ASR light / limp home / fault code 6 - Page 3 - PeachParts Mercedes-Benz Forum

EricSilver · #31 09-06-2008, 10:47 PM

Quote:

Originally Posted by Arthur Dalton

Some Techs claim that even a 1/4" D difference can cause ASR code problems... which is why equal AP is so important...it is the rolling circumference that is the factor to be concerned with for proper WSS inputs..and AP has a direct relation to R/Circ.....
Worth checking into........

I definitely will.

Also, I replaced the front brake pads myself about 4 days before the inspection, and did use brake parts cleaner. Although it's possible I inadvertently cleaned a speed sensor, I will focus more on tire diameter.

EricSilver · #32 09-29-2008, 12:05 PM

Quote:

Originally Posted by JimF

Now start the car . . don't take your eyes off the IC; if the lamps dim . . .you've got a battery problem . . . and that will cause phantom problems. You should see almost no decrease in lamp brightness if the battey is "ok".

I misread your post. I just turned the key and looked at the lights without starting.

When starting, my lights definitely dim.

EricSilver · #33 09-29-2008, 12:08 PM

For me, this is distilling down into a voltage issue. Whether it is an Over or Under voltage is unclear, but arrows point to the voltage regulator and/or battery.

My car was parked for 2.5 days this weekend; conditions were very humid with heavy rain on Sunday. Sunday night I correctly assumed the ASR issue would return, so I drove the car and made these observations:

ASR fault appears to be triggered by a change in voltage, whether from A.) An electrical load being applied, i.e. the brake lights; or B.) A diminution of voltage/current from the alternator, i.e. foot off the accelerator, and engine/alternator revs dropping below an approx 550rpm threshold, and concurrent drop in voltage/current.

ASR illumination is accompanied by the click/ping of a relay (OVP?), audible in the center dash blower area (but on one occasion it sounded like it was coming from behind me).

The fault took MUCH longer to clear this time and I initially thought, “It finally failed for good.” But then the Common Sense Fairy pointed out, “This is your first drive in over 2 days, it is the first time you are expereincing it at night so your head & tail lights are on, you have the blower motor running, and are drawing a large electrical load – not optimal conditions for trickle charging a battery -- assuming low battery voltage is the cause.”

When the condition finally cleared, after about 30 minutes of driving (compared to the typical 1-5 min), I felt the urge to hear some music and turned on the CD player. Approaching a red light, I applied the brakes, adding electric load, and click/ping went the relay and on came the ASR. Turned off radio, drove a bit further, restarted, and the fault cleared as usual.

Evidence suggests weak battery and/or worn voltage regulator. I don’t know how the stop light switch circuitry works, beyond illuminating the stoplights, so I won’t rule it out as a cause either.

JimF · #34 09-29-2008, 12:26 PM

If the battery appears 'weak' (which the IC light test seems to confirmed), test it using a load tester.

But it does sound like you have a going-bad ETA. If you read my scenario (Menu#24) when mine started to go, the same events happened.

If your car "sits" for a few days, that shouldn't cause the ETA to be 'marginal' but the battery is further stressed esp since it appears to be weak.

EricSilver · #35 09-29-2008, 01:05 PM

Quote:

Originally Posted by JimF

If the battery appears 'weak' (which the IC light test seems to confirmed), test it using a load tester.

But it does sound like you have a going-bad ETA. If you read my scenario (Menu#24) when mine started to go, the same events happened.

If your car "sits" for a few days, that shouldn't cause the ETA to be 'marginal' but the battery is further stressed esp since it appears to be weak.

Jim, thanks.

I actually read and bookmarked your #24 as a "bible" when the problem first appeared last Fall.

The key variances with my car are that the ASR occurs only under (apparently) weak battery conditions, i.e., first start of the day if the car has been sitting for more than 24 hours -- or 15-18 hours if it is very humid, or very cold -- and goes away for good once the enginne has been running for a short while. Also, as you pointed out in post 11, the fault has not gotten worse over time.

In the IC test, I also notice the lights dim more in the mornings than they do in the afternoons, when leaving work. Also, and this may or may not be relevant to this issue, the SRS light remains illuminated a second or two after the other lights dim. Last night, it stayed lit for about 3 seconds and, if memory serves, this is also an indicator of voltage/battery issues.

