The PJ0 ECU, utilized in 1986–1989 Honda Accord and Prelude models equipped with the A20A engine, features various hardware revisions based on regional emissions requirements. While all variants utilize a vacuum-advance distributor, specific features such as O2 sensor feedback and EGR control vary by market.

Hardware Overview#

Most PJ0 ECUs were manufactured by Matsushita. Hardware architecture varies significantly between standard and California emissions-compliant units.

• Standard Units: Many 1986–1987 models utilize an external 128k ROM.
• California Emissions Units: These variants are based on the OKI 80C154 microcontroller and consistently utilize a 128k external ROM.

ECU Revisions#

The following images illustrate the physical differences between regional and emissions-specific PJ0 hardware.

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Note

Regional variants may lack specific emissions control hardware, such as O2 sensor inputs or EGR solenoid drivers. Verify your specific board revision before attempting to interface with emissions-related sensors.