Hi,

Our 2010 (2011 model) Smax 2.0 has suddenly developed an issue. 

First thing that happened was the alarm went off in the night, when we went out engine was off but dash etc all on and it wouldnt power off. No response from the start/stop button and no response to keys fob. The only way to shut it down was to disconnect the battery (new in April 2025 & all fine)

Called AA who found a load of fault codes - including several U codes.(Same codes on our tester too) Checked all fuses and obvious areas, then suggested it may be a BCM issue & to contact garage for options. Ford quoting £1300! if it was just the bcm (more if not!) to sort.

So as another option we've had the bcm cloned to another (tested as working) bcm but, the issue is still the same. 

Checked resistance on can bus and reading at 62 ohms, and Voltage appears ok. 

Currently checking the grounding.

Has anyone any other ideas what it could be or what to look at next?

Don't want to spend 000's on a 60 plate car as not worth it!

5 hours ago, luzzieuk1 said:

Checked resistance on can bus and reading at 62 ohms

There are two separate Canbus systems on your car. Did you check both the Medium Speed, and the High Speed ?

Is the car an Automatic ?

I am interested in this one.
With the obvious multiple issues, I'd ask for the list of codes to see if there's anything that points to the source.
Assume they have been cleared, what returns?
Agree with the above i.e. there are two networks and U codes are communication issues (with which modules)?
If the other network doesn't give the 62 Ohms then that needs looking into although it could still be a modules that doesn't have a terminating resistor?
Is it always the same i.e. reconnect battery, alarm goes off again?
Are we using Forscan to ensure all Ford specific codes are being registered?
One way, if the symptoms are constant would be to disconnect modules to see when the issues stop or change, the alarm module, perhaps the first?

8 minutes ago, Shearers said:

although it could still be a modules that doesn't have a terminating resistor?

the canbus has two 120 Ohm resistors one at each end, in parallel.

44 minutes ago, unofix said:

the canbus has two 120 Ohm resistors one at each end, in parallel.

Whilst there must be two modules with terminating resistors at the ends, there are likely more than two, in total, in a network so some won't have any?
Presumably (I don't know) if the resistance was 120 or zero, the relevant modules would be missing or damaged.

I'm unsure what happens on the network if the faulty module is one that has a terminating resistor (I'm by no means an expert but always ready to learn)?

2 hours ago, Shearers said:

Whilst there must be two modules with terminating resistors at the ends, there are likely more than two, in total, in a network so some won't have any?

Hi Shearers, you are correct most modules don't have the terminating resistor fitted since they are connected to another module either side. The system is a loop, a break anywhere in the loop will result in the resistance changing from 60Ω to 120Ω see the little diagram attached which probably demonstrates the system better than me trying to use words.

On 1/22/2024 at 10:52 PM, unofix said:

The Canbus resistance should only be measured when the ignition is 'off'

Measure between pin 6 (can Hi) and pin 14 (can Lo) it should be 60 ohm

No other reading are of any importance with regards to the canbus network.

I can see that you have a reading of 63.6 ohms which is only just out of normal range (max 62.0 ohm) but the extra resistance could be either just your meter leads, or you were not getting a good contact.

On the bases of your reading it looks like the canbus end of line resistors are both connected correctly.

 

15 hours ago, unofix said:

There are two separate Canbus systems on your car. Did you check both the Medium Speed, and the High Speed ?

Is the car an Automatic ?

Hi,

Thanks for replying. 

We have checked both the MS and HS sides and both at 62ohms. Yes, it's an automatic.

15 hours ago, Shearers said:

I am interested in this one.
With the obvious multiple issues, I'd ask for the list of codes to see if there's anything that points to the source.
Assume they have been cleared, what returns?
Agree with the above i.e. there are two networks and U codes are communication issues (with which modules)?
If the other network doesn't give the 62 Ohms then that needs looking into although it could still be a modules that doesn't have a terminating resistor?
Is it always the same i.e. reconnect battery, alarm goes off again?
Are we using Forscan to ensure all Ford specific codes are being registered?
One way, if the symptoms are constant would be to disconnect modules to see when the issues stop or change, the alarm module, perhaps the first?

