Came to have a drive out the other day and noticed the ABS light had come on on the dash. Is this a garage job or is there anything I can/should check? I guess it is something to do with the sensors…
Any suggestions will be most welcome. Also, with the light on, would that be an MOT fail? Thank you
Most likely a front wheel speed sensor. If you’re handy around a car you could replace it yourself. Check the resistance of each one to confirm the fault. Expect rusted bolts to break off during replacement
An ABS lamp illuminated is an MOT failure I believe.
Thank you for your initial reply.
Just had a read of the general info on the ABS in the Haynes manual - all sounds quite technical and involved! It runs through how to access and remove the sensors on the front and rear wheels. Point 11 on the front wheel sensor states ‘ensure that the sensor and hub carrier sealing faces are clean, then refit the sensor to the hub’. I would not know how to check the resistances?? In the manual, it refers to the hydraulic unit and straight after that, the ECU. You don’t have to disconnect/remove that to do these checks on the sensors do you?
You can unplug each front wheel speed sensor from under the bonnet and check the resistance from that plug. Do you have a multimeter?
I have a similar issue with my ND, very random and haven’t got to the bottom of it. Dealer did the usual diagnostic check but as luck would have it they checked it when the light wasn’t on and no codes had been recorded. I left it and drove it over the summer with a few instances of it but sods law emerged come MOT time and as he reversed off the ramp about to give it clean bill of health you can guess what happened next 
(yes it is a fail) Tester had a quick look but wasn’t too keen to go down the rabbit hole of sorting random faults so did a quick diagnostic check, a run round the block after clearing the codes and the light which didn’t come back. Car is now sorned and I will have to dig deeper in the spring but the MOT tetster said it may be an ABS or wheel speed sensor that needs replacing.
I hate random electrical faults!
On some Japanese cars the ABS warning light also indicates brake lamp failure, includng LED “bulbs” with insufficient resistance.
Not Japanese but my kid’s 2002 polo also had an intermittent ABS failure light. After lots of diagnostic codes, I was told it was a power failure and would require a new ABS unit.
A google search of the code was a small crack in the ABS fuse . I checked that and there it was, a tiny hairline crack in the fuse. Replaced for 14p!
Maybe, just maybe……
Is there a fuse that governs (or is in the circuit for) the ABS light?
No, there is no separate specific fuse for the ABS lamp.
Having watched a few Youtube videos, I can see that there is a ABS/wheel sensor on the front and rear wheels. ( 4 in total). Quick check - is an ABS sensor and a wheel sensor one and the same thing?
If yes, then would it be worth trying to remove each in turn and carefully cleaning them at the sensor end?
Robert (Roadster_Robbie) - you say I could check the resistance of each at the plug ends (via an open bonnet). I do have a multimeter so could you possibly explain in detail how I would do this? Many thanks
Just had the car jacked up on nearside front and located where the sensor is attached to the hub and also where the plug is within the engine compartment. That was the straightforward bit! The plug in question is attached to a covered run of wires with a strong ‘tie’ and also tucked down almost under a black vertical ‘plate’ meaning two hand access is rather limited! Couldn’t open the tie, so ended up carefully cutting it. Next problem - can’t separate the two plug halves…looks like there’s a central tab that needs to be pressed in but it’s flippin difficult to do that and try and pull the sections apart at the same time.
In terms of fault diagnosis, can anyone recommend an ABS sensor reader device that I could potentially purchase that will reveal fault code(s) and which wheel is giving the problem? Any help is much appreciated, thank you.
You’re nearly there. You do need to disconnect that connector though. Try pushing it together slightly before pressing the lock tab, then pulling it apart. It’ll be tight but it will come apart.
Once you have it apart set your multimeter to the Ohms setting ad connect the leads to the appropriate sockets. Touch the leads to the terminals in the plug that go to the sensor, it doesn’t matter which way round. If it’s an auto-ranging meter it’ll just show a reading if it’s manual ranging you’ll have to switch the range. Start with the highest then work down until the meter goes over-range then switch back one click. You’re looking for around 1.5 kilo ohms for a good sensor.
Does this photo help at all?
Each sensor (front, rear, left & right) can be tested in the same way.
This is a link for how to check for fault codes in the ABS system.
