MB-Dude

My '96 SL600 can't pass California smog inspection, because the OBDII is reporting a number of "Not Ready" situations. Car runs good and pass the emission tests with flying colors; very clean emissions. But because the OBDII has "Not Ready" indicators, this technicality is cause for not passing the smog inspection. Also, the infamous "Check Engine" MIL is not lit. No trouble codes are present and the dealership is scratching their collective... well, heads. I suspect during their testing (or the previous owner), some codes may have been erased.

Removing battery power for 30 minutes had no effect... except causing me to have to reset windows, radio, etc. - normal stuff. But the ECU's, even after a full drive cycle say "Not Ready". The "Brainbox" where the ECU's are mounted is clean and dry. Also, the ridiculously puny cooling fan for this box appears to be working.

Considering there are no Trouble Codes and the "Check Engine" light is out, I'm beginning to think there is one or more computer registers latched in the ECU's. Thus, if there is some way to reset the boxes back to factory-fresh (except for VIN information), this might either clear the problem (after a drive cycle) or at least cause a series of Trouble Codes to be generated.

Question: Does anyone know how to completely reset the ECU's, except for the VIN?

Moviela

Did you try CRTL-ALT-DEL? Just kidding, but seriously there is a 8 yr/80,000 federal emmission warranty. You might qualify depending on the in service date, and when you failed the smog test.

rocknty

Can't get the sensors to come up on my '96 E320 and the CA ODBII won't pass the car. Sensors where checked by dealer and they say they are working?

Dealer says to replace ECU for $1400. This is frustrating and expensive.

Is there a software upgrade or something else someone knows about that can be done?

HELP!

Thanks,

Ty

Tishers

Does this shed light on the problem?

http://www.tmo.com/theory/myth/ecureset.htm

rocknty

No, I am wondering why these sensors wouldn't reset even after 2500 miles of driving.

Wondering if there is some kind of defect with first generation W210 ECU that can be fixed with software update or a code.

Ty

MB AMG

Hmmm, I have a similar problem!

benzmodz

The Siemens head unit on S, SL, CL are running the windows operating system .... not so far from the truth after all.

MB-Dude

First, thanks to all for the posts and suggestions thus far. I especially got a chuckle from the CTL-ALT-DEL response... but couldn't find the DEL key! Seriously, the car is still not resetting the sensors through the OBDII. Dealer is useless, but have a couple of shops taking on the challenge. Concern now is how the heck do I get my registration completed! Paid the California fees, but they will not issue a renewal without a passing smog check. So I'm currently drinking heavily, hoping the blurred vision will give me insight!
Cheers!

Kanji

is the place you're getting the smog, a discount smog? i just found out that certain smoging test place have different qualifications. meaning, some of the people who say's that they can smog u're vehicle for cheap usually got their qualification by phone or garage. A situtaion happend when i when to smog my 98' VW 1.8t passat at one these cheap smog station. i have upgraded some parts for performance and passed smog year after year. I one day decided to try it at one of the cheap deals and basically failed smog. So i took it to a dealer to have it checked out and see what happened or how can i get it back to passing smog..dealer say's there's nothing wrong with the car. I too had the OBDII sensor stating that it can't talk to the smog computer or communication error! Found out certain garage has different software in their computers to smog vehicles. find a reputable smog station usually reffered by deputies or police officers and do it right with less expense.

MB-Dude

First, thanks Kanji for the information. However, the lack of ECU communication has been replicated at different shops; including the dealer.

Good news, though -- Today we may have made a breakthrough. Seems one of the Engine Control Modules has a fault. The fault is repeatable, though the testers code needs to be deciphered. It’s looking more and more as if I will have to replace at least one of the ECU’s. OUCH!

Two questions for the forum…
1. If I have to replace one ECU, should I replace them both?
2. 2. Anyone know of a place other than the dealer to buy ECU’s?

Could be a 2x OUCH! Considering the cost of these babies through the dealer. More to come, my friends.

mleskovar

...the ECU is not faulty, but just needs to be reprogrammed? Aren't they EPROMS?