Hi, thanks. 

We do have the code list, AA sent us them on their report. We also checked with the fault reader we have - its not Forscan but is set to be ford specific, comes up with same faults the AA did. 

The alarm hasn't gone off again since the first time, we originally got it to stop with the key fob but the car wouldn't power off - still won't if battery connected. Key fob now only works on the boot unlock button, won't work on central locking.

These are the fault codes:

U001088
U010100
U012100
U020000
U045200
Central electronics -5B9 /central electronics
ZE G9.0B10A202 - Impact sensor error
Malfunction - B10A215- impact sensor
B10EA- additional heater error

The faults won't clear.....

When you say disconnect each module, is that via its connector to the bcm?

The U codes are all communication errors and appear to apply to the Medium Speed Can Bus as evidenced by:
https://www.aboutautomobile.com/Diagnostic-Trouble-Code/U0010-88
This isn't a specific Ford code but seems to apply to multiple makes as a generic OBD code ("WE" would still say likely better to use Forscan to get any Ford specific information?)
Maybe TCM as it is auto
https://www.engine-codes.com/u0101.html
And ABS:
Code: U0121
Title: Lost Communication With Anti-Lock Brake System (ABS) Control Module

Passenger door module:
https://www.obd-codes.com/u0200

Restraints control module:
https://www.engine-codes.com/U0452.html
ETC!
All related to MS-Can Bus?

Based on various Techs I follow the process is to disconnect the individual modules from the network until the fault clears. If there is still an issue then there's likely damage to the twisted pair wiring that the CAN signals are sent on.
Dan appears to have had a similar issue?:
https://www.youtube.com/watch?v=uKnQI2IScPU

The PCM is under the wing and this is a common source of wiring issues.
To me, it looks like a competent auto electrician may need to be involved?

Edit: and if it's the ABS module, don't panic, you can get it repaired with a lifetime guarantee:
https://www.ecutesting.com/

Have a VERY good look at the TCM connectors on the gearbox. You may have to unplug them and remove the back shell of the plug. Look for damaged/corroded wires and check the pins of the connectors for signs of water ingress.

The wiring harness is often very short to the TCM and it causes a lot of strain on the connectors and can lead to the wires rubbing through the insulation.

And please let us know!

Don't just stop responding unless we all give up!😉

Big thanks both. We will start trying those areas and see how we get on.

Diagnosedan very informative so many thanks for the link.

Will come back soon!

On 12/19/2025 at 6:29 PM, Shearers said:

I am interested in this one.
With the obvious multiple issues, I'd ask for the list of codes to see if there's anything that points to the source.
Assume they have been cleared, what returns?
Agree with the above i.e. there are two networks and U codes are communication issues (with which modules)?
If the other network doesn't give the 62 Ohms then that needs looking into although it could still be a modules that doesn't have a terminating resistor?
Is it always the same i.e. reconnect battery, alarm goes off again?
Are we using Forscan to ensure all Ford specific codes are being registered?
One way, if the symptoms are constant would be to disconnect modules to see when the issues stop or change, the alarm module, perhaps the first?

Hi, thanks. 

We do have the code list, AA sent us them on their report. We also checked with the fault reader we have - its not Forscan but is set to be ford specific, comes up with same faults the AA did. 

The alarm hasn't gone off again since the first time, we originally got it to stop with the key fob but the car wouldn't power off - still won't if battery connected. Key fob now only works on the boot unlock button, won't work on central locking.

These are the fault codes:

U001088
U010100
U012100
U020000
U045200
Central electronics -5B9 /central electronics
ZE G9.0B10A202 - Impact sensor error
Malfunction - B10A215- impact sensor
B10EA- additional heater error

The faults won't clear.....

When you say disconnect each module, is that via its connector to the bcm?