I have an intermittent fault that is producing a engine malfunction error on my LCD, if i am stationary at the time it happens, that's all i get, if i am driving at the time i get acceleration decreased and once i pull over and stop. all i get is the engine malfunction error.

Once i have stopped, 50% of the time i can turn it off and restart as normal, sometimes it just will not allow me start again. (Acts as if the immobilisers hasn't been disarmed and doesn't even try to crank and turn over) If i then clear the codes it will start as normal?

I have very limited fault finding equipment but i get  error 16 from the immobilizer flashes, and from the report produced by the AA man, i get the following.

U0140 - CAN communication with central electronics. Error Message : Fault in CAN communication.

U0155 - CAN communication with instrument cluster. Error Message : Fault in CAN communication.

P1935 - Brake switch signal. Error Message : Value implausible.

P1936 - Clutch switch P/N signal. Error Message : Value implausible.

P1622 - Unknown fault. Error Message : .Patrol found the following fault code/s:System : Engine control 1 - 54N / Diesel CR/EDC SID 202 Status

I took it to a garage but he couldn't be sure and it wouldn't go wrong for him. so i took it back and when it went wrong removed the instrument cluster and resoldered the main connector back onto the cluster as i was led to believe this was likely the problem. it was then fine again for a week but has gone again. does anyone have any ideas where to look next?

Aaron

8 hours ago, AMWLocksmiths said:

when it went wrong removed the instrument cluster and resoldered the main connector back onto the cluster

That cluster (IC) fault is very common on the 2006 Focus. I can't see your car year, but the CMax is closely related to the FOcus, and the IC may have come from the same supplier.

During de-soldering & re-soldering, it is possible to damage the pcb tracks. When I did mine, I put little links from the pin to the adjacent pads, photo is in: http://www.fordownersclub.com/forums/applications/core/interface/file/attachment.php?id=40491

If you did not de-solder & re-solder with new flux & solder, you may have left a dry joint underneath your new solder.

To test this problem, measure the CAN bus resistance as below:

Stick a couple of suitable probes (un-bent paper clips can work quite well) in the diagnostic connector pins 6-14, put a DMM across the pair on voltage range, turn ignition on, note reading, turn ignition off, wait till voltage drops to zero (+/- 1 or 2 mV), switch to resistance range to check for 60 ohms. It should be stable at close to 60.

Tapping the fascia around the IC may make it change. If so, the IC is faulty.

I used Forscan, a very powerful system that only costs £15 if you have a windows laptop. I had to use it to clear some "permanent" dtcs after the repair. It would be well worth getting it.

Other possibilities are any other connectors in the HS CAN bus. In the Focus, there is one in front of the passenger door, behind the trim panel there. There is also one in the engine bay fusebox.

See if any of that helps.

---- Forscan info ---

Forscan is a powerful Ford specific system, Cost £15.00 for the interface. Needs a computer of some sort. (COM port, USB, Bluetooth or WiFi interfaces available). You will find a lot about ELM327 & Forscan on this site, which together provide a very comprehensive diagnosis & maintenance tool. James (jeebowhite) has done a nice guide: http://www.fordownersclub.com/forums/applications/core/interface/file/attachment.php?id=21196

Forscan works best on a Windows laptop, with a USB ELM. The Tunnelrat one (below) has been reported to work well by several people. Forscan is also available for iOS & Android for some tablets & phones.

For a USB ELM327 adapter, see
http://www.spanglefish.com/TunnelratElectronics/index.asp?pageid=516992

Wireless ELMs are also available (bluetooth & WiFi), but are often not as reliable as the wired ones. Also they are rare in the "modified" form which is needed to access the 2nd Ford bus system. This 2nd bus is the MS-CAN bus, and links all the car interior electronics like door modules, and the BCM (aka GEM). But a standard ELM will still work with all the Underbonnet Modules (PCM, ABS etc) and with the IC (Instrument Cluster).

For an bluetooth wireless ELM, which one user at least says works with Forscan, see the KW902: http://www.ebay.co.uk/itm/ELM327-KW902-Bluetooth-Scaner-OBD-Link-OBD2-Diagnose-Interface-Tester-white-UK-/281631334205

The Forscan programme is free (in Windows format) and you can get it from:
http://forscan.org/download.html