Types of GM ECM's

[John Spears]

 bruce plecan wrote:

 >As far as series types of ecm for GM;
>As I understand it there are C3, P4, and PCMs.  Is this true?

 Sort of.........I guess what you guys call "C3", I know it as GMCM. After
P4 is a P6 (92-93 LT1 and others), and then PCM's.


 >All the P4 use a memcal/calpak, use 27128/27256 proms, 
>and 3 connectors.

 Several P4's use two connectors. Also, don't forget the underhood P4's with
4 connectors.


 >What do the PCMs use?.

 There is also a P4 PCM that uses a 512 eprom. These are commonly found in
trucks in 93 - 94. This PCM has full transmission control in addition to
running the TBI engine (or CPI on the 4.3L), but still uses a regular
looking memcal with 512 prom.

 The flash PCM's have several configurations. The 94 - 97 LT1 PCM is called
a PCM66U. The name meaning that it has (2) P6 processors back to back and is
rated for Underhood use. Each board has a 010 flashrom. There are many other
configurations.

    John Spears




                 John Spears
Speartech Fuel Injection Systems
           www.speartech.com