Scania ABS fault

[Muz]

For a while .. I'd been getting an intermittant ABS light appearing on the dash. Hmmm .. I thought not good news and a bugger to trace sometimes. What could it be ? .. well Ive six wheels on this rig which is a 2006 model. The dash computer logged a series of ABS faults which my dealer helped by deciphering the codes, to see what they meant.

I had already surmised that the fault only appeared after the tag axle was lowered, and run on for a few miles. After about 60 miles of service it would often go out, so clearly once it had warmed up. The way Scanias are wired means that when the ABS fault lamp is lit .. it also knocks out the exhaust brake which is a PITA since its very useful when fully loaded, and assists the braking effect very well, preventing the brake rotors heating up too much.

Fearing the worst, I thought it was going to a real tough one to resolve, and as you will all know, features some quite expensive componentry in the ABS system, controllers, sensors, footbrake valves, servos .. you name it.

Well .. always remember rule #1 of spanner work ...always check the simple stuff first

[ianoz]

Hummm, something as simple as a loose wire ,or plug ?

[Muz]

Easier than that even ! .. It seems these ABS sensors are magnetic, and I assume there is a tiny reed switch in the sensor. It would operate by the serrations on the disk rotor making the switch trigger, every time a serration passes across it, thus, the 'brain' can observe differences in speeds of each wheel. On this caliper, the sensor is a push in unit, about an inch long, and about 3/8s diameter .. all that had happened was a piece of swarf was sticking to the end of the sensor causing faulty readings damn I wish they were all as easy as that

[ianoz]

Good to hear it was an easy fix Muz .
Wonder how long it would have taken the dealers guys to work it out .

[Muz]

Good to hear it was an easy fix Muz .
Wonder how long it would have taken the dealers guys to work it out .

Well .. I am a cynic .. what you would have got was a 'an excuse' and a bill for £1000.00 which most corporate customers would pay without the blink of an eye .. Its no wonder these dealers make so much .. but of course .. they blame the fact that they make no margin on the sale of new vehicles .. yet more lies .. and the trade ins

[Dan]

I heard the Renfrew bunch have a new Scania approved supplier line for recon stuff like calipers which you mentioned elsewhere ? steering boxes etc or atleast some agents do ?

post edit............. cant find em gogle but deffo saw a leaflet in work last week , ill digg it out and report back

[v8druid]

Easier than that even ! .. It seems these ABS sensors are magnetic, and I assume there is a tiny reed switch in the sensor. It would operate by the serrations on the disk rotor making the switch trigger, every time a serration passes across it, thus, the 'brain' can observe differences in speeds of each wheel. On this caliper, the sensor is a push in unit, about an inch long, and about 3/8s diameter .. all that had happened was a piece of swarf was sticking to the end of the sensor causing faulty readings damn I wish they were all as easy as that

I think most ABS sensors work on the hall effect system, don't they Muz, generating a minute electrical pulse - the serrations/castellations on the rotor, function as the intermittent air gap required?

The ECU then amplifies the signal from each sensor and analyzes the wheel/rotor speeds accordingly, comparing speed, relative to each other and also makes allowances, within given/predetermined parameters, for the differential effect on corners of the inside/outside wheels on the turn radius.

Bloody clever - as long as they're working - PITA when they play up. IIRC something like 90% of ABS faults are sensor related

[Tractortech]

Now Then..
I had my fault diagnosed by a Scania dealer, "rear axle sensor" he said. It turned out that corrosion had occurred inside the sensor retainer and caused it to split then the sensor fell from its perch so to speak. Wheels and drum off, massive hose clip on, drum and wheels back on. Then away to Devon for a combine that afternoon. Still running a treat 4 years on :-)

[v8druid]

Now Then..
I had my fault diagnosed by a Scania dealer, "rear axle sensor" he said. It turned out that corrosion had occurred inside the sensor retainer and caused it to split then the sensor fell from its perch so to speak. Wheels and drum off, massive hose clip on, drum and wheels back on. Then away to Devon for a combine that afternoon. Still running a treat 4 years on :-)

That must've been one hell of a jubilee clip