Here we come to my favorite part of the Range Rover EAS. The EAS Electronic Control Unit (ECU) is a very elegant and highly efficient microprocessor driven sub-system. The EAS ECU performs all of the logic processing and logic signaling for the EAS operation. The ECU monitors all four EAS sensors and periodically makes adjustments to the suspension height. The ECU also monitors any user input from the EAS buttons and changes the suspension height accordingly. The EAS pump and each of the solenoid air valves are also driven by the EAS logic signaling. All of this comes together to create the sometimes interesting behaviors of the EAS.
At the heart of the ECU is a Motorola 68HC05 series microcontroller. This microprocessor is surrounded by a huge array of voltage shifting, inverting and conditioning circuitry. There is an extremely abundant collection of information about the Motorola 68HC05 processor avaliable on the web. It was these documents that allowed me to create a best guess about the EAS serial physical layer communications protocol.
The unit is extremely durable and rugged. I have heard of people manually hooking up the voltages accidentally in reverse with no adverse affects. Although I would not recomend this.
The Massive multiplug that connects the EAS ECU to all the various suspension components is labeled as Connector C117. The function of each connector on the C117 multiplug is listed below:
Read and clear this fault code yourself with the EAS Unlock V4 for the P38 Range Rover.