There is a very distinct family of ECUs found in 88-91ish OBD0 hondas. The main characteristics of this family:

• Oki80 C154 or Oki83 C154 MCUs that are essentially Intel8051 with a 12Mhz Clock Speed.
• Presence of oki 38256 EPROM on 90-91 models
• MPFI engines w/ 4 injectors
• non-vtec engines
• electronic advance distributors
• Presence of Oki6260 A IO controller chip
• Presence of NEC UPD7004 C ADC chip
• Presence of 5128 XRAM 2K SRAM chip

This architecture was also used by Rover in the UK, and appeared to do so for considerably longer than the 4 years this architecture was used in USDM and JDM cars.

A partial list of OBD0 ECUs:

• PG7 (88-89 Integra D16A1 - note the 86-87 version of this ECU ran the vacuum advance D16A1 motor. Different family)
• PM6 (USDM Civic/CRX Si - D16A6 SOHC)
• PM7 (JDM/EDM Civic/CRX Si - ZC DOHC)
• PM8 (USDM D15B? SOHC HF, EDM D16Z? ZC DOHC)
• PR4 (USDM 90-91 Int
• PR5 (JDM Integra ???)
• PP5 (UKDM Rover Cabio?)
• PS9 (USDM Civic Ex 4dr D16A6 auto???)
• PK2 (JDM Honda Prelude B20A Engine electronic advance)
• PH3 (JDM 86-89 Honda Accord B20A)

Understanding OBD0 Inter Chip Communication will be key to figuring out exactly how the ECUs work.

Attached below is an eagle (4.09) library containing the MCU (OKI 8xC154), RAM (M5128), ADC (µPD7004) and engine control counter IC (Oki6260 A) devices for using these components in eagle layout editor.

Attachment?:	Modify:	Size:	Date:	Who:	Comment:
pm6.lbr	mod	11725	05 Dec 2004 - 20:57	l3st4rd	eagle 4.09 library for some OBD0 ECU components