Changing the senor will be a pain, bolts will be rusted and will break off when you try to remove them and the sensor itself will be seized in the hub and reluctant to come out. Make sure that you remove any rust from the sensor mounting hole prior to fitting a new sensor. It needs to be a “sliding” fit and not tight.
ABS sensor and wheel speed sensor is one and the same.
Hi Robert, thanks so much for your reply. When the weather next allows, I will persevere with trying to separate this first connector and, assuming I am successful, do the resistance test. Do you need to the voltage test as well? If, on the resistance test, you get around this 1.5 kilo ohms, are you safe to assume that the sensor itself is fine and therefore don’t need to remove and replace it? With multimeter working correctly and you get no reading (zero), then I guess the sensor itself must be bad? Will my car be fitted with passive or active sensors?
I have read the link you gave me for ABS fault code reading but don’t fully understand it. Will following those steps reveal the code(s) relevant to my vehicle on the dash? Do you not need a fancy (expensive?) ABS code reader? Not sure what that image is all about…
Sorry to fire all these questions at you! Thank you
Robin
No need to check for any voltages, just check resistance through the disconnected sensor. If you get the correct resistance then the sensor is probably OK. If you get a reading that is significantly high or lower than 1.5 kilo ohms then the sensor is faulty. Your car has inductive type sensors which is what I think you are referring to as passive in that the are not supplied with a voltage to work.
Fault codes can be read by following the procedure in the link and observing the ABS lamp flash codes. This tool may work for reading ABS DTCs but check with the vendor first if you fancy treating yourself.
The photo is just an example of the right hand front ABS sensor being tested with a multimeter. In the example the sensor is open circuit, that particular meter displays “OU.CH” in that scenario. The photo was more about the connection method.
Sorry, no, it was the image that comes up when you click on the ABS fault code reading article, nit your photo!
It would appear that diagnostic device from mx5tech is currently not available. Wonder whether this would be suitable?
Autel AutoLink AL619 Code Reader with ABS/SRS Diagnosis — OBDPRICE
The image in the link is a diagram of the DIAGNOSTIC plug terminal layout that is under the bonnet on the passenger side.
No idea on the Autel product sorry. But honestly, I’d use the flash code method and save my money.
Morning. Been under the bonnet again trying the separate the two halves of this nearside front connector but just not getting anywhere. Can’t seem to get any obvious movement in the lock tab, plus access is difficult. Debating whether to try and cut this lock tab off and/ OR cut back the protective stiff black tubing to reveal slightly longer lengths on the incoming black and white wires, then cut them. This would enable me to put the probes on and test. Would obviously have to solder them together again afterwards and tape up/heat shrink. Thoughts on that approach?
I wouldn’t cut them. How about using a small flat blade screw driver to lift the tab from the front.
Might be worth doing a fault code read to potentially give you some idea of which sensor maybe at fault rather than disconnecting them for no reason given that you’re struggling with this. Just use a bent paper clip to short the relevant terminals out in the diagnostic connector the turn the ignition on.
OK, so follow the guide you linked to and push one end of the clip into the TBS and the other into the GND terminals? It says turn the ignition on and ‘count the groups of flashes on the ABS light’. So these flashes - be they long or short - will come one after the other, will they? Why do you have to count them? What happens if you don’t? When the flashing stops, has it effectively finished the checks/tests?
Will one or more of those DTC’s show on the dash? Will pressing the brake pedal 10 times clear the fault(s) and thus the ABS light will go off??
Yes, bridge TBS and GND terminals in the diagnostic connector and turn the ignition on. Be sure to bridge the correct terminals.
The ABS lamp will flash if any fault codes are stored, for example a code 14 will be one long flash followed by 4 short flashes. Leave the ignition on and keep monitoring the warning lamp. Once all of the codes have been output (if more than 1) the sequence will start again on a loop. For example if you have codes 13 & 14 the light will flash 1 long flash, 3 short flashes, then 1 long flash then 4 short flashes then 1 long flash then 3 short flashes etc. The flash code(s) can then be cross referenced with the list in the link. Once all of the codes have been flashed and the pattern repeats, press and release the brake pedal 10 times to clear the codes. The light will probably stay on constantly. Turn the ignition off, remove the jumper wire then start the engine. The ABS light may remain off or it may come straight back on or may come back on after driving (wheels turning). If it comes back on, recheck for fault codes using the jumper wire and then go from there. This may give you some idea of where the fault lies.
