This is the Rear Electronics Module (REM) for models from 1998 to 2004. This module has the relays and fuses for the cargo compartment and also for the rear backlights.

^{Figure 1 - Rear Electronic Module (REM) with all wires and relays connected to the left. factory original hardware electronics to the right}

To view which functions this module operates and which fuses it connects choose an option below:

• relays Function
• fuses
• REM Connector Pinout

Status: ^{PCB Design >> PCB fabrication >> Component assembly >>} Testing

revision 06-2024
  The main REM microcontroller is the EspressIF Systems ESP32 S3 microcontroller a dual core Xtensa LX7 Core Processor running at 240MHz with 512Kb RAM and of 8MB PSRAM. This is the main MCU that is responsible for doing real-time engine management of a vehicle. This hardware revision is a totally new PCB design and a direct replacement of the factory REM found on P2 Volvos. The prototype boards are being fabricated for later testing.

^{Figure 3 - To the left, 3D rendering in KiCad of the current PCB revision; To the right, the current PCB revision being tested}

Interactive view of the PCB Layout   Interactive view of the circuit schematic
^{Click to view the latest revision}

  In regards to safety against theft the electronics will include a cryptographic IC that will be used to match the car owner's VIN number and with all other open hardware electronic components installed on a vehicle. In practical terms, this means, that in the event of theft, to make a specific open hardware work on another vehicle, will require the replacement of the main microcontroller processing unit without the need of specialized tools and equipment. More information about safety and sensor data validation on this sci. research paper titled "Validation of Experimental Data Origins: A Swarm of DAQ devices able to Deliver Unique Experimental Data using Blockchain‐like Fingerprint ID to a Data Repository".

  To run the electronics for CAN communications I'll be using EspressIF Systems ESP32 C3 microcontroller a single core Xtensa LX7 Core Processor running at 160MHz with 400Kb RAM and of 4MB PSRAM. This microcontroller is intended for communication with other hardware electronics in a vehicle and relays validated data to the main microcontroller. It has wireless radio capabilities that are disabled on the hardware electronics itself for safety concerns. Instead, the hardware includes a USB-C port for direct connectivity with the ECU.

Another important feature of this hardware electronics is the personal "CAR KEY". This is a customizable and programmable nano sim card that has stored a custom token access key up to 256 bytes. This access key is also present on any other module of the car and is constantly verified and checked for changes. Any unauthorized change disables running of the car. (learn more here).

The KiCad footprints for this open hardware electronics can be found here. To view the revision history of this OPEN REM click here.

For more information about wiring and connector pinout for this module click here.

• REM management powered by the ESP32 S3 microcontroller with a clock speed of 240MHz

  • 512kb of RAM
  • 8MB of SRAM
  • 16MB of flash storage

• Power management

  • Voltage sense in all relays
  • active power monitoring

• Module Communications

  • CANBUS FD ( ISO 11898-1.) network communications are managed by a dedicated microcontroller, the ESP32 C3 with a clock speed of 160MHz
  • K-Line communications (ISO 9141-2 ; ISO 14230-2)

• Security & Data Validation

  • Data Fingerprint ID for communications (learn more here)
  • Hardware electronics protected by a 256-bit security sim card "Car Key" (learn more here)

• USB-C connection

  • for firmware updates/upgrades
  • installation of Custom firmware possible ( tunning)
  • for local troubleshooting of errors on the module and on the CANBUS network

• Status RGB LED

• this REM allows adding more modules, it has a selectable CAN termination

• Electronic components delimited and well-identified for easier identification and repair

^{Figure 3 - Factory Original Plastic Enclosure for the Rear Electronic Module (REM)}