nopcbs

I have a 2006 E320 CDI with 35,000 miles. I mostly drive it in winter and it just came out of summer storage. Last winter it was running fine, although I did occasionally get a weak battery message that resulted in "convenience" features being disabled until I had driven a few miles and the weak battery was charged up.


Well, just started driving it again and the weak battery/convenience features disabled message is back big time. Along with that I have the glo plug symbol in the dash light up and stay lit while driving. The car drives fine...other than no bun warmers, rear defrost, heater fan motor which are all convenience features. I get the red "go to workshop" warning with a picture of a battery above the message and the service required icon on the dash.


The car was still on original batteries, so I put in new main (in the trunk) and aux (under the hood) batteries. Both test excellent with a Solar load tester (over 1000 cca for the main Deka battery, which is spec'd at 850 cca and 230 cca for the YUSA aux battery, which is spec'd at 200 cca).


Well, that did not improve anything. Still get the same weak battery warnings and the red "go to workshop" with the battery picture, the same glo plug icon lit on the dash, and the same service required dash message...and no "convenience features. Car, otherwise, still runs fine. Neither battery seems to drain much in my 13 mile round trip commute (if I put a battery tender on either when I get home, it does little or no charging).


I put on an OBD2 code reader and there are two instances of code P0683 "Glo plug control module to PCM communication circuit". A little Googling seems to indicate this is caused by a bad pre-glo relay.


OK...maybe the relay is gone and that would explain the glo plug icon staying lit on the dash, but what about all the, seemingly, battery-related symptoms...even with brand new batteries.


I would think that if there was an alternator or battery relay problem, the OBD2 would indicate that.


This is all very frustrating and puzzling. (It also makes me wonder why I bought a Merc instead of another Lexus...oh, yeah...I wanted to try a diesel car to save money on fuel. That worked out real well too, with gas under $3 a gallon and diesel over $4.)


Anyone have any thoughts on what the heck is going on? I have an appointment with a local import specialist next week. He supposedly just had another customer with a similar problem. Hope he fixed it.


- Geo

Plutoe

"I would think that if there was an alternator or battery relay problem, the OBD2 would indicate that."--------That is your problem the OBD is emission related faults only and glow issues are emission related, however the battery control module is not and that is where I would start---start that is if you have the proper MB diagnostic equipment---if not you are left with the iladvice from the Abu Massa/local import guys!! who typically have great donuts!!

BagMan

Did you check the voltage that the alternator is putting out? It should be around 14v at idle.

My guess is it's the alternator or voltage regulator

nopcbs

After standing overnight with no battery charger or tender used, the (new) main battery reads 13.4 v and tests at 1015 cca. (The now disconnected 8-year old old main battery still reads 13.1 volts, by comparison.)


After standing overnight with no battery charger or tender used, the (new) aux. battery reads 12.8 v and tests at 230 cca.


Both cca figures are above the batteries minimum specs of 850 cca and 200 cca, respectively.


With the engine on and measures at the battery terminals, the main battery voltage is 14.1 v and the aux. battery voltage is 12.8 v.


It appears that the aux. battery is not getting charging voltage. However, at 12.8 v it really does not need it and it is not being drawn from, anyway, in normal running (right?). It's just for brakes backup if there is a failure. It may also be that MB designed their system so that the main battery gets charged before the aux. does, in normal running.


Also, I reset the fault code for that glo plug communication error code...and it came right back after I turned on the engine. I suspect I have two things going on.


I found another post that suggests I may be having a voltage regulator problem. That person claims MB alternators are robust and rarely fail (remember, I am at 36,000 miles), but that the voltage regulators are "wear" items. That would betray poor design by MB, but who knows.


- nopcbs

rediesel

35000 miles is too few for an 8 year old car - especially a MB diesel

I'm thinking it's battery control module, but that's an uneducated guess. Take it somewhere with a Star-diagnostic or equivalent software system.

Have you read this?
https://mbworld.org/forums/e-class-w...-workshop.html

nopcbs

I bought it when it was about 2 years old and had 18,000 miles. I just drive it to work winters (have good snow tires on it and excellent undercoating) and put about 4,000 miles a year on it. In summer it sits under a cover on a battery tender.


Yeah, I know, not efficient use of a diesel...especially since diesel jumps in price like crazy in winter in my state of Michigan.


Thinking about trading it on an X3 or X5 3.5i.


- geo

nopcbs

Tuesday of Thanksgiving week, I had an appointment to take the car in to a local (and very good) import service shop, Rallye Automotive in Midland, MI. Well, I fire up the engine and...the car runs completely normally. No red go to workshop, no glo-plug light, no convenience features disabled messages. Just the leftover "check engine" light still lit. I read the code (P0683, glo plug control module communication circuit), reset it and drive the car for about an hour. No problems. I call Rallye and talk with the owner. We decide that maybe it was a fluke or a bad contact or even some moisture on a contact that finally evaporated due to engine heat (car was stored all summer) and no error code means nothing to read on a Star diagnostic computer. We decide to wait and see what happens. Later that day I get the glo plug and convenience features disabled message, but they go away pretty quickly. The next few days I did not drive much, and the error states (glo plug light and convenience features disabled) came back and went away a few times. The check engine light came back on and I checked the codes: P0683 (as before) and a new one P0671 (cyl 1 glo plug circuit open). Both codes are coming up regularly now.


Todays drive home was very strange. Car started normally (always does), then I got the red go to workshop and the glo plug light and the convenience features disabled. There are two states the car goes into when it thinks you have a weak battery. In one things like the heated seats and rear defogger are disabled. In the second these plus the heater blower motor are disabled. As I drove home (7 miles) the heater blower motor started cycling one and off indicating the two states were being cycled between. The seat heaters stayed off.


