ABS fault with no fault codes

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DanClarke said:
Well, if the ECU has been swapped out, and the brake switch looks "iffy" that's a cheap thing to change (but I thought it was more to do with the Cruise/Control than ABS).
The High/Low pressure switch has been known to fail on the ABS. I have seen a few threads on forums about it.
Good Luck!
Click to expand...

On my model year there are 2 physical brake switches... One for the cruise control which has a 2 pin connection but also has a physical vacuum line attached to it to vent excess cruise control pressure. This is higher up on the pedal.

And then the second one which seems to be the same switch fitted to freelander, discovery, etc.. and has 3 pins with two internal switches for redundancy.

I've actually already replaced the 'top' cruise control brake switch as someone had busted the clips, so may as well replace the bottom one now.

Thanks for the tip of looking at the pressure switch... I'll take a look into that
 
Just checked my brake switches on the nanocom I think you said one of yours says open the other closed when I press my pedal both switches go from closed to open I’ve that’s right I’m not sure but it may help as for running the car up on stands I’ve done that and still got the lights on and no faults showing on nanocom I think all that will show is each wheel speed I’ve it helps you
 
Mines exactly the same there’s nowhere to look I’ve my nanocom can’t shed any light on codes I may check out the nanocom forum tonight see what’s said on there I will report back to you I’ve find anything good luck mate
 
pete12345 said:
Mines exactly the same there’s nowhere to look I’ve my nanocom can’t shed any light on codes I may check out the nanocom forum tonight see what’s said on there I will report back to you I’ve find anything good luck mate
Click to expand...

Thanks that would be really useful. Good luck to you as well :)
 
As has been mentioned, the dash message comes from the BECM so that is where I would be looking. Loss of communication from the ABS ECU could prompt the BECM to display the message but it would not produce a fault code. I would be looking for corrosion in the BECM connectors.
 
+1 on suspect BECM not getting data from ABS. Sensor air gap will be irrelevant with message at startup.

Also check the things like brake input, pump status, pressure switch inputs to ABS ECU via Nanocom Inputs menus. Might give a better clue.
 
Datatek said:
As has been mentioned, the dash message comes from the BECM so that is where I would be looking. Loss of communication from the ABS ECU could prompt the BECM to display the message but it would not produce a fault code. I would be looking for corrosion in the BECM connectors.
Click to expand...
This is a good point especially if there has been leaking heater orings.... Or in my case swimming!!!
 
Checked all (I think 21?) connectors on the BeCM and they're all clean as a whistle... not a visible trace of corrosion on any pin.
Reconnected the battery after checking and dealt with all the 'Window not set' messages and was then greeted with the ABS fault, which I was expecting.

I'm at a bit of a loss now... the brake switch is arriving today, which I'm sure won't fix the issue, but will fit it anyway for good measure.

I guess it would make sense for me to check continuity of the signal wires from the ABS ECU to the BeCM to confirm that there is actually an electrical connection for them to communicate with, i'll look at doing that later.
 
Good point - after I've fitted the brake switch and put the seat back in place I'll take it for a drive to allow the checks to finish and see if there's any difference.

Just to note, I've been reading on another forum (here https://www.rangerovers.net/threads/abs-fault.351667/) with very similar symptoms... Someone mentioned that the fault could actually be shown when reading the BeCM and not the ABS module itself...

@DanClarke when we connected your Nanocom, the ABS unit definitely showed no faults but the BeCM did have faults logged... I can't remember if we cycled through the whole list of BeCM faults or not though - there could be more in there!
 
domlinson said:
Good point - after I've fitted the brake switch and put the seat back in place I'll take it for a drive to allow the checks to finish and see if there's any difference.

Just to note, I've been reading on another forum (here https://www.rangerovers.net/threads/abs-fault.351667/) with very similar symptoms... Someone mentioned that the fault could actually be shown when reading the BeCM and not the ABS module itself...

@DanClarke when we connected your Nanocom, the ABS unit definitely showed no faults but the BeCM did have faults logged... I can't remember if we cycled through the whole list of BeCM faults or not though - there could be more in there!
Click to expand...
The BECM does not store fault codes
 
Datatek said:
It does not display the message normally, just the lights which as you say go out at 5/7mph.
Click to expand...
I thought the dash stored the last displayed message whether a current fault or not? If no fault, the message wouldn't come back with the next ignition cycle?
Might be wrong
 
Datatek said:
The BECM does not store fault codes
Click to expand...

Whether or not the BeCM itself stores codes, I thought that when using a Nanocom it presents as if you're reading the codes from the BeCM.

I don't own a Nanocom, but when @DanClarke connected his to my P38, the BeCM menus allowed us to see fault codes such as a P1668.

I am probably wrong, I've only ever seen a Nanocom in person once haha.

EDIT: I must be mistaken, as the PDF here shows no mention of reading fault codes from the BeCM... I must be thinking about a different ECU that showed me a P1668 code: https://www.nanocom-diagnostics.com/downloads/preview/p38-becm
 
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