For automotive enthusiasts and DIY mechanics, accessing comprehensive vehicle diagnostics is crucial. While standard OBD2 scanners are invaluable tools, they often have limitations, particularly when it comes to accessing Medium Speed CAN (MS-CAN) networks in modern vehicles. If you’re looking to deepen your diagnostic capabilities without investing in expensive professional tools, modifying an inexpensive ELM327 scanner to read both MS-CAN and High Speed CAN (HS-CAN) data might be the best upgrade for your OBD2 setup. This guide will walk you through the process of modifying your ELM327 clone, unlocking a wider range of diagnostic information from your Ford or other compatible vehicle.
Understanding CAN Bus Networks: HS-CAN vs. MS-CAN
Before diving into the modification process, it’s important to understand the Controller Area Network (CAN) bus system in modern vehicles. Think of the CAN bus as your car’s internal network, similar to a computer network in your home or office. This network allows different electronic control modules (ECMs) within your vehicle to communicate with each other. For vehicles manufactured from 2004 onwards, CAN bus systems are standard, often replacing older protocols like SAE J1850 PWM.
Within the CAN bus architecture, there are typically two main types of networks:
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HS-CAN (High-Speed CAN): This network is used for critical, time-sensitive data communication. It handles priority information such as engine control parameters from the Powertrain Control Module (PCM), Anti-lock Brake System (ABS) data, Restraint Control Module (RCM) information (airbags and seatbelts), and more. HS-CAN ensures rapid and reliable communication for essential vehicle functions.
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MS-CAN (Medium-Speed CAN): MS-CAN operates at a lower speed and is generally used for less critical, body and comfort-related systems. This includes modules like the Smart Junction Box (SJB), Heating, Ventilation & Air Conditioning (HVAC), audio systems, door modules, and interior lighting controls. Accessing MS-CAN data expands your diagnostic reach beyond engine and safety systems to include a wider array of vehicle functionalities.
In newer vehicles (2013+), the CAN bus architecture has become even more complex, with some vehicles employing multiple HS-CAN networks in addition to MS-CAN to manage the increasing volume of data. These networks are often bridged through the Instrument Panel Cluster (IPC) or a dedicated gateway module to allow data sharing between different systems.
Knowing the distinction between HS-CAN and MS-CAN is crucial for understanding why modifying your ELM327 scanner can be a significant upgrade for comprehensive vehicle diagnostics.
Why Upgrade to MS-HS CAN OBD2? Expanding Your Diagnostic Horizon
Standard ELM327 scanners, in their original configuration, are designed to read only HS-CAN data. This means you can access engine-related diagnostics and some safety system information. However, to truly troubleshoot issues beyond the powertrain, such as problems with your car’s electronics, climate control, or body control systems, accessing the MS-CAN network is essential.
By modifying your ELM327 to read both MS-CAN and HS-CAN, you gain the ability to:
- Perform deeper diagnostics: Access a broader range of modules and systems within your vehicle, including body control, comfort, and convenience features.
- Run comprehensive self-tests: Utilize software like FORScan to perform self-tests on modules connected to both HS-CAN and MS-CAN, identifying potential issues that a standard OBD2 scan might miss.
- Troubleshoot a wider range of problems: Diagnose issues related to systems like ABS, airbags, climate control, lighting, door modules, and more, all with a single, modified scanner.
- Save money on professional diagnostics: Empower yourself to perform advanced diagnostics at home, potentially avoiding costly trips to a mechanic for issues beyond basic engine codes.
For Ford vehicle owners, software like FORScan is particularly powerful when paired with a modified MS-HS CAN OBD2 scanner. FORScan is designed to tap into the full diagnostic capabilities of Ford vehicles, and MS-CAN access is critical to leveraging its complete feature set.
DIY: Modifying Your ELM327 for MS-HS CAN
Modifying your ELM327 scanner to access MS-CAN involves a relatively simple hardware modification using a DPDT (Double Pole, Double Throw) switch. This switch allows you to toggle between connecting the ELM327 chip to either the HS-CAN or MS-CAN pins on the OBD2 connector of your vehicle.
