i'm trying to help someone out by flashing a base tune into a '94-'95 ecm, then shipping it to them. since i don't have a benchtop setup, the only means i have of doing this is by physically connecting his ECM to my car.

he has shipped me 2 ECMs, and both have problems. if it were just one i'd be very tempted to blame the ECM and call it a day. both ECMs have the exact same problems/symptoms, so i'm really puzzled.

i've tried maybe 20 times to either read or program these. once, only once, i successfully read one of them. all other times tunercat reports a communication error after the fans kick on/off. iirc, the error when trying to program is "incorrect return code." in all error cases the ECM then resets fine and appears to control systems properly.

i've used this same car, cable, laptop, and software to program my ECM and a few others for other people and never had a single problem. even after all the problems with these two, i hooked my ECM back up and was immediately able to read and program it.

one thing i did notice, looking at the one successful read, the flash on that ECM is for an f-body. is there anything specific about how the f-body flash works that communicating through the vette ccm would impede? i ask that because my datamaster wouldn't ever connect to my ECM until i selected to "disable ccm handshake."

lastly, both the modules to appear to work. freescan can connect and the real-time data appears correct. they're both able to start my car for an instant (but it won't stay running due to the big discrepancy between stock and my engine/injectors).

any help/input appreciated, thanks!

-michael

 

Michael; An PCM with an F body program (tune) will cause communications problems when installed in a Y body, since the F body program has no knowledge of the CCM and ASR computers. You should see several DTC codes related to communications problems, off hand I don't remember the specifics.

In addition, the VATS handshake protocol won't work and the car may start, but only run for a few seconds, as you discovered.

If you electrically isolate the PCM from the serial bus (ADLC), and connect your PC/cable adapter serial data, directly to the PCM serial port, you will then be able to program it.

Mark

 

aha, so it really is that simple! looks like i need a benchtop setup.

thanks.

-michael

 

I was able to perform such a flash by unplugging the CCM.

Not very practical unless you happen to already have your dash out of the car...

 

those of you who have assembled a benchtop setup, is this correct?

Ground: Blue1, Gray32, Red18, Red2, Pin1 on Serial
+12V: Black15, Black30, Black31, Blue3
Data: (Pin5 on Serial) Blue30

i ask because i've seen pics of benchtop harnesses that appeared to have only a single ECM connector, but the above info says all 4 connectors would be necessary. (i'm going to solder pin leads so i don't need the connectors anyhow, just trying to make sure i have the pin numbers right.)

thanks!

-michael

 

Since you've seen them with only one connector, I assume that is the Blue connector. So try using only the power and ground and data lines on the blue connector and see if you can download the bin fine.

It makes sense that they would only require one connector for programming - it would be a PITA to have to connect and disconnect all 4 on the assembly line.

If you want to be perfectly safe, since it's an unknown, then connect all powers and grounds as you have identified. But if I could get several reliable reads using just the blue connector I'd have no qualms about flashing like that.

 

that sounds like a good plan. i'll report back.

thanks.

-michael

 

FWIW-

Unless you have a real schematic of the PCM I'd follow AKM's advice: http://www.akmcables.com/techinfo.htm

Or at least hook up all the ground pins, so the PS by-passes all work. Me, I worry about RFI and
such when working on low-current components. That's based on my experience with the ECM
emulator I've used for the last couple of years on software development...
http://www.thirdgen.org/techboard/at...ench-09lcc.jpg

Good luck.
DrJ

 

i realized it would be more work to go back and add pins, so i went ahead and did all 4 ground and 4 +12V listed above. this worked like a charm. the hardest part was figuring out the data and ground pin on the d-sub of my cable, it doesn't match AKM's info.

-michael