[Gmecm] Acquiring ECM schematic

[Webmaster at lotus-carlton.fsnet.co.uk]

It's just hard work. I'd suggest prinitng out my schematic, and some of those on Ludis's site. It's unlikely that there are very many different chips used in your ECM than in all the others. You'll find GM re-used known working circuits. The microprocessor section is likely to be identical. Where they re-used circuits, it's extremely likely that your ECM has exactly the same circuit diagram.

I was told the '8331 had everything, including the kitchen sink. Most of the circuitry is the same as on other ECM's. It's just the DIS/Ignition interface that's different. Oh - and the SFI stuff.

IAC valve is usually a 2 phase stepper motor. Is yours different? I know most European/Bosch systems use a kind of PWM driver.

Once you've decided basically what's going on, you have to sit down with a voltmeter set to 'ohms' or better still 'diode buzzer' and buzz out the connections between the individual components. Start with the power and ground connections, and then trace out the signal wiring. Boring and time consuming, but it's the only way I know.

Cheers,
Malcolm

-----Original Message-----
From:	Ryan Hess [SMTP:rgmecm at yahoo.com]
Sent:	16 June 2006 16:51
To:	gmecm at diy-efi.org
Subject:	RE: [Gmecm] Acquiring ECM schematic


Thanks much, Malcolm.  Now if Steve would just move it to the readable 
directory... :p

Now do you or anyone else have any suggestions on where to start with 
creating a schematic from an undocumented ECM?  I'm not familiar with 
the processes of going from a board to a schematic.   The ECM I have here 
(16132240) is extremely similar to the 8331, except that it uses some 
odd chip instead of an IAC driver.  Sequential V8, lots of I/O...  
Perhaps the biggest difference is it's cheap and in junkyards everywhere.  
Thanks,

Ryan