The ETS (Electronic Traction support)
and ABS (Anti-lock Brake system) warnings light come on
on my 1997 E-320 (150000 miles) everytime I start it. It first started
while braking downhill on a rainy day. Any suggestions on what I
should look for. Thanks

Should I scan for codes and clear?
Top off/replace brake fluid?
Check/Replace pads?
Should I look in alldatadiy?
Put back missing brake pad sensors? They were installed without the sensors by a novice tech.

My last oil change was 8000 miles ago.

 

More symptoms ...

the "Check brake light" warning has been on for several monthsprior to the ETS/ABS warnings
coming on. The rear lights on the trunk (left and right) work ok when brake
is depressed. The brake light on top of the rear seat middle does not work 99% of the time
when brake is depressed (bulb is verified ok). Once in a while the brake light on top of
the rear seat does light up faintly.

Could it be a faulty brake switch? If so any one have any pointers to replace?

Thanks

 

Unlikely there is a direct linkage between your symptoms and ETS/ABS problems but it appears that your car is in need of a little TLC.

Start with the Brake check light first. This is on for a reason!
Is the brake fluid level correct or below sensor? If low top up to correct level. Low level is indicative of worn pads/rotors or a leak.
If pad wear warning sensors were not fitted this will cause the Check Brake warning to illuminate unless a dummy connection is made to simulate the sensor. The sensors are a great idea but if correctly replaced with a dummy will cause no problem OTHER THAN you will not be advised when your pads next require replacement. Why not replace these sensors. All they are is a bit of looped wired encased in plastic to fit the hole in the pad! OK they cost a few dollars.

The High Centre Stop Light uses the same power source as the other rear Stop lamps. If they work OK there must be a fault in either the harness breakout connection, the downstream wiring or the High Centre Stop Light unit/LED's or bulb.

Getting the DTC codes read is really the next thing you need to do but this will cost you and may require that you go to an MB dealer. Reading body codes is different to engine codes. You need much more sophisticated equipment. ETS/ABS codes usually self set once the fault is removed.

The key pointers I observe in your post are.

Annoyance symptoms left unresolved. Non main dealer maintenance. Iffy maintenance practice..non replacement of wear sensors.
ABS AND ETS BOTH out. Common components. Most likely wheel speed sensors.
Wet at point of failure.
Wheels & Brake pads have been removed recently

I SUSPECT that you have a bad connection on one of the 3 or 4 wheel speed sensors. Check the condition of these connections which pass into the rear of the hubs (or sometimes the diff casing) to ensure a good corrosion free connection. If you are DIYer a comparative resistance check on the sensors (disconnected) is a good elimination procedure also. Is the wiring between the connection and the sensor in good order/undamaged?

Suggest you eliminate these opportunities and see where it takes us.

Stuart

 

My wife's 97 E300D displayed those fault codes and the radio turned off and on by itself at idle. My voltage was jumping around wildly, especially at idle. You can monitor your car's voltage by holding down the REST button on your climate control until the AC diagnostic mode displays. Toggle through the options with the temp until you get to the voltage (I think it is 24) it will display the continuous voltage 12.9, 13.1, etc. Mine was very erratic, dropping as low as 10.

What solved my problem was removing the negative battery cable from the body. The connection was pitted, corroded and had clearly been arcing. I cleaned it up with a file and some sandpaper andIadded a washer so it would get a good tight connection. Problem has been solved ever since. It's been about a week and a half, including a 540 mile road trip yesterday.

BTW, 29.98 MPG with B50 biodiesel this trip.

 

Agreed. MB's of this vintage are very susceptible to voltage fluctuations.
Need to ensure that the system voltage is OK = 12.5 min (idle on load) to 14.5 at 2000 revs +.

Stuart.

 

Thanks snanceci and DieselTwins for the suggestions.

I finally got around to working on this. I fixed the problem by replacing the brake switch. Part cost $25 from the dealer.

The hard part was getting access to the switch.
I found the switch under the instrument panel just above the brake pedal. After
I unscrewed the panel above the brake pedal, I found I had to remove two
things: the OBD port and trunk release switch. The OBD port is clever design.
To remove the OBD port you have slide out to your right the port housing and
the wire come out cleanly. The trunk release switch is screwed (one screw) to the
panel. Removing this screw and twisting trunk release switch allows it to come free.
With these two out of the way, the panel can be completely removed giving
free access to the brake switch.

Replacing the brake switch itself is easy and there are a couple of posts on the
MB forums that detail this.

Thanks again to everyone for their suggestions.

 

Snaceki, small correction. The ABS and ETS warnings have gone away.
However, the center brake light problem still persists. I will follow your
suggestions in your earlier post and will post follow up. Your help is
appreciated.

 

Hi,
I was going to ask how some of the brake lights worked and the centre High Stop light didn't when they are driven by the same switch.

My concern now resolved!

The switch has two circuits. One Normally Open. One normally closed. It is quite common for one circuit to go bad.

Stuart.