The OBD0 MPFI ECU family, utilized in 1988–1991 Honda and Acura vehicles, is defined by a specific hardware architecture centered around the Intel 8051-based microcontroller.

Hardware Specifications#

The primary characteristics of this ECU family include:

• MCU: Oki 80C154 or Oki 83C154 (Intel 8051-based, 12 MHz clock speed).
• EPROM: Oki 38256 (found on 1990–1991 models).
• SRAM: 5128 XRAM (2K).
• I/O Controller: Oki 6260A.
• ADC: NEC UPD7004C.
• Engine Management: MPFI (4-injector), non-VTEC, electronic advance ignition.

Note

This architecture was also utilized by Rover in the UK for a significantly longer production cycle than the four-year window observed in USDM and JDM markets.

ECU Identification List#

The following ECUs utilize the OBD0 MPFI architecture:

• PG7: 1988–1989 Integra (D16A1). Note: The 1986–1987 version utilizes a different architecture for the vacuum advance D16A1.
• 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 1990–1991 Integra.
• PR5: JDM Integra.
• PP5: UKDM Rover Cabrio.
• PS9: USDM Civic EX 4dr (D16A6 Automatic).
• PK2: JDM Prelude (B20A, electronic advance).
• PH3: JDM 1986–1989 Accord (B20A).

Tuning and Development#

Important

Chipping 1988–1989 ECUs is significantly more complex than 1990–1991 models, as the earlier units lack replaceable external ROM sockets.

To facilitate custom development, refer to the OBD0 Inter-Chip Communication0 documentation to understand the data exchange between the MCU and peripheral ICs.

For PCB design and reverse engineering, an Eagle (v4.09) library is available containing the following device footprints:

• Oki 8xC154 MCU
• M5128 RAM
• µPD7004 ADC
• Oki 6260A Engine Control Counter IC