Got home and dis some diagnostics:


Had both error cods, P0683 and P0671.


Load tested main battery and it came in at 950 cca (spec is 850). This is less than the >1,000 cca it had been giving.


Main battery engine-off voltage was 12.4v. Engine-on main battery voltage is 14.2 v (with no error messages showing on dash), not sure what it is with error messages on.


Put the main battery on a maintainer and it did not immediately go into a "charged" light on state. Put the battery on a regular charger and it charged at ~20 amp for a minute and then the fully-charged light came on. Put the main battery back on the maintainer for over-night. (It's fairly cold here, ~30F.)


I am perplexed. I don't mind taking the car in to Rallye (or even a Merc shop), but the symptoms are just crazy. I buy that the glo plug codes may be a bad glo plug or a bad glo plug controller, but the off/on battery charge faults make little sense.


Heck, maybe the glo plug codes are just an artifact of a bad voltage regulator on the alternator screwing up other sensors.


Remember, this thing has only 35,000 miles on it, too.


More and more I think Germans should not be allowed to try to design electrical components. They are just no good at it. MB should hire some ex-Toyota guys for that and do the mechanical parts themselves.


- GRL

mersum1es

Sound charging problem (or maybe grounding problem) to me. You can put voltage reading in your instrument cluster via 'service menu', and see if it's dropping when error messages appear. Reading is not as accurate than measuring from battery poles but gives some guidance.
Battery control module has been suspected often, but rarely it is the culprit. However there is software update for BCM, which indy or dealer can do via SDS. Also BCM itself has hardware update. Some insight about BCM function in WIS document GF54.10-P-1001T (found easily by google)...

About aux battery; it's isolated from the system all the time expect when it needs charging (controlled by BCM).

nopcbs

Thanks for the useful information. I have tried to use the in-dash voltage display, but the car cycles so quickly in/out of the "convenience features disabled" state that I have not managed to do it, yet. I suspect that you are right about a charging system problem being the cause and I fear it is either a continuity fault or the (pricey) BCM. The former may be tough to locate and the latter is...expensive.


I'll call a dealer to see if my car is due for the ROM update or not. It is the last year of the pre-facelift W211, so maybe it already has it.


Thanks, again.


- GRL

nopcbs

The problem is solved at the cost of $1137 for a remanufactured alternator/installation. That's at under 37,000 miles, by the way. I took the car to Rallye Imports, a local import shop, and they put it on their OBD2 reader. It came up with three pages of error codes centering on the alternator putting out an unstable wave form that screwed up the logic circuits in the sensors and generate all those battery problem messages. It was also the cause of the glo plug communication error code. The only remaining code is an intermittent glo plug continuity one on cylinder 1. It only comes up on the first start of the day.


I am more than a little hacked off at MB and Bosch for being unable to build a reliable alternator. This thing failed at great cost in under 37,000 miles. A term beginning with "c" and ending with "p" comes to mind. I've NEVER had an alternator fail in any of the other cars I've owned out to well beyond 100,000 miles and 20 years of ownership.


- nopcbs

rkucemba

I've been having a similar issue with my car, same as yours, 2006 e320 cdi. I replaced the aux battery and all the convenient functions worked for two days, replaced alternator and no difference. It's getting hot and I have no fan. Can anyone help?
Robert

mersum1es

Convenience functions are handled by main battery, aux battery should not cause message (only if aux is bad and requires charging from main battery al the time).

It may be simple current leak which draws your main battery empty, worth to measure.

What are main battery voltage levels before start after drive, when disabled functions appears (only after start or later too). All connections tight, alternator voltage regulator right type?

rkucemba

I'll check the voltages, the convenience functions turn on for a second when I start the car.

Rossafuss

Having the same exact problem as OP. Same codes and everything.
only issue is, the alternator is only 6 months old, and the glow plug controller is only a year and a half old.
My alternator and regulator however IS aftermarket. Is it possible that the aftermarket regulator (which has been working flawlessly for 6 months) is causing communication issues?
As OP stated, his alternator was apparently the cause of the issue.

Robert Kucemba

Rossafuss

So you had the same issues as OP? Mysterious glow plug light and everything?

kajtek1

Inspect, inspect, inspect.
Assuming that alternator replaced year ago has to be good doesn't always work in real life, especially in last years when MB shifts parts manufacturing all over the World.
W211 has very convenient voltage display on the cluster, so why instead of scratching your head, drive with the option on and observe what changes when the messages appear.
I would imagine that Glow Plug light might be separate issue, but fact is that those care have so many electronics, that anything is possible.
I will remember forever, when W211 with SBC was displaying convenience off message for whole week on my vacations. It was coming on and off at will, when voltage was shown to be steady around 14V.
Only after returning home I took magnify glass and found battery clamp not torqued properly.
The engine never hesitated to start, but seems oversensitive electronics were sensing clamp resistance and popping up errors.

Rossafuss

Here's the full post I made on the issue, including all the diagnostics I've already done.
https://www.benzworld.org/#/topics/2995221

I was just following up here to see if OP actually did fix this, since we have exactily the same issue.

boogsenior

check the battery control module in the trunk--located near the battery a couple of inches from the trunk latch Looks to be about the size of a pack of cigarettes. The small wire connection has about four or five small wires in a connector, that connector might be loose just make sure that it is plugged all the way in. That was all that was wrong with my system. Just about drove me crazy. Let me know if this works. Thanks