For Ford owners and automotive enthusiasts keen on comprehensive vehicle diagnostics, understanding and accessing your car’s communication networks is crucial. While standard OBD2 scanners provide valuable engine data, they often scratch the surface. To truly delve into your Ford’s systems, especially models like the 2008 Ford Taurus X, accessing the Medium Speed Controller Area Network (MS-CAN) alongside the High Speed CAN (HS-CAN) is essential. This guide will walk you through modifying a budget-friendly ELM327 adapter to unlock MS-CAN access, significantly expanding your diagnostic capabilities and allowing you to retrieve a wider range of Parameter IDs (PIDs) and run in-depth tests.
Understanding CAN Bus in Your Ford
Modern vehicles, particularly those from 2004 onwards, utilize CAN bus systems – sophisticated digital networks that allow various modules within your car to communicate. Think of it as a local network for your vehicle, connecting different electronic control units (ECUs) much like computers in an office. Before CAN bus, older OBD-II systems relied on protocols like SAE J1850 PWM. While still functional with tools like FORScan, these are less comprehensive than CAN-based diagnostics.
You might be wondering, “What are HS-CAN and MS-CAN?” In essence, vehicles manufactured before 2013 typically feature two distinct CAN buses:
- HS-CAN (High-Speed CAN): This network handles critical, time-sensitive data, primarily related to powertrain functions (PCM), safety systems like ABS and airbag control (RCM), and other essential operations.
- MS-CAN (Medium-Speed CAN): MS-CAN manages less time-critical but equally important systems within the vehicle’s interior, such as climate control (HVAC), audio systems (ACM), body control functions (SJB/BCM), and more.
In newer Ford models (2013+), the complexity increases, with up to four CAN buses (three HS-CAN and one MS-CAN) managing a vast amount of data from virtually every electronic component, from headlight switches to seat adjustments.
Both HS-CAN and MS-CAN networks are interconnected through the instrument panel cluster (IPC), enabling data sharing when necessary. However, to directly access and diagnose modules on the MS-CAN bus using an OBD2 adapter, modification of a standard ELM327 device is often required.
Why Modify Your ELM327 for MS-CAN?
Standard, unmodified ELM327 clones typically only communicate over the HS-CAN bus. This limitation restricts your ability to diagnose issues beyond the engine and powertrain. By modifying your ELM327, you gain access to a broader spectrum of modules and diagnostic data, including those on the MS-CAN bus, which is particularly beneficial for diagnosing systems like:
- Body Control Module (BCM/SJB)
- Heating, Ventilation, and Air Conditioning (HVAC)
- Audio System (ACM)
- Seat Modules (DSM, DCSM)
- Lighting Control (ILCM)
- And many more!
For owners of vehicles like the 2008 Ford Taurus X, this expanded access means you can troubleshoot a wider array of potential issues yourself, potentially saving on diagnostic costs at a mechanic and gaining a deeper understanding of your vehicle’s systems and OBD2 PIDs across different modules.
Modules on HS-CAN and MS-CAN
Here’s a more detailed breakdown of typical modules found on each CAN bus in Ford vehicles:
HS-CAN Modules:
- PCM (Powertrain Control Module)
- ABS (Anti-lock Brake System, including AdvanceTrac and Traction Control)
- RCM (Restraint Control Module, airbags, seatbelts)
- AWD (All-Wheel Drive module, if equipped)
- OCSM (Occupant Classification System Module, passenger seat sensors)
- PAM (Parking Aid Module)
- IPC (Instrument Panel Cluster)
- PSCM (Power Steering Control Module, hydraulic power steering)
- SECM (Steering Effort Control Module, electric power steering)
- CCM (Cruise Control Module)
- APIM (Accessory Protocol Interface Module, 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, BLIS)
- IPC-MS (Instrument Panel Cluster – MS-CAN communication)
- GPSM (Global Positioning System Module)
- APIM (Accessory Protocol Interface Module, SYNC – also on HS-CAN)
Note: Module presence can vary based on vehicle model and options.
For a visual representation of module connections, refer to diagrams like this example from a 2011 Ford vehicle:
Diagram of 2011 Ford CAN Bus Modules
Modifying Your ELM327 Adapter: Step-by-Step Guide
Modifying your ELM327 clone to access MS-CAN is a straightforward process requiring basic soldering skills and a few components. You’ll need a Double Pole Double Throw (DPDT) switch. This switch will allow you to toggle between connecting the ELM327 chip to either the HS-CAN or MS-CAN pins in your vehicle’s OBD2 port.
A Double Pole Double Throw (DPDT) switch is essential for selecting between HS-CAN and MS-CAN communication.
