CN2 is the connector to the serial port on an OBD1 ECU. Here's the pinout of the Dataconnector IN a Honda ECU:

• 1: GND
• 2: RX (send Data from the PC to the ECU)
• 3: +5 Volt
• 4: TX (send Data from ECU to the PC)
• 5: N.C. (not connected)

This port is half-duplex (RX and TX are connected) in stock form. See OBD1 J12 for more information about full-duplex modification. A good pin header for CN2 is digikey part# 640456-4 Question From Web Geek_ "There are 3 search results for that part #, which is the right one?" For more information see this excellent post by Jim Truett: https://web.archive.org/web/http://forum.pgmfi.org/viewtopic.php?t=1663

Attachment:	Modify:	Size:	Date:	Who:	Comment:
CN2\_location.jpg	mod	13759	14 Apr 2004 - 00:19	tungsten2k	OBD1 CN2 Location