560SEL intermittent ABS and SRS Lights - PeachParts Mercedes-Benz Forum

tinypanzer · #1 05-20-2010, 07:18 PM

Hello all,

Recently, while driving, I have noticed that the SRS light will come on for a few seconds and then extinguish. Same with the ABS light, but neither come on at the same time (yet).

There is no performance change or stalling, or the normal OVP relay symptoms.

Could this be OVP related, or should I look elsewhere first?

Thanks!

mbdoc · #2 05-21-2010, 09:10 AM

Since those systems share nothing in common except their need for power, I doubt they are related.

Could be a charging system issue.

mlozzi200478 · #3 05-22-2010, 03:17 AM

check the output of your alternator,then check all battery terminal ends for tightness,sounds like low voltage causing the lights to come on,if you have the old style battery make sure the water level is topped off.

tinypanzer · #4 05-24-2010, 06:53 PM

Thanks for the suggestions, folks.

The battery is almost new, as is the voltage regulator. Nothing else appears to be starving for power, accessories and windows and lights all seem happy with the system voltage. I'll start poking around.........

On Saturday, the ABS light came on and stayed on for several minutes on a long drive. Haven't seen it since.......

This is the problem with having electronics in all your systems but not having any diagnostic code memory. Ugh.

I have a complete set of ABS relays that I snagged and Pick N' Pull, I might try to swap those out for a test. It's probably a cruddy sensor or connection, though.

The SRS system is a whole other can of worms.

After I get done verifying proper voltages, where is a good place to look next?

Thanks!

mlozzi200478 · #5 05-25-2010, 12:30 AM

well,you may want to clean up the sensors, they get dirty. sometimes fill up with water,check the abs pickup on the back of the rotors or hubs,make sure the slots are clean it kinda looks like a gear with unbeveled teeth.replace the abs relay and sensors,that should do the trick if cleaning hasnt solved the issue.

mbdoc · #6 05-25-2010, 09:05 AM

IF & When a wheel speed sensor caused the ABS lamp to come on...The light will NOT go back off until the key is cycled.

IN other words, the light won't go on/off while driving.

Power supply is the only reason for the ABS lamp to cycle while driving!

Overcharging can be the culprit as well.

tinypanzer · #7 05-25-2010, 02:28 PM

Thanks, Doc. You just saved me quite a bit of troubleshooting. I will rig up a DMM with hi/lo memory and put a cigarette lighter plug on it so I can monitor voltage in real-time.

So strange, it hasn't happened now in three days.......

tinypanzer · #8 06-03-2010, 06:21 PM

Hello all....

Update - I have replaced the OVP relay with one that I had on my shelf as well as re-terminate the two smaller red wires that go to the positive terminal of the battery. So far the problem has not happened again....... So it's looking like either the OVP had a problem, or the cruddy connection at the battery was to blame. I guess only time will tell if it is truly fixed. I think I may crack open that old OVP to see if there are any bad solder joints in there. Although, MBDOC says that the OVP shouldn't be able to cause this condition and I believe him. Strange..........

tinypanzer · #9 06-10-2010, 05:01 PM

Well, the ABS light has quit coming on, but the SRS light continues to come on for 2-3 seconds then go out, usually only once per trip, and it seems as if it happens on the same stretch of road every time.

Bizarre...... Anyone have any ideas?

BENZSTER · #10 06-11-2010, 03:21 AM

There is a contact ring for the SRS system under the steering wheel. I would try cleaning this first before replacing any parts.

mbdoc · #11 06-11-2010, 09:43 AM

I only suggested that the source of power for the ABS & SRS come from different places.

You have also figured that out. Glad the ABS issue is fixed.

Now back to the SRS. Most likely issue is still power supply. Otherwise the lamp would not go out w/o erasing codes.

Using that DDM on min/max record while driving is the 1st step to correct diagnosis.

tinypanzer · #12 06-11-2010, 07:18 PM

Thanks, DOC. I'll do that ASAP and post my results back. Oddly, last night it happened three times and I was going on the interstate at around 90mph (empty road) and absolutely no other symptom other than the light. I will go fab a meter to lighter socket adapter now......

tbomachines · #13 06-11-2010, 08:47 PM

Funny my 300E just started having the SRS light come on randomly for 1-2 seconds or so. I'm keeping my eyes on this thread...At least for mine I doubt it is the contact rings, that would likely be consistent whenever the wheel turns full lock or strikes the point. Another potential cause for the SRS light coming on intermittently would be seatbelt sensors, but that would retain the code if I read this right. Please keep updating, I will be reading!

tinypanzer · #14 07-19-2010, 07:39 PM

Okay, it took me a while but I finally cobbled together a lighter socket to DMM adapter, and I've been running with it for a week now. It took a while for the SRS light to come on during driving, but it finally did. When I checked my meter during this event, the voltage was 13.34, which is fine. The high was about 13.46 and the low was 13.2. This seems like my charging is completely normal.

If MBDOC is right about the voltage being off during these events, it must be isolated to the SRS unit.

Can you think of another test point to monitor the voltage to just the SRS unit?

Thanks!