problem with ETC/TAC (?)

[Till]

Hi,

as I mentioned in a previous thread ( http://www.efilive.com/forum/viewtopic.php?t=1712 ), I am installing an individual throttle body manifold in a C5 corvette. And I keep running into problems.

I got the car to start and run with a stable idle, turned of the engine, and got the "reduced power" message in the DIC. Error codes are P0606 and P1518. The service manual says that this means the PCM needs to be replaced. Well, I tried reading the PCM - didn't work. Writing a calibration - didn't work either. Rewriting everything - same thing. Took out the PCM, and hooked the PCM up to the OBD-II cable and a battery outside the car (with a special harness) - same problem.
Well, I got a new PCM, and everything was fine. I had programmed a 2001 OS into the old PCM, and I wondered if that may have been the reasons for the problems. I flashed my old 99 OS into the new PCM, just to be save.
Today the new PCM died. The engine hadn't even run today. We had just pushed the car to the lift. Again code P0606 and P1518.

I wonder what the reason might be. The cable going to the TPS had to be pulled a bit, so there may be a short somewhere. We worked on the TPS, so that may malfunction. But why was it fine after installing a new PCM?

With FlashScan, I made changes in the ETC tables. Those have a red symbol, and it only shows after the laptop was connected to the PCM. Are the changes to the ETC tables in the PCM, or in the TAC? Maybe the TAC malfunctions, and in some weird way takes out the PCM?

I am not sure what to do next. I have been told that there are plenty of problems with the TAC in older C5s, and that the error messages are sometimes incorrect. Maybe I should get a new TAC in any case.

Does anyone know where I could get a PCM? In Germany you can only buy it in exchange for a broken PCM, you can't just buy one to keep it in stock.

Till

[Till]

Maybe the problem is related to this:


Date:
May 30, 2005

Description:
Changing the ETC tables too far from stock may cause the ETC system into limp mode. A TAC (Throttle Actuator Controller) communications failed DTC will be set.

The TAC module stores a sane ETC table. If the PCM commands a value too far from the TAC sane value then the TAC logs a comms fault. Too many comms faults and the PCM will go into limp mode. How far from stock your ETC tables have been changed, determines how quickly a comms DTC can be set.

Status:
No fix available.
EFILive does not have access to the TAC module and cannot change the calibrations stored in it.

Workaround:
Restore your factory ETC settings.


This wouldn't really explain why the PCM can't be rewritten though, or does it?

Till

[wait4me]

You can send me the computers, i can check them out and fix them for you for free....
If you are worried about voltage draw and thinking that is the culprit, maybe make a different 5 volt reference from another source besides the pcm for the draw... ?? Same with the 12 volt outputs, As long as they are accurrate voltages, the pcm wouldnt know the difference.

[Blacky]

This wouldn't really explain why the PCM can't be rewritten though, or does it?
Till

The comms DTC P1518 does not cause the PCM to not be able to be reflashed. The P0606 is set when the PCM has detected an internal fault (such as a checksum failure or inconsistent ETC tables) and locks itself from being reprogrammed.

Which version of EFILive are you using?

Do you have a stock PCM *.tun file from your vehicle? And do you have the most recent *.tun file that you flashed in?
Please send them both to me at paul@efilive.com.

Regards
Paul

[Till]

The P0606 is set when the PCM has detected an internal fault (such as a checksum failure or inconsistent ETC tables) and locks itself from being reprogrammed.
I didn't know that. I would have expected a check sum error would be reported immediately. Maybe it doesn't like something about my ETC tables, and there is a counter for the number of times it ignores the problem until it shuts down (?).

I use version V7.2.2 (Build 227).

I am looking at the last calibration, but it doesn't show the ETC tables. For some reason those only show after the computer was connected to the car.
Potentially bad things I did (from recollection):
- I reduced maximum throttle position in idle to 3.? %.
- There are two tables with maximum and minimum throttle postion for some power or air flow, I don't remember exactly. I set the minimum tables to zeros. (Maybe I should have just recuced that to very small values)

This is all related to the manifold flowing so much air. If the throttle opens by 20% (I think that is stock) when the car hasn't learned idle yet, the engine just hits the rev limiter and goes into reduced power mode. So you have to reduce the max throttle at idle.
I never really understood what IAC does with ETC. Changing default park position and maximum IAC steps didn't seem to make a difference to the revving up when starting the car.

Since there is no MAF, I set the whole MAF table to zero. Could that be a problem?

Paul, I will send you the .tun files.

Till

[SinisterSS]

Till, have you calibrated your VE table? That will help with idle issues.

[Till]

The VE table is calibrated pretty well, at least for low rpm and load. The problem is not stalling or flaring. Befor the idle is learned, the PCM will open the throttle to some value. It might be the maximum idle contribution in the ETC tables. With the regular intake and throttle body, this just gives you raised idle for 2 or 3 seconds. With the ITB intake, this gives the engine enough air to hit the rev limiter! :shock:
That is why I changed the maximum idle contribution. And I changed it to a pretty small number, since that seemed to work quite well. Maybe this caused the PCM to think something is wrong, issue code 0606 and lock down.

Till