PJ0 ECU Reference (Accord/Prelude A20A, 1986–1989)
The PJ0 ECU for 1986–1989 Accord/Prelude A20A engines exists in multiple regional variants with differing O₂ sensor and EGR control configurations.
Overview
The PJ0 ECU for 1986â1989 Accord and Prelude A20A engines was produced across multiple regional markets with significant hardware variations. Certain variants omit Oâ sensor and EGR control functionality, though all models retain vacuum-advance distributor support.
Note
Most PJ0 ECUs were manufactured by Matsushita. Early models (1986â1987) may use an external 128 KB ROM. California emissions variants are based on the OKI 80C154 microcontroller and always employ external 128 KB ROM storage.
Manufacturing and ROM Configuration
| Variant | Manufacturer | ROM Type | Notes |
|---|---|---|---|
| Standard (non-CA) | Matsushita | Internal or 128 KB external | Typical configuration for most markets |
| California emissions | OKI 80C154 | 128 KB external (always) | Stricter emissions compliance required |
| Early models (86â87) | Matsushita | 128 KB external | Transition period equipment |
Known Variants
Canadian 1989 Accord (Matsushita)
- Part Number: PJ0-A03
- Manufacturer: Matsushita
- Notes: Standard domestic variant
1989 EDM A20A4 (No EGR, No Oâ Sensor)
- Part Number: PJ0-604-2
- Application: EX-i trim, 1989 model year
- Configuration: EGR and Oâ sensor functionality disabled
- Variant Type: EDM (Engine Data Module)
California Emissions Variant
- Part Number: PJ0-L022
- Microcontroller: OKI-based architecture
- ROM: 128 KB external (required)
- Certification: California Air Resources Board (CARB) compliant
1986â1987 Prelude SI (USDM)
- Part Number: PJ0-666
- Application: United States Domestic Market (USDM) Prelude SI
- Years: 1986â1987 model range
Important
Variant availability varies significantly by region and model year. Verify ECU hardware revision against engine block and VIN before modification or replacement.