How to access MS CAN bus using FORScanV2 and modified ELM327

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How to access MS CAN bus using FORScanV2 and modified ELM327

Postby FORScan » Sun Jun 15, 2014 1:43 pm

Many Ford and Mazda models (approximately since 2003-2004) are equipped with MS CAN bus, in addition to the regular HS CAN bus. In contrast to HS CAN bus, MS CAN bus is not supported by the stock ELM327, because MS CAN is a manufacturer-specific solution and located on non-OBD2 pins. However, ELM327 is very flexible tool, and small modification allows to implement the MS CAN support.

Note before you read further: since version 2.1.0 FORScan supports the STN11XX chip with a built-in MS-CAN bus support (example of adapter implementation: OBDLink MX, ELS27). So it may be better choice for people who wouldn't like to modify anything by their own hands.

Note for Mondeo Mk3 owners: only models after restyling in July 2003 have MS-CAN modules. And this bus only keeps few modules like ACM and EATC. You do NOT need the MS-CAN modification to access engine, ICU and all other modules except ACM and EATC.

This article contains of 2 parts: How to modify ELM327 in order to add the HS/MS CAN switch, and some notes about MS CAN support in FORScan v2.

Note: If FORScan doesn't ask you about HS/MS CAN switch (see chapter 2 below), it means it doesn't suspect MS CAN modules on the board and will not check for them, even if you modify the ELM.

1. How to modify ELM327 in order to add the HS/MS CAN switch

ELM327 supports HS CAN from the stock, because Ford HS CAN completely matches to the OBD2 standards. It occupies pins 6 and 14. MS CAN bus occupies pins 3 and 11. The picture below illustrates the thing (ATTENION: the OBD2 jack on the picture means vehicle one, "female". The adapter's one is "male", so it is "mirrored". Pins are often mixed up because of this. Always note pins' numbering of the adapter's jack!):

Image

The simplest way to implement the MS CAN support is to add a switch that will shift between MS/HS CAN. The scheme below explains the modification (ATTENION: the OBD2 jack on the picture means vehicle one, "female". The adapter's one is "male", so it is "mirrored". Pins are often mixed up because of this. Always note pins' numbering of the adapter's jack!):

Image

Roadmap:

  • Purchase a 6 pin mini-switch of ON-ON type (for example, MTS-202-A2) in any shop that sells electronic components, also prepare a wire

    Image
  • Disassemble ELM327 (for majority of china clones - carefully remove the label that hides 4 screws, unscrew them)
  • Find a place for the mini-switch (most complex part of the whole operation for some devices that are extremely compact)
  • Unsolder wires from pins 6 and 14 of the OBD2 jack and solder them to the 2 middle pins of the mini-switch
  • Solder 2 new wires from 2 outer mini-switch pins to pins 6 and 14 of the OBD2 jack
  • Solder 2 other new wires from 2 other outer mini-switch pins to pins 3 and 11 of the OBD2 jack
  • Check the work (it is very important to do not mix CAN-L and CAN-H wires up!) and assembly the ELM327, mark the MS and HS can position on the device box to avoid confusion

Example of the modification:

Image

2. FORScan v2 MSCAN support

FORScan v2 has support of MS CAN bus and optimized for using the HS/MS CAN switch. There is no necessity to adjust any ELM327 parameters for MS CAN, FORScan makes all the necessary changes in an automated mode. When FORScan establishes a vehicle connection, it analyses the vehicle configuration. If MS CAN modules are expected, FORScan will ask user about HS/MS CAN switch:

Image

If no question is asked, it means FORScan doesn't expect a presence of MS CAN and is not going to look for it. If user confirms the MS/HS switch presence, FORScan will ask user to shift the bus, for example:

Image

FORScan v2 is optimized for using the HS/MS CAN switch (minimize number of necessary shifts). For example, reading DTCs in all of 5 HS CAN modules and 2 MS CAN modules will always require only 1 shift.
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