• Got the Contributing Memberships stuff finally worked out and made up a thread as a sort of "How-To" to help people figure out how to participate. So if you need help figuring it out, here's the thread you need to take a look at -> http://www.corvetteflorida.com/forums/showthread.php?t=3581 Thank you, everyone! Rich Z.

Reduced engine power still

V

vetteguy61

New member
Hope there is an electrical wizard here to guide me as to what is causing my LS1 383 stroker to go into reduced engine power when I start first thing in the morning or when I shut it off for a short period. The DIC shows the following codes each time it happens, P1120, P1220, TC 1228 and U1000 and U1064. The throttle body has been replaced, Pedal Assembly replaced, all grounds cleaned, wire harness checked for breaks,all connectors checked and cleaned.
Do I possibly have a bad TAC module, or could it be the PCM. Sure need some help on this if possible. Been going on for a year now and no one can pin point the problem.
 
Jeez Mike, I was hoping this got straightened out by now. The guy working on it couldn't find the problem?

Probably getting pretty old by now just swapping out parts and finding that they don't fix the problem.

I can't really think of many people to recommend you go to, unfortunately. About the only one who comes to mind might be a guy named Shane, who is the Corvette tech at Champion Chevrolet here in Tallahassee. He's been working on vettes for years now with that dealership and is pretty darn good with them. Champion Chevy hasn't been averse to taking in modified cars for Shane to work on, so it might be worth a shot.

I wonder how many other cars (besides yours and mine) that Chris Harwood has worked on that are still having problems?
 
I wonder how many other cars (besides yours and mine) that Chris Harwood has worked on that are still having problems?

?All of them?
:shrug01:
 
C5 pcm tables are not compatible with an ls3 throttle body.
The pcm has to get new tables and lots of tuning to make it work.
 
Curacao said:
C5 pcm tables are not compatible with an ls3 throttle body.
The pcm has to get new tables and lots of tuning to make it work.
Click to expand...

Hmm, well that's interesting to know. Does that also apply to the '09 LS7 throttle body that is on my engine in my C5Z?
 
Curacao said:
I'll check and let you know.
Click to expand...

Thank you. I'll need to let the tuner who will be working on my car about this if that is the case. I'm not going to let anything to chance assuming that he does know about this.
 
One other note here, but I would presume that if the PCM tables are all screwed up concerning the measured air flow and throttle blade position of the throttle body in relation to what the TAC module is expecting to see, why yes, I would think that certainly could put the car into reduced power mode as the TAC module would think that the throttle body had failed and then put the car into failsafe mode. With a drive by wire system, there HAS to be safeguards programmed in to keep the car from going out of control because of a failed throttle body circuit causing the blade to go wide open unexpectedly.
 
Ok, here's the problem the gold/brass (09 and newer) colored blade throttle body is the problem, it opens the opposite way as the aluminum/silver blade unit.
 
My car had a complete new EFI tune put in and ran just fine for 2 months when it started going intermittent reduced power. Sometimes while I'm driving and sometimes when I first start it up.It will run fine for a week or two then act up again.
 
Gerg at Antivenom build a LSX454 for my friend and I did all the breakin and it had no problems. When I started doing some wide open throttle runs then it started to give me error codes, also at some startups the tac unit will do a test on the blade and sees there is a problem. Greg has solved the problem. Now I get to drive the beast :reddevil: for fun.
 
Curacao said:
Gerg at Antivenom build a LSX454 for my friend and I did all the breakin and it had no problems. When I started doing some wide open throttle runs then it started to give me error codes, also at some startups the tac unit will do a test on the blade and sees there is a problem. Greg has solved the problem. Now I get to drive the beast :reddevil: for fun.
Click to expand...

Is there any info about this online? I'd be curious to read more about it as I believe I have the gold colored blade '09 throttle body on my C5Z engine. Logically I'm trying to figure out why the direction of the blade opening would make any difference. The TB throttle position sensor only returns a voltage to the TAC module and PCM which is proportional to the amount of travel that the blade makes. All that matters is how much air is the throttle body allowing to pass through it via the position of this blade, which is referenced by the voltage the sensor emits. The actual amount of air passing through the throttle body is measured by a voltage emitted by the Mass Air Flow sensor further upstream. As long as all of those voltages are still proportional to the relevant values they are supposed to represent, I can't see the direction of that TB blade really being much of an issue. That is, unless the blade itself meets a physical obstruction because the intake itself won't accommodate that direction of travel.

Greg still has an account here, so can you ask him to stop on by and explain this to us?
 
That DOES suck Rich, but at least you're finding and correcting things that are just
plain wrong and should never have happened in the first place. Plus..........it's very good
reading for anyone with a C5. I'm learning a bunch about my Vette just from reading
this thread. This is a SERIOUS "good news/bad news" thread, in that the good news is
you're finding and correcting problems, while the bad news is it's costing you more time
and $$$ to make it right! At least the light at the end of the tunnel is getting a bit brighter. :thumbsup:
Andy :wavey:
 
Yeah, someone on CorvetteForum told me about this problem a while back, but I completely missed the significance of it.

http://forums.corvetteforum.com/1578796758-post629.html

Heck, I think at that time I was still trusting Aaron at his word and expertise.

Well, looks like Mike and I both need to be scrounging up a compatible throttle body for our cars.
 
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