Fiat Bravo ABS failure - what to check?

The message from "Hellraiser" contains these words:

Brake lights.

???? Will that really freak out an ABS system???

Hellraiser...........>

Hellraiser ( snipped-for-privacy@nospam.blueyonder.co.uk) gurgled happily, sounding much like they were saying :

Not normally, no.

I s'pose that Fiat might have put some wierd ABS system on that incorporates a brake-light bulb failure warning, but...

Still - for the amount of time it'll take to rule it out, it's got to be worth a check.

If the light is on at engine start without the car even moving, then 9 times out of 10 its a wheel sensor short or open circuit.

Tim..

Wheel sensors seem to be the most common cause for ABS faults. Mike.

The message from "Hellraiser" contains these words:

Yes, on some systems. Some use the brake light switch to detect that the pedal's been pushed, and without the load on the line, the voltage doesn't go up and down when you press it.

Cheers all - thought I'd sorted it cos it went off yesterday, but came on soon as I started moving, so I guess I got a dodgy wheel sensor. Any way to find out which one, short of giving Fiat 30 folding for a diag check?

Hellraiser...........>

Basically the sensors are small magnets surrounded by a coil, so as the toothed ABS sensor ring spins, a current is generated. With a DVM, check each one for resistance. Dunno what the actual readings should be for your car. They could be anything between 600 and 2000 ohms, but obviously the two fronts should be the same, and the same for the rears. Set the DVM for volts and spin the wheel. You should get a reading of 50-700 MV. Check the contacts in the plug are clean, and also the sensor rings. Excessive brake dust can also cause ABS faults to show. Metallic particles can get stuck to the magnets in the sensors. If all sensors check out, maybe it's time for a visit to the dealer as the fault could possibly be in the ABS modulator. Mike.

In article , Hellraiser writes

It did on my Cavalier. Couldn't believe it either but it did.

Thanks for this Mike, when my hangover has worn off tomorrow I'll start getting wheels off! Just wondering if that hooky copy of Autodata will tell me which pins to check....

Hellraiser...........>

Hi Hellraiser

Just a word of warning. Taking the wheels off may not help you much.

Normally the sensors come with a continuous lead and end plug, i.e. no plug on the sensor end!

The plug/connector to the car witing loom is INBOARD of the vehicle. Trace the wire from the sensor into the bodywork. If no connectors are found enroute then the connecotr will be found just inside the car, normally withing six inches of where the sensor cable enter the Bodywork. This will almost always be in an expected dry area. Often one has to dig behind the internal trim to find the connector.

Nick /////

Cheers for that Nick, as and when the hangover clears I'll have a forage :)

Hellraiser..........>

Wow. Done nothing to this car for a fortnight (was gonna drop it in for a diag when I got chance), hit a speedbump and the ABS light went out. Been working fine ever since!

Who says speedbumps are bad :)

Hellraiser............>

Me! Car passed it's MOT yesterday with 2 advisories (sp?).

Front shocker, and anti-rollbar bush split, drop link damage. You can put is down to speed numps and potholes, both of which exist in large quantities round where I live.

As an aside, anyone know why exactly Kwik-Fit aren't allowed to do the front shockers on Bravas? (Not that I was going there, but wanted to price it, so I could haggle with somewhere else).

Presumably 'cos they might have to do some work to change them :) Avoid Kwik Fit, they quoted me over 200 quid to sort out a duff brake hose on a Punto, saying it would have caused the caliper to stick on (!), which would have worn the pads and most likely the disks..... yeah right, 10 quid to Fiat for a pipe and 20 mins work, sorted :) There's nothing unusual about the shocks on a Bravo/a, go to someone with a clue :)

Hellraiser............>