Hi everyone, I have a Ford Focus MK2 2005 2.0 and I've had the U1900 engine code pop up and I've tired everything to get rid of it. Its been on for a while but I haven't been driving for a while either. i drove it for a couple mins up and down the road with the light on and it was fine. only a couple days later it doesn't start and I have the immobilizer light flashing giving the code 14. I read this is irrelevant when the U1900 code is present. which I believe as the car recognizes the key as it locks and unlocks. Id love any input on this. to save time, the tings I've already done are as follows.

- Re-soldering the instrument cluster, no change

- Cleaned up all the ground point to bare metal 

- Re-charged the battery over night

- Tested the PCM/ECU and a solid 12v power is present when the key is turned

- Ensured all wires were in good condition with no cracks

- Also that all the connectors were in tact

- All the fuses and relays are fine and work

- Both fuse boxes have power

- Tried using the OBD II reader to clear the code but 'erase failed' is displayed

- Tapped the top dash a few times above the cluster 

I did my own test and disconnected the throttle body then turned the cars electrics on. The code reader then displayed two more codes, related to the throttle body as expected. speed limited mode and engine systems failure were also displayed. After connecting the body back to the loom the codes disappeared and only U1900 was displayed as before. I'm pretty sure this tells me that the communication between the cluster and PCM is fine? On the other hand I've had both speed limited mode and engine system failure displayed before when just starting the car but it disappeared. is it possible the U1900 is related to the throttle body now? how would I test this or other components. everything has power and all connections and wires seem real fine.

I also understand U1900 is a communication failure between the instrument cluster, abs module, and the trailer brake controller. however, all these modules are in tact and work. I also went through the cars inbuilt test cycle and all it did was prove the instrument cluster works perfectly.

Any help with this will be much appreciated.

 

DTC U1900 = CAN Communication Bus Fault

DTC U1900 is not an actual fault. This generic code is usually caused by the diagnostics itself and should be ignored.

Any ideas on how I can fix this? I'm tempted to buy a working second hand ECU set, including cluster, key, receiver and fuse box. For 80 quid I think that's somewhere to start.

U1900 is one of the handful of codes on my 2010 mk2 at the moment. It doesn't seem to affect the operation or driving of the vehicle at all, as JW1982 says. When I've cleared codes, this one stays (or maybe comes back immediately after being cleared). Have you had any garages look at all? Also is it keyless or not?

Unfortunately unlike your car, mine will not start or turn over, nor will the immobilizer light turn off/dis engage. I'm not too keen on sending to a garage as the cost will rack up quickly overtaking the value of the car. The car isn't keyless.

Are you using Forscan or just a generic OBD reader?  U1900 is a really common fault that doesn't usually affect anything, as others have said above.   You may have another code stored, but if it's Ford specific it won't be picked up by a generic reader.

Unlocking and locking is totally separate to the immobiliser chip in the keyfob.  I don't suppose you have another key to try in case this ones faulty?

I'm using a generic OBD reader, but its very extensive with information and settings. But I do remember a garage saying that a certain 'software' is needed to read extra Ford codes. unfortunately I don't have a spare key. However, I've performed the hidden test and received the following codes.

D900 Communication error

E200 invalid data for odometer

E197 invalid data for vehicle speed

E199 invalid data for coolant temp

E510 throttle position?

A103 antenna not connected (this is fine, I know this)

9318 battery low (fully charged since, no change and code still there)

9600 signal not received, damaged key

9601 incorrect key code

9602 invalid key format

9681 transceiver signal not received

I'm pretty sure these are the definitions to these codes, but I'm not sure what this means. sort of proves there's a communication error? too many of those codes sound like they shouldn't go together, like the key codes. I've called a few places and many have said that its the cluster, but how so.

When was the battery changed? Maybe it's just on the way out, but that doesn't scream to me that it would be the cause of the issue you're having. I would look more that those key related codes. TomsFocus says the immobiliser chip and unlock functions are different chips. Have a look at this video, this guy's key works to unlock the car but literally doesn't have a transponder for the immobiliser at all. 

I don't have my manual on me, but I'm pretty sure there's a section in there about re-pairing keys. Maybe take the key apart and check the connections in there. Might need a new key entirely, but I'd have a go at the re-pairing procedure or inspect the key first.

Update: thanks for the video this helped me realise when I changed the key Barrel, I swapped the internals of the old key for the new key, without the transponder. They car now starts and runs with the immobiliser disengaged. 
 

however, they problem still exists with the U1900. The code is still there despite the car running fine. On the dash I have 7 warning lights that are incorrect. For example hand brake and seat belt light, as well as airbags off. I’ve check all the connections and they’re fine. The footwell lights never go off and my head lights don’t turn on, only small day lights. When I go to to turn on full beam, it turns my headlights on, very dim too.

im guessing this is all to do with the U1900 code. Something electrical is going wrong? I did but the second hand ecu and cluster, but this changed nothing, same lights and problems. (I also got a key with it but I know now about the transponder and immobiliser so, steer away from this problem as it’s not a problem any more) 

 

what should my nexts steps be, I’ve read up about the problem and some accounts say the light doesn’t cause an issue for a while the suddenly one day it won’t start, won’t change gear or stalls, goes into speed limited mode and engine failure displayed and so on. I don’t want it to get to this but at the moment it’s running and driving. Not perfect but that’s just age related.

GEM module would be the next place to look.  The fusebox under the glovebox, it's probably damp or corroded inside.

