I'm helping a guy try to get his '72 GMC, with a 2010 Camaro L99 to start and run right. I reworked the harness and he sent the ECM to Lt1swap to have the VATS removed. It starts but surges real bad. Initially it had an older style MAF, which I thought wasn't right, but since I have never had an L99, wasn't sure. The wiring had been spliced into the harness and not done very well, so I soldered the wires and didn't think much more about it. Well, as it turns out, that doesn't work. So he got the correct card style MAF, pigtail and the weld in mount from the GM dealer and hoped all would be good. He temporarily wired the MAF plug the same way the other plug was wired, but I'm not sure that is right, so I will be getting the pinouts for the plug tonight and will check them tomorrow. As is it throws a P0102 - MAF sensor circuit low frequency, and P0113 - IAT sensor circuit high voltage.

But the worst part is that the throttle doesn't work right. At times it will work, but once you go above around 75% throttle, it goes into limp mode and you have no throttle. Also, it will cut the fuel pump off. Does this sound right? I have never seen this happen on a GenIII, but not sure if it is a GenIV thing? If you wait a minute or two, tuirn the key back on and it comes back on and the throttle will work. The codes I am getting are P2119 - TAC throttle body range performance, P0122 - TPS circuit low voltage, P0223 - APP sensor 2 circuit high voltage, P2122 - APP sensor circuit 1 low voltage, P02127 APP sensor circuit low voltage. All of these make me think that there are wires crossed, but I wired the pedal color for color from the wires coming out of the ecm.

Anybody with any thoughts or suggestions? The owner of the truck I can tell is getting frustrated and starting to loose faith in EFI...

Thanks in advance for any input!

 

One other thing I should mention is tonight the throttle body started making a weird clicking noise when first keyed on, it never did this before. Is this a dying throttle body?

 

TB could be low battery.
Is the pedal from the same vehicle? If so, check the pinouts. I ran into something similar where A went to A, B weny to B, etc, except for 1 pair.

 

Its supposed to be from the same car, but then so was the MAF. I checked the part number and it is for a 10-14 Camaro. As far as the wiring goes, I just matched the colors of wires coming out of the ECM to the colors on the pedal pigtail. Going to do a continuity test and see what gives.

 

My TB clicked when I turned on the ignition. It always sounded like the butterfly closing completely. I never gave it any other thought.

 

you probably checked this but is the maf card pointing in the correct direction?

 

They all click when first keyed on, but this one would click like five times really quick.

Yes, it was in the right way. I rewired the MAF connector according to the pin outs I got from Mitchell on Demand at work, and the MAF codes went away.

As an update though, it turned out to be a bad throttle body. After checking all the wiring again, took the intake hose off the TB and manually tried to open the throttle blade. It opened but would only close about 2/3 of the way and then it would stick. Had to really force it closed, or turning the key on would do it. Apparently that's what was happening when driving, it would try to stick open, the ECM would force close it and then send it into limp mode, to avoid doing the "Toyota into a tree" thing. We took the TB off and then took the motor off of it, and the butterfly was smooth, also checked the motor and it worked smooth too. We put it back together and it works great now, so not sure if there was something floating around inside that fell out when we took it apart or not, but he is going to buy a new TB anyway just to be sure.

 

what about the pedal codes?

 

All the DBW pedal codes were due to the throttle body sticking.

 

I have an LS3 throttle body you can use to test with. Give me a call if you want to try it.

 

interesting...good to know, glad you got it sorted out

 

Thanks for the offer Bry, but its running fine since taking the TB apart and its not sticking anymore, so I'm 99.9% sure that was the problem, and knowing the guy that ownes the truc, he's already got a new TB coming if he isnt at the dealer right now!

 

Im glad too, but not nearly as much as the guy who owns the truck, he never came out and said anything, but I could tell he was getting pretty upset when it didnt run right. I told him from the start that it was going to start right up and be fine, guess thats what i get for being so overly confident, I havent had one fight me this bad in a while.

 

No worries. I'm just glad you figured it out and it's running well. I've been pimping the excellent driving qualities of these engines for years but most of my friends are still scared of them. I have a few who have taken the plunge since I did my first which makes me happy.

Hopefully we'll see each other at a show or two this summer. I'm planning on going to the Independence show a lot this year.