Moviela

Hey MB Dude,

I am not well informed about 96 model cars, but I do know that the ECU for my car cannot be replaced by the same ECU from another car because MB uses a software key that is unique to each car. I do know about these fellas in the UK that fix a lot of ECU's. You might contact them.

http://www.bba-reman.com/

MB-Dude

Good idea about the EPROM's and reprogramming. However, because the car runs good and does not fail the emissions specification, the main engine control EPROM programming is probably OK. Remember, the ECU(s) simply do not "register" the readiness of certain sensors, which we know are OK.

In fact, today's work on the car indicates the problem may be some components within the ECU that have to do with communicating with all the various stuff and sensors. A couple weeks ago, I opened both ECU's, looking for anything obvious. Nothing looked out of the ordinary, but I can tell you that the ECU's are A) made up of 2 PC Boards in each ECU and B) they are both packed with surface-mount digital chips. There ain't much air in those boxes! Very complicated… and I work in the semiconductor industry.

I think the problem is not the EPROM's but one or more of the secondary communication chips within the ECU. We're researching deep fault codes as of this writing. What I do know about ECU reprogramming is that the power table gets reflashed. The table that is programmed by Mercedes is fairly generic and covers many circumstances. Thus, if you run a particular grade gas, under particular conditions, a more specialized table can be created and programmed in. This is what the PowerChip guys do.

The other suggestion, about a software key, is partially correct - each ECU from Mercedes must be coded with the VIN of the destination vehicle. From what I have been told, it is partially for theft prevention; partially to prevent fraud during US smog inspections - the Smog Technician must ensure the VIN in the ECU matches the car's VIN. I do know of a circumstance where ECU's from one car (not mine) were used temporarily in another. The car ran like crap until it "taught" itself the new engine parameters, but it worked – at least long enough for testing purposes.

Moviela

I/O can be a problem in any system. It is most exposed to the "outside world." Did you have a chance when the boxes were open to inspect under a microscope? Could it be that you have a simple soldering problem that can be solved at a decent rework station?

I have found execution of surface mount assemblies by Europeans to be less than ideal. Does Mercedes have a wiggle mode like Ford does to help trace problems in the wiring harness? In the Fords you enable the mode, then wiggle the connections. If a problem occurs with any sensor, a buzzer on the code scanner sounds off.

There was a limit on how much you had to spend before you got a wavier, around $ 300 or so. Is that limit gone now?

Hope you get it fixed before they jack up your trousers and rotate your wallet!

MB-Dude

I didn't inspect the solder traces under a microscope, but I looked at both PC Boards, in each ECU, very carefully. It is possible that there's a bad trace, and perhaps someone here in Silicon Valley could fix it... once the fault is found and defined.

As for costs to date, they have been minimal. The independent shop I use is very fair and unless they make progress, they don't charge. Even though the car has been in the current shop for about 10 days, they have made minimal progress. I am mentally prepared to replace both (if needed) ECU's (at $1,500 each; deeply discounted), but want to get some proof and assurance that they are bad and that replacing them will solve the problem. Trouble is, there is no “test” for determining if an ECU is bad – you can only eliminate all other possibilities first… and there are WAY too many possibilities to check!

But, I will continue along for the time being trying to confirm what the problem is... it's "my car". And a '96 SL600 is somewhat of a rarity.

MB-Dude

OK, here's an update to the saga listed...

Got the car back from my independent mechanic. Car runs great; perhaps even a little better than when I dropped it off.

The independent MB wizard did the following...
1. Swapped ECU#1 & ECU#2 with each other (#1 goes to #2 and vice versa)
2. Using a diagnostic computer, he cleared all codes & registers
3. Re-coded the drive parameters

Step #2 above was rather intense as it immediately generated a TON of errors on the ECU's. But after thinking about it, that is exactly what we wanted... to make the ECU's "factory fresh". It is possible!

Once the ECU's were deeply and completely reset, the car needed to go through the entire Drive Cycle sequence. This is where I am currently -- driving the car to fulfill all the Drive Cycle requirements.

At last check yesterday, there are only 3 parameters that are left to toggle from "Not Ready" to "Ready". This is very encouraging as we had well over two dozen after the recoding. Also, the Left Bank O2 Sensors are now showing “Ready”. Prior to all this, neither bank was coming up “Ready”. I believe the Right Bank O2 Sensors were just lagging behind a bit.

