teamzr1 - let me try to understand....
PCM is a physical box comprising containing the "engine management computer"
ECU is a programmable chip soldered onto a board in the PCM
There's GM firmware (or whatever) in the ECU which runs the engine according to pre-set software parameters
Those parameters can be adjusted by plugging the PCM into a laptop equipped with suitable software
But if the GM firmware (or whatever) on the chip gets disrupted then either the entire PCM must be replaced or the ECU unsoldered and replaced (either permanently or by installing a socket)
Various questions,
1. What's the cost of a replacement PCM? Should it simply plug in and run the car properly? Or does it need to have settings adjusted?
2. What's the cost of a replacement ECU? Will it simply solder/plug in and run the car properly? Or does it need to have settings adjusted?
3. Once the PCM is replaced or repaired, will the car still have the same "engine management issue" it started out with?
3. Is the usual "fix" for this car's original problem (a) some mechanical work, or (b) adjusting the parameters in the PCM/ECU?
4. Is the suggestion here that the remapper trashed a good PCM, had it repaired into "plug and play" status and then trashed it again?
Whatever the rights and wrongs of previous interventions it seems to me the starting point is to get to the bottom of,
* What's needed to get this car running a.s.a.p,
* Where should that be done, and
* How much will it cost?
Although I can't answer any of those questions they are fundamental to finding a cost-effective way out of this situation.
Terms used can make it confusing, so let's define them
PCM is Powertrain Control Module, the calibration (Tune) is stored in a programmable flash memory
ECM is Engine Control Module, the calibration is stored in an E-prom chip
As to Corvettes, Pre-1994 used an ECM, 1994 to today a PCM is used
PCMs for a 1995 C4 as Mick has can be found as low as $150 US
Being Mick's 95 C4 is totally stock, then in most cases a used PCM for that year is a simple swap with the bad one
If the old PCM, someone with the knowledge and experience could un-solder the memory flash chip, put the into a flash chip
programmer device, they could reformat the flash chip and then flash in a stock 1995 GM calibration
Being the flash chip is surface mounted to the PCM board, the person doing the repair has to solder in a flash chip socket
as that way, the flash chip can be simply plugged in or out in the future
In Micks case, the problem was simple, the smog system, something was wrong, does not prevent the C4 from being driven, it simply
means every time is started the check engine light is on as smog error codes tripped
Not knowing why but instead of fixing the problem, they decided to go into the GM flash chip via some tuning tool and would take less than 2 minutes to turn off those smog error codes and also command so that the smog pump is not commanded on by the PCM
To do tuning ON-board, a tuning tool connects to the diagnostics port unto the dash which connects to the PCM like 1 network devices and moves data to and from tuning tool to the flash memory of PCM
Below I show a 1995 C4 and the few changes to do that
Not only is the calibration stored in the flash chip but also the operating system that the PCM computer uses
Somehow that shop when flashing in the changes corrupted the OS so now the PCM is dead
An example would be, you're copying a Microsoft Windows file to your computer and during the copy the power failed
now the original file is corrupted and MS Windows cannot function, so your P/C is hosed
What should be a simple tuning task, they screwed up
Here is the few error codes and AIR (SMOG) pump changes in tune was all that was needed to be done
I have been tuning since 1995 and have never hosed a PCM or ECM so that shop did something stupid or from lack of experience thought they
were making smog changes but instead changed something else, or their tuning tool is junk and crashed the PCM when moving the new tune on top of the existing PCM calibration