These instructions are adapted from FORScan’s helpful guide: http://forscan.org/howto.html
Tools and Components:
- ELM327 clone adapter
- DPDT switch
- Soldering iron and solder
- Wire strippers/cutters
- Heat shrink tubing (optional, but recommended)
- Small Phillips head screwdriver
Steps:
- Open the ELM327 Enclosure: Most ELM327 clones are held together with screws hidden under a sticker. Carefully remove the sticker and unscrew the enclosure to access the circuit board.
- Disconnect OBD-II Connector Wires: Unplug the OBD-II connector from the circuit board if possible. Identify and carefully desolder the wires connected to pins 6 (CAN High) and 14 (CAN Low) on the OBD-II connector. Crucially, mark these wires so you know which is which for correct reconnection.
- Solder New Wires to HS-CAN Pins: Solder two new wires to pins 6 and 14 on the OBD-II connector. These will be your HS-CAN wires.
- Solder New Wires to MS-CAN Pins: Solder two more new wires to pins 3 and 11 on the OBD-II connector. These will be your MS-CAN wires.
- Connect Original Wires to Switch (Middle Poles): Solder the wires you originally desoldered from pins 6 and 14 (the ELM327’s original CAN wires) to the two middle poles of the DPDT switch.
- Connect HS-CAN Wires to Switch (One Side): Solder the new wires connected to OBD-II pins 6 and 14 to one side of the DPDT switch. Ensure correct polarity – the wire originally from pin 6 should connect to the corresponding pole on the switch side.
- Connect MS-CAN Wires to Switch (Other Side): Solder the new wires connected to OBD-II pins 3 and 11 to the other side of the DPDT switch. Again, maintain polarity – the wire connected to pin 3 should align with the pin 6 polarity from the original wiring.
Important Polarity Note: Double-check and ensure you do not mix up HS-CAN and MS-CAN wires and maintain correct polarity throughout the wiring process. Incorrect wiring can potentially damage your vehicle’s electronics or the ELM327 adapter. Using different colored wires for HS-CAN and MS-CAN can help prevent confusion (e.g., red for HS-CAN, black for MS-CAN).
Wiring Diagrams for Reference:
These diagrams illustrate the wiring concept, showing the OBD2 connector from the dash connector view (remember to reverse this perspective when working on the scan tool connector):
Wiring diagram illustrating the DPDT switch integration for HS-CAN and MS-CAN selection.
OBD2 port pinout diagram highlighting pins for HS-CAN (6 & 14) and MS-CAN (3 & 11).
Visual Guide – Modification Process:
Below are images showcasing a typical ELM327 modification process:
My ELM327 motherboard:
ELM327 Motherboard Image
Image of an ELM327 clone’s circuit board, ready for modification.
Wires soldered onto the OBD-II connector:
OBD-II Connector Wiring Image
Wires soldered to the OBD-II connector pins for HS-CAN and MS-CAN connections.
Switch installed (heat shrink recommended):
DPDT Switch Installation Image
DPDT switch installed within the ELM327 enclosure to facilitate CAN bus selection.
Completed modification, ready for reassembly:
Modified ELM327 Internal View
Internal view of the modified ELM327 with the switch and wiring neatly arranged before closing the case.
Finished modified ELM327 adapter:
Finished Modified ELM327
The completed modified ELM327 adapter, now capable of accessing both HS-CAN and MS-CAN networks.
Accessing MS-CAN with FORScan
Once your ELM327 is modified, using software like FORScan to access MS-CAN is straightforward.
Upon launching FORScan with your modified adapter connected to your 2008 Ford Taurus X (or other compatible Ford vehicle), the software should detect the modification and ask if you have an MS/HS-CAN switch. Select “YES.”
FORScan prompting the user to confirm the presence of an HS/MS-CAN switch for modified adapters.
You might need to delete your vehicle profile in FORScan, close and reopen the program, and then reconnect for this prompt to appear consistently.
With the switch set to MS-CAN and FORScan configured correctly, you can now run diagnostic tests and access OBD2 PIDs across a significantly expanded range of modules compared to a standard OBD2 scan limited to HS-CAN. This includes running self-tests and retrieving data from modules on both HS-CAN and MS-CAN networks, as illustrated in this FORScan module list:
Example of a FORScan module list showing access to both HS-CAN and MS-CAN modules after ELM327 modification.
By modifying your ELM327 adapter, you’ve unlocked a powerful and cost-effective way to perform in-depth diagnostics on your Ford vehicle, gaining access to valuable data and control functions previously only available with professional-grade scan tools. This enhanced capability is particularly beneficial for owners of vehicles like the 2008 Ford Taurus X seeking to understand and maintain their car’s complex electronic systems.
Download FORScan to begin exploring the full diagnostic potential of your modified ELM327 adapter.
