A collection of information about OBD2

• SAE J1850: describes the network hardware, the electrical specification, basic protocol, and CRC byte
• SAE J2178 part 1: describes the 2 types of packet headers and typical physical node address assignments
• SAE J2178 part 2: describes the standard data to be exchanged on the network, including scaling, ranges, and transfer functions
• SAE J2178 part 4: describes the message assignments for the three byte form of the consolidated header format.
• SAE J2190: describes the phyically addressed messages used for diagnostics, trouble codes, freeze frame data, and reflashing.

• 4Mbit/512KByte Intel flash chip used in some OBD2 PCMs
• ELM 322 single chip VPW <-> RS232 converter from Elm Electronics
• MC68332 processor used in more recent OBD2 PCMs
• MC68HC58 VPW interface chip used in some OBD2 PCMs.
• BDLC (Byte Data Link Controller), a VPW interface embedded in some Motorola microcontrollers
• M68HC12B a 68HC12 microcontroller that includes a BDLC
• HIP7010 byte level interface from Harris/Intersil, now sold to AMI Semiconductor, may be obsolete
• HIP7020 J1850 line transceiver from Harris/Intersil, now sold to AMI Semiconductor, may be obsolete
• AU5783 J1850 line transceiver from Phillips.
• L5951 J1850 line transceiver plus triple integrated regulator (3v3, 5v0, 7v8) from ST

• Whitepaper from Intel about the j1850 electrical specification.
• App note AN1212 from Motorola about J1850 communications
• App note AN1731 from Motorola, schematics and code for a simple OBD2 scan tool
• Engineering bulletin 601 from Motorola, initializing the BDLC
• Flash socket from Yamaichi, low profile ZIF

• An OBD2 chat forum
• AKM electronics has some OBD2 info
• A site for GM OBD2 PCMs