This document serves as a technical reference for diagnosing continuity issues after installing an external ROM socket and 74HC373 latch on an OBD1 Honda ECU. It outlines verified connections between the latch, ROM socket, 66K MCU, and support components.

Caution: Always disconnect the ECU from the vehicle before performing continuity testing.

Testing Procedure#

1. Inspect: Visually verify the 74HC373 latch and ROM socket for solder bridges.
2. Adjacent Pin Test: Use a continuity tester to ensure no adjacent pins on the packages have continuity.
3. Point-to-Point Test: Test for continuity between each package pin and its expected connection point using the wirelist below.

Wiring Reference#

(The wirelist is extensive; refer to the raw data files for full pin-to-pin mapping)

Technical Notes#

• DIP Pins: Numbering begins at pin 1 beside the notch or dot, running down the left side, then up the right side.
• RM3: Single-inline-package resistor pack; pin 1 is indicated on the silkscreen.
• JDM P30-901: Square surface-mount MCU pin 1 is in the center of one side.
• Active Low Signals: Signal names beginning with / are active low.