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Discussion Starter · #1 ·
hi I was wondering if there's a list of ebs faults that people have seen and fixed on volvo trucks it seems to be a headache for many and a nightmare for most. I spend much of my garage hours on truck electrics of all breeds but volvo (renault where they are basically the same truck also applies) is the one I get asked about the most. strangely it is most often on I shifts.
I'll start the list with common fixes I've come across starting at the front of the truck.

corroded plugs in the front of the cab under the front corner panels this can cover many many problems.

wiring snapped, corroded, rubbed through and shorted out where cab hinges to chassis again many possible codes. also any where on the truck is possible.

splices in wiring absolutely anywhere in the truck -ve, +ve even shared can bus between several components these splices even when sealed from new can corrode break and cut through to other wiring, leading to all sorts of misleading fault codes.

on an axle they can have a new style ebs valve operating a 1990's abs valve on the other wheel, minor faults in either of these can lead to erratic data wrong fault codes etc.

multiple ebs valves on shared can bus wiring can also lead to incorrect fault codes for example you may have a fault code for axle two modulator but it may be dodgy wiring or even a fault on another axle

you may have fixed a simple fault but cannot erase the fault code with any diagnostic tool, try leaving the battery disconnected for a while and or take it for a test drive for a mile or so.

abs sensor fault, easy change it right?
ha ha, the holder may be corroded and not holding it at the right angle, the gap may be slightly out, the pickup ring may not be in good enough condition, cheap sensors aren't always good enough, testing the sensor with a hand held tester and spinning the wheel may say it's good but they aren't always accurate enough. small amounts of rust on the end of the sensor may upset it, there may be a nearly unmeasurable amount of slack in a wheel bearing.
Once a unit (an FH500) just wouldn't read a new sensor with a new ebs modulator fitted to the same axle every thing was perfect. I got fed up went home late that night after trying all I knew, I went back in the morning moved it out of the shed to do another truck and it just started working and kept working no idea why.

modulator faults are fairly common on these, usually just change them and all is well, valves can give erratic signals just like wiring faults, worth checking the plugs into them as well, a couple of refurbed modules have been faulty out of the box.

shorted I shift wiring and faulty components can play hell with ebs and the other way around so beware.

Finally Volvo's seem to rely heavily on all systems talking to each other so look at all fault codes on all parts of the truck. It is possible to miss a simple fault that may not be obviously related to what you are trying to fix.

any others I've missed of forgotten about please list below it may help someone or save them a small fortune.

Today i'm working on a 2008 FM400 4 axle mixer truck, it won't read any ebs brake pressures, modulator valves, wheel speed sensors. the I shift is full of fault codes, it won't change gear properly. the exhaust brake isn't working. the exhaust add blue system isn't working properly and is about to derate the engine because the nox sensor is telling lies, all these faults came up the same afternoon, (good luck trying to get vosa to believe you at a spot check with a list like that. honestly sir it all just happened) this may be a fun one!!
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