I plan to continue driving the car this weekend and take it back early next week to see if these last three items come up “Ready”. More to come next week.

MB-Dude

The '96 SL600 continues to run well. In fact, I sense the car is a bit quicker now (after the recoding) when the engine is cold. I do not think this is directly caused by the recoding, but that the ECU's are now more "in tune" with all the sensors. (No pun intended.) Still working through the Drive Cycle sequence, though. If I can make the time from work, I'll take the car back to the independent and we'll see what the diagnostic computer says. Still more to come!

MB-Dude

Well, took the car back to the independent for (hopefully) the last check. But ALL the "Not Ready" codes came back!!!! Talk about being PO'd! Drove the car for the week - damn thing runs great... but the ECU codes are still "Not Ready".

This afternoon, I took the car to a different dealership; one that did a good job fixing a computer problem on a '88 420SEL. After a shirt discussion, these guys immediately decided to *research* the problem before I drop the car off next Tuesday. I found this encouraging -- that they wanted to review the technical aspects BEFORE leaping into the problem. Also encouraged by their lack of leaping to the must-be-a-bad-wiring-harness routine.

Well my friends... more to come next week as this saga continues. It's getting to be worse than the Star Wars installments!!!

rocknty

I am waiting to see what happens with your latest attempt.

My sensors won't come up and I am stuck with a potential $1300 new ECU bill.

What scares me is that it might not come up after that if there is an issue with the downstream communication units that talk to the actual sensors.

Meanwhile I am driving around with no registration sticker and looking in my rear view mirror for 'la policia'.

Ty

MB-Dude

Dropped the car off with a different dealer yesterday (Tuesday, 20 Sept). Got a call today that they are 100% positive that one and only one of the ECU’s needs replacing. Nothing else. As noted above, the dealer’s Service Technician did some research on Monday, so he was more or less prepared when I dropped it off on Tuesday. Now remember… this car can’t seem to hold generate a series of “Ready” codes under any condition. So it’s not like I have an intermittent problem. The fix will be REAL easy to verify!

I have authorized the replacement of the ECU for a number of reasons. First, all my previous work on this problem sort of indicated one of the ECU’s were bad. Remember, the problem seemed to move around when the ECU’s were swapped. (My V12 has a pair of ECU’s; one for each bank.) Second, the dealer told me they are 100% sure this is the problem. Third, they did NOT even ATTEMPT to sell me a second ECU, wiring harnesses, sensors, gaskets, electronic gizmos, stuff, doo-dads, etc. Only one part… a single replacement ECU.

But most importantly, the problem solution makes sense and I was mentally prepped to replace the ECU. It’s tough to prove the ECU is bad, but at least I have found a dealer that has the resources and troubleshooting skills to put their money where their mouth is. Well, at least so far.

More to come, as I have to wait for the ECU to arrive; hopefully this Friday. Will update as I get more info. In the meantime rocknty, watch for them blue lights!

mleskovar

Did they plug another/test ECU in to verify? Sounds like they did if they're so sure. Good news (everything's relative!). So how much $ do you save in the end?

agentMurdoc

wow that is a saga! It may not be the prefered solution, but my solution to the problem would have been to just bootleg smog it and be done with it. They are all over SoCal, cheaper than fixing it and faster too :p

Moviela

It is a shame that no one can repair these computers except the manufacturer. Do you get to keep the offending ECU or is it sold on an exchange basis? I visited a repair facility for ECU's, and they had a panel jockey test the unit on an automatic test machine, then swap the indicated circuit board. A tear down parts list shows about $50 for cost of components, 20 mins of labor. For this they want a grand? I hope this allows you to pass the smog test.

You are not the only one who is having trouble passing the smog test. Have you seen this?

https://www.mbwholesaleparts.com/Sta...edFSBMar05.pdf

benzmodz

There is a company in the UK that repairs the ECU.

http://www.electroniccarparts.com/

Please look into these things before stating that NO ONE does the repair.

Chappy

It may be too late for your situation, but here's a company that may have what you need.

http://www.beckmanntechnologies.com/products.html