What You’ll Need:
- ELM327 OBD2 clone (easily purchased online)
- DPDT Switch (Dual Position, Dual Pole)
- Soldering iron and solder
- Wire strippers/cutters
- Small gauge wires (different colors recommended for HS-CAN and MS-CAN)
- Heat shrink tubing (optional, but recommended for insulation)
- Screwdriver (to open the ELM327 enclosure)
Modification Steps:
Step 1: Open the ELM327 Enclosure.
Carefully open your ELM327 clone. Typically, there are four screws hidden under the sticker. Remove these screws to access the circuit board.
Step 2: Disconnect HS-CAN Wires.
Identify and unsolder the wires connected to pins 6 and 14 on the OBD-II connector inside the ELM327. These are the original HS-CAN wires. Important: Mark these wires so you know which one was connected to pin 6 and which was connected to pin 14. Polarity is important.
Step 3: Solder New HS-CAN Wires.
Solder two new wires to pins 6 and 14 on the OBD-II connector. These new wires will eventually connect to the switch.
Step 4: Solder MS-CAN Wires.
Solder two more new wires to pins 3 and 11 on the OBD-II connector. These are the MS-CAN pins.
Step 5: Connect Original HS-CAN Wires to the Switch.
Solder the wires you originally removed from pins 6 and 14 (from Step 2) to the two middle poles of the DPDT switch.
Step 6: Connect New HS-CAN Wires to the Switch.
Solder the new wires you attached to pins 6 and 14 (from Step 3) to one side of the DPDT switch. Ensure you maintain polarity – the wire that was originally on pin 6 should be paired with the new wire from pin 6.
Step 7: Connect MS-CAN Wires to the Switch.
Solder the wires you attached to pins 3 and 11 (from Step 4) to the other side of the DPDT switch. Again, maintain polarity – the wire that you intend to correspond to pin 6 polarity should be consistent throughout.
Safety First: Double-check all your connections and ensure you have not mixed up the HS-CAN and MS-CAN wires. Incorrect wiring can potentially damage your vehicle’s electronics. Using different colored wires for HS-CAN and MS-CAN can help prevent mistakes. Red for HS-CAN and Black for MS-CAN is a common practice.
A helpful visual guide is the wiring diagram:
For clarity, these diagrams illustrate the wiring in a simplified manner. Remember that the OBD2 connector pinout is mirrored on the scan tool side.
Here are some images illustrating the modification process:
An ELM327 motherboard, showing the components before modification.
Wires soldered onto the OBD-II connector pins for both HS-CAN and MS-CAN access.
A DPDT switch installed within the ELM327 enclosure to toggle between HS-CAN and MS-CAN modes.
The modified ELM327 partially reassembled, showing the hole cut for switch access.
The completed MS-HS CAN modified ELM327 OBD2 scanner, ready for use.
Unleashing MS-HS CAN: Using FORScan
Once you have modified your ELM327 scanner, you can utilize software like FORScan to access the expanded diagnostic capabilities. When you launch FORScan with your modified scanner connected, the program should detect the MS-HS CAN switch.
FORScan may prompt you with a question like this:
Select “Yes” to indicate that you have a modified scanner. You might need to delete your car’s profile in FORScan and reconnect for the software to recognize the switch initially.
With the MS-HS CAN capability enabled in FORScan, you can now access a wider range of modules and perform tests across both networks. This allows you to read diagnostic trouble codes (DTCs), view live data, and run service procedures on modules that were previously inaccessible with a standard ELM327 scanner.
Here’s an example of the expanded module access you might see in FORScan after the modification:
A screenshot showing the expanded list of modules accessible in FORScan after MS-HS CAN modification.
Conclusion: Enhanced Diagnostics at Your Fingertips
Modifying your ELM327 OBD2 scanner for MS-HS CAN access is a cost-effective and empowering upgrade for any DIY automotive enthusiast. By adding this simple switch, you unlock a significantly broader range of diagnostic capabilities, allowing you to delve deeper into your vehicle’s systems and troubleshoot issues beyond the engine and basic OBD2 functions. Paired with powerful software like FORScan, your modified scanner becomes a valuable tool for comprehensive vehicle maintenance and repair, truly making it one of the best upgrades for your OBD2 setup.
