U0121 Fault code

Hello all. First time on a forum and a newby to the world of Freelanders. I am hoping someone out there can help me out on this one. I currently have a dead Freelander 2 automatic, 2007 2.2 Diesel on a 57 plate. Coming home the other day I had a warning HDC Fault and the speedo stopped reading. Engine ran normally and as I was only a mile from home kept going.When I got home and tried to re-start I had a HDC fault code and the engine did not turn over. I have checked the brake switches, checked all the earths, visually inspected the wiring as best as possible, tried 3 different battery's, done a hard re-set. My code reader had no faults apart from a U0121 which is a loss of comms with the ABS unit. Voltage to centre HDC controls is also ok I have voltage on the supply to the ABS, all fuses and relays tested. I connected the starter solenoid direct to a battery and the engine cranked so the starter and solenoid is ok. Am a sparky by trade but this has me beaten. Any help/advice would be really appreciated

If you have power to the ABS module, check for voltage on the CAN bus high and low. One should be slightly higher than the other around 2.5V, exact voltage can be found out.
Not sure of the colours, but I think they are a twisted pair to the modules
You could check the resistance between can h + l, which should be 60 ohms
Also check for open circuit from the can data pair to earth
As you have no comms to ABS unit, I'd check data to the unit.
Poss can bus to earth somewhere or cable non continuous.

Hi J_D. Many thanks for the help. I tested the CAN Bus high out and you are correct it is a twisted pair, white and blue/white. I had continuity from the central junction box and voltage of 2.7V on the CAN C+ (Blue/White) and 2.4V on CAN C- (White). I also had around 60 ohms resistance. I compared this to the central switch CAN bus which also read the same. I am fairly sure the issue now lies with the ABS unit its self. This leads me to ask if anyone knows if you can test the ABS unit its-self in situ with out having to remove it first and disturbing the brake system . I will also then need to look at whats involved in obtaining a unit that will work on my landy, as I had the same issue with a mini and I was told MINI would have to supply and programme and fit, they quoted over 2K , the mini was only worth 1.5K !!!!!.
Many thanks for you help so far I really appreciate it.

Just to be sure, you deff have 12v and an earth on the correct pins?
I don't have a wiring diagram, which pins have you the incoming voltage?
Can you clear the code to make sure its not an old stored code?
If it is the abs ecu, it looks like its coded to the vehicle. You could try bba reman to check/repair your unit.
To replace, it would need bleeding through the ABS pump, which would require diag equipment capable to run the abs pump. It would be an investment for any such diag equipment especially if it does other cars for you.
Try posting in the Freelander section for more views and helps.

J_D said:

Just to be sure, you deff have 12v and an earth on the correct pins?
I don't have a wiring diagram, which pins have you the incoming voltage?
Can you clear the code to make sure its not an old stored code?
If it is the abs ecu, it looks like its coded to the vehicle. You could try bba reman to check/repair your unit.
To replace, it would need bleeding through the ABS pump, which would require diag equipment capable to run the abs pump. It would be an investment for any such diag equipment especially if it does other cars for you.
Try posting in the Freelander section for more views and helps.

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Hi sorry for the late response work got in the way. Thankyou for responding I appreciate your help. I have a diagram and all the voltages are good. The negative back to the battery has negligible resistance so I know that's good. I think there is multiple issues as I have also found the steering lock has no 12v feed from the central unit. Fuse is good and have continuity through the board. I have bitten the bullet and ordered a iCarsoft CR PRO Advanced Multi Vehicle/System OBD2 Diagnostic Scan Tool so will look into it next week when it turns up and I can get back to it. Will update when I get to the bottom of the issues as it might help others here. Many thanks again.

If the ABS module has failed, you'd have been better off getting SDD software and a Mongoose cable, as this will be required to configure a replacement ABS module to the vehicle.
If it's not configured to the vehicle, then the engine won't start.