This guide outlines the hardware modifications required to add a knock sensor circuit to a Honda P75 ECU board, effectively upgrading it to support P72 knock sensor functionality.

Installation Procedure#

1. Prepare ECU Board: Acquire a knock sensor board (e.g., from a P72 ECU).
2. Connector Strip: Install the connector strip. If using a JDM P72 board, you may need to move the connector strip from the connector port B to connector port A.
3. Resistor Modifications:
   • Remove R12.
   • Install R15 and R11 (100 Ohm resistors; you can reuse the removed R12 if appropriate).
4. Final Installation: Solder the knock board onto the P75/P72 conversion location (FC1).

Verification and Setup#

Once the hardware installation is complete, the ECU board should be functionally equivalent to a P72.

• Software Configuration: You must enable the knock sensor in your ECU management software/ROM configuration.
• Verification: Ensure all connections are secure and verify the knock sensor wiring on the engine harness side is correct.

Always verify your board layout and component markings before soldering. Knock sensor functionality is critical for engine protection in turbocharged or high-compression applications.