I have 2005 2.0 ford focus and would like to know what diagnostic reader is compatible?

A modified elm327 and forscan is the best. There's loads of info on the forum about it.

What modifications have to be done on the elm327?

The modification to the ELM327 cable is a physical or electronic switch to allow Forscan to access both the high-speed and medium-speed CAN buses.

Hello Craig, welcome to the Ford Owners Club - you don't actually modify the lead yourself, its just what its called. Loads for sale on eBay, don't order from China or you will wait till Christmas for it.

You need something like this: https://www.ebay.co.uk/itm/ELM327-USB-modified-fits-Ford-ELMconfig-latest-chip-HS-CAN-MS-CAN-Forscan-OBD2/203253858823?hash=item2f52dfc207:g:QioAAOSwd5VgCAou

your first post said diagnostic reader, 

to meet that question a £10 bt obd dongle and a free or £5 quid app will meet what you asked.

 

the replies and yourself then took a huge leap in to programming - if you want to play the fake Chinese ones are not the way to go

forscan spent last few years trying to make one that was fit for purpose... in the last 2 months they added this link on their website re. where to get one https://www.bmdiag.co.uk/obdlink-ex-forscan-diagnostic-for-ford-usb-cable

 

 

If you want something cheaper the original Tunnelrat modified ELM with manual switch is available here. Tunnelrat have a good reputation and individually test all their cables before despatch. I have one and it works very well.

and then you read the Forscan pages and it specifically says it can't operate correctly with a cheap cable and thus may not show various modules fitted to the car as it needs to communicate across both can-bus speeds at the same time... and a toggle switch version doesn't have this capability

7 minutes ago, Botus said:

and then you read the forscan pages and it specifically says it can't operate correctly and may not show various modules as it needs to communicate across both can-bus speeds at the same time... and a toggle switch version can't do this

Can you send us a link? I haven't come across anything that needs both HS and MS at the same time, Forscan brings up a promt asking you to flick the switch whenever I've done stuff.

Hi Luke, as far as I have seen Forscan could not operate both HS and MS at the exact same time. As you correctly point out Forscan actually has a promt asking you to select either the MS or HS as required.

On 4/16/2021 at 4:35 PM, Luke4efc said:

Can you send us a link? I haven't come across anything that needs both HS and MS at the same time, Forscan brings up a promt asking you to flick the switch whenever I've done stuff.

 

https://forscan.org/forum/viewtopic.php?f=4&t=6142    written March 2018 section 3 reliability

 

Two things are important for reliability:

- quality of the adapter. Non original adapters in general case have lower quality than original ones. We will create a dedicated article about so-called "clone problem".

- type of interface. The fact is that wireless interfaces used in ELM327 family of adapters are much less reliable than USB interface. And this problem is actual not only for "clones", but also for "original" adapters (OBDLink MX WiFi and Viaken VScan Bluetooth are most obvious examples).
 

Also, important note about adapters with mechanical HS/MS switch: in addition to the fact it is not very convenient to switch it manually, it may be not possible to perform some operations with this type of adapter. If some operation requires a simultaneous access to both HS and MS (so FORScan needs to access some module(s) on HS CAN bus and, at the same time, other modules on MS-CAN bus), it cannot be normally executed using adapters with mechanical switch. Example: reading parameters (PIDs) in virtual module All, Module initialization subfunction in service functions "Remote keyless entry and Start".

 

elsewhere it specifically states if you have EVER connected to Forscan with a toggle switch for this car it will  NEVER show the missing modules, even when you revert to a good cable  I had this problem, it then says clear the Forscan cache to get over it.  But it wouldn't !!  I had to wipe the tool from the PC, clear the registry and start again. When I asked Forscan about it they just said it won't work - they didn't even offer a how to fix !!!

 

 

I’d flushed the cache, but not seeing more modules than I did with the manual switching cable?

OBDLink EX is faster (up to 4x times on some operations), more stable and convenient (no need to switch HS/MS CAN switch manually). But if your former adapter had HS/MS CAN switch and you used it properly, it will not find new modules for you.