Good morning all, I have a 2009 ford Focus 1.8tdci that has just started throwing all sorts of faults up and going into limp mode with the engine malfunction light up. They will clear and the car may drive OK for the next day or so. I was hoping for advice of the first avenue of diagnosis. The codes that came up this morning were: 

P1204 - Cylinder No. 4 Injector Circuit Open/Shorted,

C1306 - Steering wheel angle sensor zero position not found,

U2023 - Vehicle Communication Network Fault,

U1900 - CAN communication bus fault,

C198F - Lost Communication with Switch Pack,

U0201 - Lost Communication With Door Control Module C and

U1900 - CAN communication bus fault.

I believe the first one causes the car to run poorly but I don't know why all the others are coming up as well

DTC_2024-11-22_07.36.56.txt

With all those 'U' codes this is almost certainly the very common instrument cluster cracked solder joint problem. There are many threads on the forum about it if you do a search.

I suspect there are 2 problems here.  Almost certainly a cluster fault.  But I've never seen an injector code caused by that so far, so potentially a faulty injector (or loom) as well.

I would get the cluster resoldered anyway as these are ticking time-bombs due to the use of lead-free solder. If you don't feel confident doing it yourself member  @rd457 offers a repair service.

Once that's done clear the DTCs and see if any come back. If the injector code reappears you'll then know that needs investigating further.

I concur with all of the above. Here's my service if you want to use it: https://www.ebay.co.uk/itm/314393033915

On 11/22/2024 at 4:39 PM, mjt said:

I would get the cluster resoldered anyway as these are ticking time-bombs due to the use of lead-free solder. If you don't feel confident doing it yourself member  @rd457 offers a repair service.

Once that's done clear the DTCs and see if any come back. If the injector code reappears you'll then know that needs investigating further.

Hi mjt, I re-soldered the solder joints for the plug in the instrument cluster and took it for a drive. I drove for about an hour on and off and thought I had cured the problem. Sadly it had an engine malfunction warning came up on the way home. As I was on a dual carriageway at the time I was more interested in clearing the faults and getting home than checking what they were but there were definitely some U codes. I am thinking of checking that I have good reliable earths on the car but besides the obvious chassis earth by the battery I am not sure where else to check. Any advice on this approach would be good. I will take it out again around the local roads tomorrow evening and see what codes come up and see if the injector one re-appears. Thank you for the advice so far.

47 minutes ago, NigeB70 said:

, I re-soldered the solder joints for the plug in the instrument cluster and took it for a drive.

Did you remove all of the old 'lead free' solder before using new lead/tin solder ? If not then you will still get problems with high resistance joints.

As above, if you simply reflowed the solder you may still have bad joints. You need to remove the old solder - I find solder wick the most effective for this - and resolder with 60/40 lead solder.

Thanks for the advice. You are correct in thinking that I only re-flowed and added solder. I will remove the old solder with the braid I have and try again.

I did as advised and desoldered first. I drove it for about 30 miles with no warnings so hopefully that fixed it. The car is now making a strange knocking noise so haven't driven any further but thanks for your assistance.