W210 ESP/ABS/BAS lights coming on at random times
 

Every now and again, maybe a few times a week, the ESP, ABS, and BAS lights will come on on my 98 E300. Sometimes just by shutting the car off, sometimes by shutting off and then turning the steering wheel completely in both directions, the problem goes away for days at at time.

Car is at my mechanic now to get it and a few other things looked at. My first thought is a bad steering angle sensor. Any other ideas?

From what I've read such things are very voltage sensitive. I wonder if I should replace the voltage regulator just for grins...it's original.

EDIT: Just heard from my mechanic...one of the control arms was completely broken off! Wonder if there could be a relationship between that and those lights coming on.

It may be something else, but when you first start the car, the system checks the ABS pump by briefly turning it on. If it does not start, those lights can be triggered. You can check this by having someone turn ignition on while you listen to the pump. You should hear it whirr. Problem is that brushes in pump wear and don't make proper contact. On my 98 E320, the pump cannot be disassembled - have to replace complete ABS/ASR pump and valving. I was lucky to find a good used ABS pump off a wreck and it is still working years later.

But your problem might be quite different. I am sure you have read about the brake light switch issue which many have (if not, check Benzworld W210 forum). Your control arm could be related if it affected the wheel speed sensor circuit which is part of the ABS system.

When I had those issues on my 96 E300 it turned out to be K40.

Wow...didn't know a bad K40 could exhibit those symptoms. I've often thought about replacing the K40 just because it's been in there for 18 years...maybe I should.

Mines been doing it for a long time. it does it off and on now for about 4 years. Who cares if it isn't causing a problem

If it were my DD that's probably what I'd do. But since it's my son's I wouldn't want him to be driving along in a storm and for all that stuff to become suddenly unavailable....which I assume is the case if the lights are on but perhaps not.

My 210 did this for a while, went through the usual bits, brake switch x 2, engine earths (worth checking as x 5), 4 x new speed sensors - it turned out to be a failing releuctor ring which couldn't really be seen.

Basically it snapped, with the broken part wedged under the speed sensor so remained hidden.

Replaced the voltage regulator but the problem persists. So my mechanic and I will investigate other causes.

Am I correct in my assumption that, when those lights are on, ABS, ESP, and BAS are offline? Or not necessarily?

If ABS light is on, find a slippery surface such as gravel or sand or snow covered road (we are supposed to have flurries next week!) and slam and keep the brakes on. If you get the usual ABS pulsing, then ABS is working.

Have you tried listening for the ABS pump to run as I suggested earlier? Easy to do and eliminates one possible reason for lights. Brake light switch is the other low cost replacement that could be problem.

Regardless of what is actually wrong, all the lights usually light up. If you get a scan from dealer or a shop that has full MB Star diagnostic capability, it will pinpoint problem more closely.

I'm tempted to replace the K40 just because it's cheap and easy.

I second the reluctor ring, maybe just rust or crud on it.
Randomness of it simply because maybe you need to be turning quite tight or a certain speed for the system to notice it.

ABS pump seems to be whirring...though not entirely sure exactly how it's supposed to sound.

Car has to go back in anyway for tie rods....couldn't get it aligned because of play. Will see what new codes have been thrown.

I give up. Throw parts at it if you wish. I did and I still have the new K-40 on my shelf. It made no difference.

If codes can pinpoint the problem then I will solve the problem. But I'm suspecting they may not. $78 it's not a bad expenditure for a K 40 that I will be happy to have for other reasons.

Have you looked at the thread I started on 12-20-2009 with the title ABS, BAS, ESP lights on ?

Your problem sounds similar to what I had back then. It has been almost 7 years since I fixed my car and it is still working fine today. My fix involved replacing the K40 relay and another smaller one.