Lil'John

In an effort to use the speedometer output of the PCM, I had been changing some of the settings to sync up the PCM and the speedometer.

I think in the process I may have bricked two PCMs now

On the first one, I had the laptop crash in the middle of the flashing... but I think I was able to recover it. I was able to run the engine after the recovery but on the next flashing, the PCM died.

I ordered a second PCM and again tried to flash it with the same tune. The results are the same.

I am using the Jet DST... I know... worst POS ever. I really wish I never wasted my money on it

The engine is a 2004 LQ4 from a Silverado 2500HD.

The symptoms are this:
1) The fuel pump relay "pulses". I can't think of a better description. It sounds like it is getting shut on and off VERY rapidly.
2) I can't read ANY information from the PCM. Whether it is to read the program on the PCM or generic PCM information.

I was tinkering with two settings:
1) Speedometer Input Pulses Per Revolution
2) Speedometer Input Pulses Per Mile

The original tune I was supplied had pulses per rev as 40 and pulse per mile as 4,000. I modified these to 16 and 8.

The documentation I have did not show a link between these two.

Before I go fry a third computer or decide to just set the car on fire, any input would be GREATLY appreciated.

Frost

iTrader: (45)

Yes you can tank the GenIII's with an out of range value in this area.

Lil'John

That makes sense... but according to the "help" information from Jet:
Speedometer input pulses per revolution, min of 0, max of 256
Speedometer input pulses per mile, min of 0, max of 255996

If the above is actually correct, my values fall in a valid range. But as I mentioned, nothing in Jet's documentation show any link between the two

foff667

iTrader: (2)

Those are just the upper & lower limits of what the creator of the software has deemed valid, our software also has these, but it adds a warning "do not set to a low number or zero as the pcm may become unstable" or something to that affect.

There are dozen's of tables that can fry the pcm if you set the values to odd values such as the min or max value not to mention to simply doing weird things if you do the same.

Lil'John

So what probably killed the PCMs is the 8 pulses per mile setting that I did from 4,000.

I'm assuming that I'm out of luck in trying to recover these PCMs. From a previous thread I was told to try 15 minutes of leaving power off as well as MUCH longer. I tried both with the first dead PCM both ~15 minute times as well as over a week with no luck.

Frost

iTrader: (45)

They can be repaired, but they can be replaced so cheaply, it's rarely worth it.

You need a valid binary with the same byte-order that your hardware programmer will use (not the same as you would get reading one out in a traditional method). Then, the SMD flash chip has to come off and be written with a bench programmer and re-installed onto the board.

01ssreda4

iTrader: (96)

Wow, what a pain in the ***.

TunerGuy

Try using the PCM Recovery on the tools menu of Jet Flash, but make sure you're using a good file, switch the values back to stock. JEt isn't that bad of a program, it just doesn't get the support, that the rest of them get. If you're dtill having trouble go to the monodax forum, its where the TC and Jet guys hang out

Lil'John

In your experience, what should a PCM(blue green from 2004 Silverado: SERV#: 12586242) normally go for? What does the repair normally go for?

The other issue is that each new PCM eats a license off the tuner... so that takes another $100... granted, I'll burn the POS before I inflict it on someone else so it is a minor issue.

The whole project has been that way. If it can go wrong, it has It has been so bad that I had a badly machined input gear on my rebuilt transmission that made a LOT of noise but not visibly noticeable until you looked REAL close.

Even doing the engine install was an issue and that was the easy part.

Lil'John

I actually did try that using the stock tune of the PCM. It can't read the PCM at all.

And you are right... Jet really isn't "that" bad of a program... just frustrating to be close to daily drivable and frying PCMs trying to get the speedo working

wait4me

iTrader: (10)

Send them to me, ill fix them. 15 bucks each, and 13 for return shipping.

Your ecm is stuck in a infinate reset loop. Causing the system restarts in the os. Hence why you hear the fuel pump output pulsing at 60HZ.

Those tables arent really good to be messing with. Just set the values to what your tire and gear ratio are and leave them be...

TunerGuy

You're the answer man

The OP has a 8K pulse aftermarket speedometer he is trying to drive with the PCM, which is the reason, he tried changing the settings, and didn't toally understand their purpose

Lil'John

Thank you VERY much for the offer and explanation.

Thank you for the better description of what I'm trying to do. And you are correct that I didn't understand the purpose of the settings.