Can Bus Info

Note: Only 2004+ vehicles will have CAN bus (basically if you have digital display in your instrument cluster). OBD-II cars before that used the SAE J1850 PWM protocol, which will still work with FORscan. FORscan only supports Ford and Mazda vehicles.

Now some of you may be asking: "What in the heck is this guy talking about... MS and HS-CAN???" CAN stands for Controller Area Network, and it's a digital network that connects different modules in your car much like computers would be connected to a network (LAN) in your home or workplace. Accessing the data and self-tests on this network will be useful if you want to troubleshoot problems with something other than the engine (like with the ABS or air bags for example). In the past you used to have to buy very expensive scan tools and software to view this data, but now you can can have this information at your fingertips for as little as $10!

There are two separate CAN buses on most vehicles before 2013, called HS-CAN (High Speed) and MS-CAN (Medium Speed). HS-CAN is used for 'priority' data, like engine parameters (PCM) and critical communication between safety modules like the ABS and RCM. MS-CAN is used more for things inside the car like radio, climate, and lighting control.

In new cars (2013+), nearly every function and control goes over a CAN bus. They have four CAN buses (3x HS and 1x MS) because there is much more data flying around. Things on CAN would be your headlamp switch, drivers door switches, hazard lights, turn signal stalk, dimmer switches, seat adjustments, mirror adjustments, any button on your dash, you name it! I need to scan a 2013+ Ford to actually find out what modules there are!

The HS and MS-CAN buses are bridged together in the instrument panel cluster (IPC) so data can be shared between networks if required.

HS-CAN modules:
-PCM (Powertrain Control Module)
-ABS (Anti-lock Brake System, includes AdvanceTrac and Traction Control)
-RCM (Restraint Control Module, AKA airbags and seatbelts)
-AWD (All Wheel Drive module, if equipped)
-OCSM (Occupent Classification System Module, AKA Passenger Seat Sensors)
-PAM (Parking Aid Module)
-IPC (Instrument Panel Cluster)
-PSCM (Power Steering Control Module, Hydraulic PS only)
-SECM (Steering Effort Control Module, Electric PS only)
-CCM (Cruise Control Module)
-APIM (Accessory Protocol Interface Module AKA SYNC)

MS-CAN modules:
-SJB/BCM (Smart Junction Box/Body Control Module)
-HVAC (Heating, Ventilation & Air Conditioning module)
-ACM (Audio Control Module)
-DSP (Audio Digital Signal Processing Module)
-DSM (Driver Seat Module)
-DDM (Driver Door Module)
-RFA (Remote Function Actuator Module)
-DCSM (Dual Climate Controlled Seat Module)
-SDARS (Satellite Digital Audio Radio Service)
-FCIM (Front Controls Interface Module)
-FDIM (Front Display Interface Module)
-ILCM (Interior Lighting Control Module)
-HCM-2 (High Beam Control Module)
-SOD-R/L (Side Obstacle Detection Control Module AKA BLIS, a module for each side of the vehicle)
-IPC-MS (Instrument Panel Cluster)
-GPSM (Global Positioning System Module)
-APIM (Accessory Protocol Interface Module AKA SYNC)

There may be other modules on other cars or less modules on some cars. Here's a diagram from a 2011 that show all the modules connected to the CAN: http://revbase.com/BBBMotor/Wd/DownloadPdf?id=875110