The PM9 ECU is functionally equivalent to the PM5 ECU, with variations typically attributed to transmission configuration (4-speed vs. 5-speed). The PM9 is commonly found in the 1988–1991 Honda Civic HF.

Hardware Revisions#

The PM5 and PM9 platforms utilize two distinct hardware designs, similar to the PG7 architecture. Hardware identification is determined by the onboard processor:

• 1988–1989: Utilizes the 83C154 processor.
• 1990–1991: Utilizes the 66201 processor.

Note

The 1990–1991 processor quadrant layout shares significant design similarities with OBD1-era ECU architectures.

Component Overview#

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Technical Specifications#