Introduction

Select Monitor Adapter
Subaru Diagnostic Ports
How to build a PC adapter
Protocol
Software
Troubleshooting
Eavesdropping

Engine Control Unit (ECU)
Description
Reading Error Codes
Reverse Engineering
Modifying
ROM images

Transmission Control Unit (TCU)
Description
Reading Error Codes
Reverse Engineering
Power Mode
Modifying
ROM images

Other Control Units
Air Conditioning Unit
4WS Control Unit
Cruise Control Unit

OBD2 Information
Select Monitor Cartridge

Downloads
Links to other sites

Custom TCU Development



Cruise Control Unit

Despite many attempts, I have not been successful in communicating with the SVX Cruise Control Unit.

The developers of FreeSSM discovered an older SSM protocol used by the Subaru L-series. They suggested to me that perhaps the cruise control unit uses this older protocol. It requires clocked synchronous communications and is therefore not compatible with our current design of RS232 to TTL interface.

From looking at the select monitor rom dump, I think that this is correct. The select monitor program appears to configure the serial interface for clocked synchronous communication at 250 baud. The extra wire on pin 4 of the diagnostic connector is presumably to carry the clock signal from the SSM to the CCU.