Hey guys. The day before my trip to ECS for diagnostics and tuning, I get the famous Reduced Engine Power message AGAIN. I've been plagued by this for over a year now. And its been fine for a couple months. I'm about ready to sell this damn car cuz it's proving to be not worth the trouble. So, to my point, I'm getting the following codes:
PCM:
P1120 HC
P1220 HC
P1516 HC

TCS:
1278 HC (I know this one is because of the PCM, so no need to diagnose this one)

RFA:
C2120 HC

I know its short notice but I need help. Thanks a lot guys.

 

What mods do you have done to the car?

 

I can't be 100% sure of what is done to the car other than what the previous owner (who also installed the parts) told me. but here's what I think I know haha.

Lunati Voodoo 228/232 Cam
LS6 TB/MAF
Vararam Intake
Kooks LTs
B&B Bullets
RAM Clutch

P.S. Is there any way I can talk to you on the phone Doug? I'm supposed to bring the car up tomorrow (4 hour trip) and I'm hoping there's something I can do today that may help. I'll take the chance and drive it up while in REP mode but it'll take FOREVER. I'm running out of options with this car.

 

UPDATE: I was able to get the car running right by clearing the DTC's while it was running. So I should be able to get the car up to ECS. Does anyone know any problems that could be caused by doing so?

Also, the first time I started the car this morning (it has sat for a week) it went into R.E.P mode. After I cleared the codes it started running right. So I drove it up the rode a little ways, no REP mode or Service TCS messages. I stopped on the side of the rode and revved the car a little, maybe up to 4K and it dropped right back into REP. :-/ I don't know what to do about this damn thing.

 

I am out of the office today, (I'm actually at my daughters soccer game and keeping myself occupied..) but the only thing I could do either way is offer advice to get it here. It could be in the tune, so if you do not have software there's not much that's going to help you there, or there could be an issue with the throttle body etc.

You can clear the codes "on the fly" if it's intermittent by holding
the options button down with your thumb, and hitting the fuel button four times. The car will display the codes, then hit reset. It will then show the number of codes, at that point hold the reset button down to clear them, and the E/M button to get out of that mode.

Also check the wiring around the throttle body for and chaffed or pulled wires, loose connections and so on. Other then that I'm sorry to say that we would have to have the car here to diagnose it.

I hope it works out ok for you to get it here!!

 

Most of these codes are throttle body related--and they are OLD codes (HC) mean history codes--
The usual suspect is the TB pigtail that is not connected well or fouled--could be wet or greasy--
However the most common TB code is the P1514 whwich can be tuned out by adjusting the "predicted airflow table" this goes out of range with major mods like hds/cam/hdrs
Here is a link to code p1516 --go thru the diagnostics http://www.gearchatter.com/viewpost14490.php see if it helps

 

You're half right. H=history C=current.

 

I'm just gonna take a huge chance and try to make it up to ECS. I'll leave a list in the car with the current codes I've been getting. It'll make it that much easier to diagnose the problem there. Thanks for your help guys. Wish me luck :-/

 

Well guys, bad news (yes, more). After a whole fiasco with east coast supercharging (the details of which I will not get into), the car is still not fixed. It went into Reduced Engine Power in their parking lot the day i picked it up and after it was supposedly fixed. It left me stranded over an hour from my house the other day and I've lost all hope in getting this car to run right. I'm still getting the same codes.
PCM
p1120hc, p1220hc, and p1516hc. P1515hc pops up every few times I try to delete the codes.
I've taken the tb connections apart and cleaned them. Packed them with dielectric grease also. No difference.
Also, my ac still has a no comm on it. ECS said they had fixed that also. I just installed new hvac controls and still have the same issue.
Can anyone help me out? Thank you very much.

 

Please. Anyone. My car can't be the first and only one to do this. Any ideas from the people who have run into this before?

 

You clearly have some serious electrical issue's. I personally had a lot of drive time on that car, and everything was flawless at that time.

You also went long stretches without any issue's before bringing the vehicle to us, so you should understand that. I hope you get the car repaired, it's not going to be an easy one.

 

These electrical gremlins can be a nightmare and not always easy to diagnose. They also can be very intermittent so it would not surprise me in the least bit that ECS could have driven the car with no problems. My last car did this and it took about 2 or 3 visits to a dealer (befere going to ECS) to troubleshoot. I got lucky in that ECS was able to find a chaffed wiring harness that I believe lead to my problem on my current car. My last car had a similar problem that ECS also helped with.

