES VOLTAGE SIGNALS TO CONTROL THROLLTE BLADE IN THE THROTTLE BODY. WHAT I HAVE SEEN ON THE JOB IS A FEW DIFFERENT ISSUES THAT CAN CAUSE THIS PROBLEM.

FIRST OFF THERE IS A UPDATE FOR THE PCM TO ADDRESS THOSE CODES, BUT YOU WILL HAVE TO TAKE IT TO THE DEALER FOR THAT.

SECOND THERE IS ISSUES WITH THE ACTUATOR ON THE THROTTLE BODY BINDING UP AND CAUSING THE CODES.

THIRD THERE IS A YELLOW WIRE COMING OFF THE THOTTLE BODY CONNECTOR THAT BREAKS INSIDE INTERNALLY AND CANNOT BE SEEN TO THE NAKED EYE. THE BEST WAY TO TEST THAT IS TO GRAB THE WIRE ABOUT 5 INCHS FROM THE CONNECTOR AND TUG IF IT FEELS SPONGY OR BREAKS THATS YOUR PROBLEM.

FOURTH THERE IS A GROUND AT THE BACK OF THE PASS. SIDE HEAD THAT BECOMES LOOSE. WHEN I GET ONE OF THESE VEC.S IN MY SHOP I UPDATE THE PCM REPLACE THE THROTTLE BODY UNIT AND CONNECTOR TO IT AND CHECK THE GROUND ON THE BACK OF THE HEAD IF I DON'T DO ALL OF THIS THAT BITCH SEEMS TO ALWAYS COME BACK. GOOD LUCK

I found this, try all those?

[Kidder]

Get the truck to a shop WHILE in limp mode May take awhile but thats the only time you can really scan it. Also it needs to be a good scanner not a cheap 50$ scanner that gives you a code to go and google.

The scanner I used pulled the code and told me the problem right on the screen, no need to google anything. I pulled it the second time it happened as a saved code without the light being on, and I pulled it again this morning with the SES light on. Both times the same exact code and also the only code stored or being thrown.

YOUR VEC. HAC ELECTRONIC THROTTLE BODY UNIT SO IT USES VOLTAGE SIGNALS TO CONTROL THROLLTE BLADE IN THE THROTTLE BODY. WHAT I HAVE SEEN ON THE JOB IS A FEW DIFFERENT ISSUES THAT CAN CAUSE THIS PROBLEM.

FIRST OFF THERE IS A UPDATE FOR THE PCM TO ADDRESS THOSE CODES, BUT YOU WILL HAVE TO TAKE IT TO THE DEALER FOR THAT.

SECOND THERE IS ISSUES WITH THE ACTUATOR ON THE THROTTLE BODY BINDING UP AND CAUSING THE CODES.

THIRD THERE IS A YELLOW WIRE COMING OFF THE THOTTLE BODY CONNECTOR THAT BREAKS INSIDE INTERNALLY AND CANNOT BE SEEN TO THE NAKED EYE. THE BEST WAY TO TEST THAT IS TO GRAB THE WIRE ABOUT 5 INCHS FROM THE CONNECTOR AND TUG IF IT FEELS SPONGY OR BREAKS THATS YOUR PROBLEM.

FOURTH THERE IS A GROUND AT THE BACK OF THE PASS. SIDE HEAD THAT BECOMES LOOSE. WHEN I GET ONE OF THESE VEC.S IN MY SHOP I UPDATE THE PCM REPLACE THE THROTTLE BODY UNIT AND CONNECTOR TO IT AND CHECK THE GROUND ON THE BACK OF THE HEAD IF I DON'T DO ALL OF THIS THAT BITCH SEEMS TO ALWAYS COME BACK. GOOD LUCK

I found this, try all those?

First step: haven't done that.

Second step: Only thing I've done to the throttle body itself is clean the hell out of it. I suppose new throttle body would eliminate this problem?

Third step: I completely disassembled the wiring and took each wire out of the pigtail one by one (so I wouldn't mix up location) and checked for breaks/corrosion and did the "tug test" All seemed to be well but to be sure I cleaned them while I was in there.

Fourth: I checked G103 and G104 with no luck on that. Grounds appear to be in tact and not corroded/frayed/broken/loose.

I think maybe I'm on to just breaking down and buying the throttle body itself and taking it to the stealership for those PCM updates. Thanks for the help so far guys. Great to have somebody to bounce ideas off of.

[deathcards]

i say pcm update first might save some cash if thats the last problem

[Kidder]

Throttle body should be here tomorrow or Thursday. Decided I'm going to do both the throttle body and pcm updates. I want my carbureted K5 blazer back..

[Kidder]

It's been a couple weeks now since I installed the new TB and so far no issues. Haven't found the time to do PCM updates yet. Hopefully this weekend. Thanks for the help fellas.

[inferno1985]

i was going to say cleaning the throttle body from only 1 side isnt going to do anything. was going to tell you to take the whole throttle body off and blast it with tb cleaner and use a toothbrush to clean it untill it sparkles like new. but seeing as you bought one, hopefully it fixed the problem.. im not a expert but why would the pcm have any effect on a drive by wire system?

[Mustang06331]

The only time I have experiences this reduced engine power" limp mode " is if the thermostat was stuck open and not allowing the motor to rise to operating temp . Most don't know this but it is just as detrimental to run under temp as it is to run over temp . Clearances in modern engines are so tight running below op temp wears them fast . Don't believe me check the suggested oil weight of most modern engines , most take 0-20w full synthetic for purposes of squeezing every last drop of power by losing paristic loss created by heavier weight oils .