Technical ABS intermittent fault

[The Panda Nut]

Our mylife 2011 69 HP car has decided to start misbehaving. The ABS and brake fluid / handbrake lights light up for no apparent reason. When the ABS light is on the system certainly does not function but the car pulls up straight and true and lock the wheels together. Turn off the ignition and it resets OK but will come back on - and go off at will.

ECUScan shows no faults and you can hear teh ABD pump fire up when tested even when the warning light is on. You can hear all the solenoids working too.

The system is full of fluid and has been working fine. The car is used almost every day.

Any suggestions? Thanks.

 

[koalar]

ECUScan ? same as fiat ECUscan

is that just for the engine module ?

can you select the ABS module ?

I have only managed to connect to the ABS with multiECUscan, WOW and delphi

MES need different leads though

Flat tyre or faulty abs sensor would be my guess. Gets to a certain speed an does a self test. Spots a difference and flags a error code. Getting something to read the abs properly would be the first port of call

 

[The Panda Nut]

Its registered Gendan Fiat ECUscan with all the correct leads. Green adapter as required. I guess your right about a sensor being most likely. I cant do the work at present or I would take them all out and clean for starters so I will have to hope its not mega job. I am having the dealer look at the whole system as the pedal is getting low. It may need pads and discs and is due for a fluid change. I am just surprised software is not seeing a fault with the light on. I can get the abs module and have run all available tests and all seems OK. ABS works fine with the light off which it is mostly but not when the light is on. Tyres are all normal but I will look at them again. I may try all my adapters in case the instructions are wrong...

 

[koalar]

If you can see and connect to the module thats fine


Not sure if its an option in FiatECUscan but if you can turn the pump on and off it must have proper two way communication by the software


strange it doesn't see any logged or pending codes. There will be no current codes as its being reset. I have a faulty motor to fix at the moment. That shows all the time as it solid fault and shows up in all versions of software. Not had an intermittent error on ABS but I would expect it to store the code the same as the power steering does.

how High do you have to pull the handbrake on. It shouldn't be more than 5 clicks if its too much the brake pedal travel is longer than normal ?

 

[portland_bill]

ABS systems are generally very reliable. The weakest parts are the speed sensors, and the reluctor ring that they read.
Easy start, do a physical check of the sensors, and their wiring. A wire that is broken inside may only fail when flexing, giving the intermittent fault.
More difficult is to check the reluctor rings, as these are part of the bearing seals. Dirt or corrosion can affect them.

If no codes are stored, this suggests that the system is getting a reading from one wheel that does not match the rest, but is otherwise not a 'wrong' reading. A broken wire should flag that sensor as a fault, but dirty reluctor or sensor may just give a reading that is intermittent, enough to suggest one wheel is turning significantly different to the others.

 

[The Panda Nut]

how High do you have to pull the handbrake on.

Its all normal 3-4 normally and 5 clicks for a really firm hold. I cant see anything on MES referring to sensors at all. I have test run the pump and solenoids and all is reporting as normal. I suspect its a dirty sensor but cannot currently look myself. Hopefully it will found quickly if this is the case. Had something similar on mums Perodua a few years back. Removing and cleaning did the trick on that and the wheel sensors were MEGA rusty.

 

[portland_bill]

Set MES for live data and go for a gentle run, hopefully with someone watching the numbers. All four wheel sensors should give similar numbers, with differences for cornering, different tyre wear etc. Hopefully will show when one suddenly goes haywire.

 

[koalar]

pedal getting low is worrying


have you tried the bleeding the bakes


if its not air in the system, handbrake adjustment its normally the master cylinder.

 

[The Panda Nut]

Well its gone in with instructions to do a full brake service with a change anything that's required addition. The ABS fault was not evident over the 15 mile trip as ever. We will see what they do! I asked them to remove and clean all the abs sensors too.

 

[The Panda Nut]

Well they did a full inspection and diagnostic and checked all the things MES checked with the same result. No faultsnshowing Apparently removing the fluid level sensor wires did cause the same issue but did not flag a code in the ECU so that sensor is prime suspect. It costs £28 + fitting so its going back next week to be done and will take about 45 mins with a brake fluid change. The diagnostics and checks cost £100 which is a lot, but fair. You can't mess with brakes and I am not currently fit enough to do the job so poorer but content daughters car will be safe.

 

[The Panda Nut]

Blasted thing is doing it again. Its just been cleaned up to be sold too . Just driven up the road and the ABS is working so hopefully just that sensor again. Its definitely time to move it on. I want to do other things than chasing this one about. I have only just got the engine EML off after a wobbler. In that case new plugs sorted ot out. Cars should not need new plugs after just 8000 miles. I shall plug it in in the morning and see if there are any faults visible. At least I have an idea of where to start.