A second hand fuse box came with the ecu and cluster as a set, I put this in and nothing changed, all the fuses work and relays are fine. I did find that the old fuse box was ever so slightly damp and read that it’s most likely the cold weather setting in, most of the inside was dampish. Regardless, that was the old on and neither that or the new one changed any problems unfortunately 

So you've changed both the clocks and GEM and have exactly the same faults on the new ones?  Have you checked the interior earth points?  One's near the pedal I think.  If it's not that, I suspect a loom fault which could be near impossible to find.  

I checked all the engine grounds but I didn't realise there was another inside, I'll have a look over the weekend.

I did manage to get the car into a garage for free, they had a look at it with their much more extensive engine reader with Ford specific software. There were 7 very random and unrelated faults, whereas mine only showed the U1900 code.

The faults were cleared and all the modules seemed to be communicating and working perfectly. There was one persistent problem though, the airbag module was unable to communicate with the PCM, this will explain the airbag light on as well as the engine light?

However, on face value, seems that nothing has changed after removing all the other faults (unfortunately I didn't get to see what they were but they didn't come back), most the lights on the IC are on and the U1900 code is still there. Seeing as random unrelated lights have been on the IC since the start, I thought nothing about the airbag light. would the airbags be causing this U1900 problem? but how is this related to the other lights on the dash, seatbelts and handbrake for example. I don't see how these will go off if I find the problem with the airbags, if there even is a problem.

Seatbelts are part of the SRS (airbag) system, so those are directly linked.  However, it sounds like a network issue with the CANBUS.  Wiring now doesn't just carry a little voltage to individual items like it did in old cars.  Modules are all liked with the CANBUS and I think you'll have a damaged CANBUS wire somewhere.  They're the twisted pairs in the loom.

There are definitely earth points inside for the clocks etc.  Everything in cars relies on a good solid earth.

Ok thank you for this, Ill have a look. However what's the deal with the handbrake light, I've had a look at the wiring for the handbrake and all seems to be fine. Advice from the garage is to test the power and ground for all the connections for the airbags, seatbelts and handbrake. As this is seemingly going to be the issue, and just visually checking wires wont give enough information.

Sorry, haven't logged in in a few days. Really glad you got the immobiliser issue sorted, but unfortunately now a whole host of other issues. My knowledge of the dash lights and console is next to nothing, I've really only worked on the engine and happened to see that transponder video. I think TomsFocus will be your best bet here. Sorry I can't help any more!

Not sure I can take all that responsibility!  

The handbrake light is also the low brake fluid light, and I think it runs through the PCM...so again, part of the network and not simply a bit of voltage from A to B. 

With those faults I really would suggest finding all of the earths around the dash, you'll need a decent wiring diagram for this though, I don't know where they are.  

I'd recommend getting Forscan so you can read your own Ford specific faults instead of the garage kindly wiping them all without noting them so we have no idea what they were.   

If the airbag module isn't communicating then the first test is to check the module itself is getting power.  Second test is to check the CANBUS wiring between the module and whichever module reported the loss of communication (probably the clocks?).  However CANBUS wiring tests aren't just simple voltage tests, so you'd need to do some Googling on that.  It's not really my area I'm afraid.  What are the exact lights and warnings you have on the dash currently?

On 11/18/2020 at 3:06 PM, haz20 said:

Hi everyone, I have a Ford Focus MK2 2005 2.0 and I've had the U1900 engine code pop up and I've tired everything to get rid of it. Its been on for a while but I haven't been driving for a while either. i drove it for a couple mins up and down the road with the light on and it was fine. only a couple days later it doesn't start and I have the immobilizer light flashing giving the code 14. I read this is irrelevant when the U1900 code is present. which I believe as the car recognizes the key as it locks and unlocks. Id love any input on this. to save time, the tings I've already done are as follows.

- Re-soldering the instrument cluster, no change

- Cleaned up all the ground point to bare metal 

- Re-charged the battery over night

- Tested the PCM/ECU and a solid 12v power is present when the key is turned

- Ensured all wires were in good condition with no cracks

- Also that all the connectors were in tact

- All the fuses and relays are fine and work

- Both fuse boxes have power

- Tried using the OBD II reader to clear the code but 'erase failed' is displayed

- Tapped the top dash a few times above the cluster 

I did my own test and disconnected the throttle body then turned the cars electrics on. The code reader then displayed two more codes, related to the throttle body as expected. speed limited mode and engine systems failure were also displayed. After connecting the body back to the loom the codes disappeared and only U1900 was displayed as before. I'm pretty sure this tells me that the communication between the cluster and PCM is fine? On the other hand I've had both speed limited mode and engine system failure displayed before when just starting the car but it disappeared. is it possible the U1900 is related to the throttle body now? how would I test this or other components. everything has power and all connections and wires seem real fine.

I also understand U1900 is a communication failure between the instrument cluster, abs module, and the trailer brake controller. however, all these modules are in tact and work. I also went through the cars inbuilt test cycle and all it did was prove the instrument cluster works perfectly.

Any help with this will be much appreciated.

 

Have you tried to clean all the earth points under the battery tray? My focus wouldn’t start so I cleaned them and it sorted lots of faults! I have an ABS communication issue so am still trying to sort that! 

U1900 is a loss of communication error on the HS or MS can bus. It can be intermittent  and not show on a instantaneous test.

both can busses route through the cluster and failing solder joints is not unheard of.

usualy accompanied but other spurious faults which use that can bus.

whacking the dash above the IC did react on ours but some have had to remove the cluster and flex the connector, engine running of course.