94 ecm question
Thread Starter
Instructor
Joined: Jan 2004
Posts: 157
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From: marshfield ma
94 ecm question
I was told by a mechanic that i have to bring my car to a dealer to have the ecm programmed if i replace it because its obd2. I always thought you could just swap the ecm`s out and install the old chip in the new one. Can someone let me know which is right
Thanks
Thanks
Melting Slicks
Joined: Aug 1999
Posts: 2,240
Likes: 41
From: Baltimore, MD USA
Your PCM has a EEprom. Electrically Erasable Programmable read only memory. The EEprom is not on a socket.
The dealer reprograms the EEprom with the correct parameters used by your vehicle.
The older ECM/PCMs used Eproms (erasable programmable read only memory) which were on a socket. You use a special light to erase the data in the Eprom before you can reprogram it. The EEprom is erased electrically.
With the proper hardware (cable, computer) and software, you could program the PCM yourself. You would dump the contents of your EEprom and save it to disk.
Then using the proper software program to load the
data into your new PCM.
94 and 95 used a OBDII Diag. connector but are not OBDII compliant.
The dealer reprograms the EEprom with the correct parameters used by your vehicle.
The older ECM/PCMs used Eproms (erasable programmable read only memory) which were on a socket. You use a special light to erase the data in the Eprom before you can reprogram it. The EEprom is erased electrically.
With the proper hardware (cable, computer) and software, you could program the PCM yourself. You would dump the contents of your EEprom and save it to disk.
Then using the proper software program to load the
data into your new PCM.
94 and 95 used a OBDII Diag. connector but are not OBDII compliant.
Last edited by Hooked on Vettes; Oct 13, 2004 at 10:56 PM.
Le Mans Master
Joined: Jan 2003
Posts: 8,596
Likes: 19
From: Portland Oregon
Originally Posted by twkeough
I was told by a mechanic that i have to bring my car to a dealer to have the ecm programmed if i replace it because its obd2. I always thought you could just swap the ecm`s out and install the old chip in the new one. Can someone let me know which is right
Thanks
Thanks
He is somewhat correct. If you are replacing the PCM because of a failure of the original PCM, then yes you would have to take it to a facility that can flash that new replacement PCM with a GM calibration. You can of course purchase the software and hardware to edit your PCM programming, but I don't beleive that any of the hot rod software can flash a rebuilt or a new PCM with just a base calibration in it. That requires a GM SPS programming system or equivalent software and hardware. Some independent shops have these systems, I have one here at home as its part of my business, and of course all the dealers have it. And your PCM is an OBD1 system, OBD2 was introduced starting in model year 1996. 94/95 is OBD1. Some people say that the old prom style ECMs from 93 model year cars and earlier and some 95 and earlier trucks are OBD1 but its not really true. None of the older prom ECM had any true on board diagnostics such as the 94/95 flash programmable PCMs. Most people don't even know about the old acronym C3 or CCC or Computer Command Control, that is what it was called starting in late 1980. Jeez I am dating myself now.....