What are your A/C controls doing? The reason I ask is when my last car had the electrical problem I also loss control of which vents my A/C was using. Turned out that the vacuum line had been damaged presumably by a battery leak (also very common) that also damaged the wiring harness that caused the engine issues. Was fixed by ECS and never had a problem again. Just to be safe and because its easy enough, take a look around and under your battery for signs of a leak. Is it the orignal battery? My last car had a new battery when I bought it used but it was obvious the previous one had leaked.

This is a longshot but easy to check. Look at the electrical connections inside the accordian covers in the door jam. Very common for one of the wires to become exposed. Causes some wacky DIC messages. Matter of fact just about everybody who checks them, problems or not, finds them exposed. You can seal them with liquid electical tape.

Did you check your grounds? Also common for them to get corroded. Bill Curlee has a great post on diagnosing and cleaning them.

Good luck.

 

I'm in no way doubting ECS or their ability to fix my car. I know electrical issues can be a ****, and the car drives fine for a month and then goes nuts, conveniently when I'm over an hour from my house. So that post was not meant to bash ECS. They replaced one of the batter terminal bolts, which was causing a loose connection, and I was told that they cleaned the grounds. But upon looking over them, I noticed that they looked the same from the last time I had messed with them. I'm not genius, but I don't think contact cleaner can make rust disappear.

Concerning the ac, when I would hit the ac button, the light would either blink for a few seconds and go out, or the light would stay on without blinking, also for a few seconds. The compressor would not turn on, now would the little snowflake emblem show up. The lights were very dim also. I had a ruptured refrigerant line, Which they replaced. They resoldered the connections on the control board. And the day I picked the car up, the ac worked. But when I went to turn it back on about an hour after picking it up, the same thing would happen. No ac. Blinking light for a few seconds and then nothing.

 

No worries man. I didn't read your post as a bash - was just explaining that I went thru a similar issue on two separate C5s. On my last car, I was just fortunate that ECS was able to figure it out when the Chevy dealer couldn't after 3 attempts. My last car with the damaged wiring harness would not only throw codes but would start misfiring too - and it only happened in the rain so I figured it had to be electrical.

Yeah your A/C issues sounds way different than mine. I have no further guesses on that one. Check those connections in the door jam. Again, its a long shot, but mine was causing some real bizzare DIC messages. Plus it only takes about 5 minutes and chances are your wire on that connection is already exposed.

 

did you try checking the AC pressure? mine had a leak and when the pressure was too low, the little light on the ac button blinked and it wouldnt turn on. as soon as (thought i fixed the leak) i recharged it, i had no issues until it leaked out again

 

Well guys...As of yesterday afternoon, my car was running perfectly. I swapped the throttle body for another ls6 unit (and drilled a 1/8in hole in the butterfly) and the car started right up, CEL went off, and ran perfectly. All the codes it had been throwing are now H's, or gone completely . Thanks a lot for everyones help. Hopefully she'll continue to run well.

 

So it was the TB the whole time? Aint that some shyt.Glad you got it running.

 

Shouldn't be drilling the throttle blade.........

^^^ This would have me extremely, cautiously, optimistic. Judging by the history of the problem, you may not really know if it's fixed for another month or two.

 

Well the original tb was drilled. And I've read a few threads on here talking about it being beneficial to big cammed cars. So I said f it and went with it. Haha. But really I'm hoping this is it. The car is still on double secret probation. So hopefully it'll prove itself worthy. Or maybe it'll run well enough and long enough for me to trade it on a Z06 haha

 

Hey guys. I know everyone is getting sick of this thread and wants a resolution to this REP problem with which I've been plagued. So here's an update. After my TB install, the car ran great for two 40+ mile drives and I thought it was all said and done. But, feeling confident, I drove the car to the home I recently purchased (to find its spot nestled in the garage) and it ran fine...until I got within about 5 miles of my house, and it dropped back into REP. Naturally, I was cussing the car and I think I might've even punched the dash. Since then, the car has not come out of REP. I have checked and cleaned all grounds on the car, went through most of the wiring as best I could, checked, cleaned, and applied dialectric grease to the connections under the hood, and even replaced the TAC module this afternoon. None of these actions have produced any results. There has been no change. The car is still in REP, I'm pulling the same three codes I had before: P1516HC, P1120HC, and P1220HC. I'm officially out of options guys...I don't know where to turn at this point, other than lighting it on fire, rolling it down a big hill and calling the insurance company (after 15 minutes or so, just to enjoy the flames). Am I looking at some time at the Stealership?

Also, the AC still is not working. The system was recharged by ECS (who also repaired, and then replaced, my hvac controls. I'm also out of option with that one...
P.S. This whole ordeal has me questioning my faith in the Corvette name...