I will have a load test done, and check the voltage regulator for excess wear. My current battery is at least 4+ years old, so I will plan on replacing it and/or the regulator.

dlafever · #36 10-16-2008, 03:02 PM

Eric,

Wondering how you solved your ASR issue. I just rewired mine last weekend because the harness was a bunch of crud. I had similar symptoms to yours but my ASR/Limp home eventually became permanent. I removed the ETA and under the non-control side cover found a mess of degraded wiring.

EricSilver · #37 10-16-2008, 03:36 PM

So far, I have done nothing, since there have been no issues.

However, what I wrote previously about voltage issues is only circumstantial. I now am convinced that my problem is related to the stop light switch.

After my last post, I did some experimenting. The issue has nothing to do with low voltage because, upon starting the car after sitting over another weekend, I turned on all lights, radio, etc. Nothing happened. If it were a voltage issue, as I originally conjectured, then the ASR would have tripped.

As long as I did not touch the brake pedal, the ASR fault was not triggered. If I idled the car for 1 to 10 minutes after startup (depending on temperature and humidity) I could drive away with no ASR issues. If I tapped the brake at any point before then, the ASR fault would appear shortly or immediately thereafter.

Not sure how it works, but the Stop Light Switch is involved in several functions, i.e. cruise control, ABS, ASR, etc., in which the ETA is also involved. So the likelihood of miscommunication is great.

On two or three occasions, on the first drive of the day, I have also heard a short, low buzz when applying the brake, very similar, if not the same, as the buzz you hear when you leave the key in the ignition – or when you blow the fuse that controls the instrument cluster gauges. I have never read any documentation on this, but that buzz might be a faulty stop light switch warning.

We have cold weather returning tomorrow, and I will observe the behavior once more, before going ahead and ordering the replacement switch (as I should have done months ago).

EricSilver · #38 10-21-2008, 02:06 PM

Following up on my previous post, behavior after idle continues as described. I am now also suspecting the coolant temperature sensor has a role is this.

It is the one component whose behavior/ non-behavior would consistently correlate to the temperature/humidity issues I have described throughout this thread. And I have noticed previously, and again in our current cold weather, that the ASR fault does not self-correct until coolant temp reaches 81/82. I will go out on a limb and say there must be a connection.

JimF · #39 10-21-2008, 05:32 PM

Measure the resistance . . about 300 ohms @ 100C. The failure mode is "increasing" resistance. So if it's 800 ohms, replace it.

EricSilver · #40 10-23-2008, 01:53 PM

Quote:

Originally Posted by JimF

Measure the resistance . . about 300 ohms @ 100C. The failure mode is "increasing" resistance. So if it's 800 ohms, replace it.

Brilliant, will do.

In late August/Early September I had to replace my expansion tank cap and coolant level sensor at the same time because of deteriorated o-rings. If the ECT(?) sensor also has a similar rubber seal, I am certain it too has failed, and is the source of the problem. Will know for sure when I am under the hood this weekend.

EricSilver · #41 07-23-2009, 12:58 PM

Revisiting this issue:

While under the hood today I noticed powdery-white corrosion on the bolt-down plate that secures the battery, and some additional corrosion on the positive terminal. I removed battery, cleaned/scoured away all visible corrosion, and replaced it.

Upon starting the car it fired up very strongly and the tach, instead of surging a bit as it typically has been doing, remained locked in the 1000 rpm range. Upon driving off, the anticipated "first start of the day" ASR fault did not occur.

It’s too premature to say for sure the ASR problem was a voltage issue all along, but I’ll chime in again after a week or so if it does not return. Nonetheless, it probably is/was electrical, with the NSS playing a role.

7/27 Update:
Still no ASR faults.

emerydc8 · #42 12-18-2011, 02:50 PM

Quote:

It’s too premature to say for sure the ASR problem was a voltage issue all along, but I’ll chime in again after a week or so if it does not return. Nonetheless, it probably is/was electrical, with the NSS playing a role.

I'm curious, do you think it was a voltage issue that was causing the problem? Has it returned since?