Car is a 2009 SL550 w/ under 60k miles and sport package. I am considering purchasing from a friend. We went for a drive the other day and it has a couple of issues. He is willing to give me a good deal on it, I just need to decide if I want to deal with it. He's offering me the car for $18k and its condition is excellent, which is why I am considering it. I just don't want to end up with a problem that is going to cost me more than $3000-4000. I may just have to take it for a diagnostic, but I think that if I can't get an appointment tomorrow and decide by the weekend he might just go to trade it in.

He has been having top problems (I can't remember the specifics, but he said he can put the top down we just won't be able to get it back up or something like that). To me this seemed like a part issue with a cost to repair of around $1000, but maybe he and I are both clueless. I will call him tomorrow and ask him what the problem is specifically.

The thing that concerned me more is related to the electrical system. Apparently he thought the battery had gone bad (probably for good reason), and replaced both front and rear batteries. When we went to drive the car, the key also did not unlock the doors with the remote button, even though the battery is new. Then I tried to push the start button on the shifter and it did not work. However I turned it on with the key and then turned the car back off, at which point the start button did work. We went for a drive, stopped by the convenience store. When I got back in, I got a reduced brake effect message in all red when I went to turn the car on. I turned it on and it cranked fine. Turned the car off, and the message was gone the next time I started it.

I have read that these both could be battery related issues, but given that the batteries are new, is there something I'm missing? Maybe that the battery hasn't been calibrated if that is a thing? My first thought was that if there are electrical problems with a new battery, then it would be the alternator. My understanding is that the issue could be voltage related as the braking system checks the voltage and issues a warning. The fact that the car has problems locking and unlocking on its own / the start button doesn't initially work causes me to think it's electrical. But if it were the alternator, wouldn't that mean it wouldn't be able to build a charge while driving it? The car does not warn that I may not have convenience features. I also considered that if there is a faulty piece in the hardtop system that it could be stuck drawing from the battery, and the car could be charging via the alternator.

I've searched the forums a bit and I haven't read enough to know (but enough to simply suspect) that it could be SBC related. If that is the case, would I be covered under the warranty if I am not the original owner or the person who has been servicing the car? I don't have a multimeter so I can't check. Any advice would be appreciated.

 

Let me put it this way. If you were to take it to the dealer with locks and top not working and an elusive electrical issue, you will probably have a bill between $5k and $10k and over $10k would not shock anyone on this forum. It is also probable that a knowledgeable DIY could fix it for a few hundred dollars, but if that isn't you, I would stay away from it.

 

Thanks, I'm no stranger to troubleshooting, but I thought someone here may have had a similar experience. If this is something exemplary of something like, let's say a car getting rained in vs. typical part failure, then I'd stay away from it. If these seem to be common things that just need fuses, a failing sbc, etc. then I might as well pick it up and troubleshoot it. At first I thought it was a battery calibration issue since the batteries are new, but I didn't find any battery calibration information after a quick search. If it's probable to be able to sort it out for under $2000 on my own or with minimal help from a good indy shop, I might as well get it. There's a very honest one nearby that has factory techs for $170 an hour. I don't do dealers except for TSBs and recalls, but I am big on OEM parts.

I'll also have to drive it 100 miles straight after picking it up which is a concern. Seems from searching that the top opening but not closing is a bit of a common thing? Talked to a couple of techs about it this morning and it seems like it'll either be a switch or the cylinders. Apparently the center one typically fails first, then the ones on the sides of the trunks after. He said pull the liner and check for leaking. So I suppose those are the next steps. Hopefully I can get that done before he trades it in.

 

My only concern with driving it, and not a minor one, is that you may have an issue with the brake power supply. Unlike most cars where loss of brake boost just means a little more pedal effort, these cars lose almost all braking. Now, the warning light can be caused by a lot of things and MIGHT not indicate that you are about to lose braking, but I'm not sure that is a chance you want to take.

 

The battery control module alone is $2000 used. These cars aren’t ever fixed, just waiting for the next repair to happen. I would only own one if I could do all of the repairs myself. $3000 to $4000 is nothing to spend to repair these cars.

 

Sometimes, low voltage sets off the warning, but it could also mean the SBC unit has a problem. Since the SBC pump runs on electricity, a bad battery or alternator could lower braking power.

 

I talked to him today and he says the issue is the trunk actuator. $700 to repair it. Does this make sense given the issues with the central locking? My impression is that if the trunk isn't closing properly that can also cause the issue or the pump may not be running properly? Curious to see if there's a way to drain pressure from the pump system in order to test it when I go to pick it up.

 

The trunk actuator is probably bad, I have to repair them on almost every R230 I see. That said, it shouldn't affect the locks. A few failed soft closes on the trunk will disable that circuit, but allow the rest of the locking functions to continue. It is more likely the PSE module causing door locks and trunk latch to both be inoperable. New pumps list for $1200, but you can normally replace a motor or impeller and fix it instead of replacing.

 

A 550 at $ 18.000 with these issues to me sounds like an expensive deal. Putting it mildly.

 

This ended up being correct. Replaced the actuator and top was fine. Locking system, I'm not sure. I think when the codes were cleared after replacing the batteries the others have gone away. Picked it up for 18.9k after everything was fixed. I figured that's a good deal given everything is working perfectly with no issues now. Seems the actuator and locking issues were unrelated with the latter likely just due to a battery or voltage issue. Hopefully it wasn't the PSE as if that comes back up again I'll end up having to replace it, too. Is it possible that the PSE can be reset in some way and then have a problem again?

 

May be a battery drain causing the lock issues. If the rear battery gets too low, the remote unlock will not work and keyless go will not work unless you first insert the key to wake it up. Inserted key will work normally. Even with a new battery, a bad drain will run it done in a few days and excess drain is a very common problem on these.

 

Thanks, yeah I gathered it could be it - meaning a new batt wouldn't solve whatever caused the battery replacement necessity in the first place. I don't have a multimeter here, so I can't check. Just a matter of time before finding out if the battery dies again! Do you think that the actuator could have been causing the drain? That's exactly what was happening. Is there a way to maintain charge in the battery, ie. battery tender?

 

@MikeJ65 Thanks for bringing your knowledge here! Battery drain would make sense, and from reading up it seems like drain issues are common on these.

I suspect (but don't really know how to diagnose) that there could be an issue with the PSE pump. My understanding is the locks and the massage system are all on the same line. I've noticed a couple times while driving that I'll randomly feel the massage seat come on for a brief moment before going away again. Between that and the locking issue, I'm wondering if it could be related to that system. Does anyone know of an easy way to see if it is operating normally? I don't understand well how the pump, locking system, and battery would be related. I think that maybe the trunk actuator is on the same system, so maybe they replaced a perfectly good actuator.

I've taken it in to Steve's Beemer & Benz (I don't know the shop yet, first time) in SD. Asked them to run it on their STAR diagnostics on it. They asked me not to tinker with it before taking it in, so I haven't checked any fuses or anything and am waiting to hear back from them, although my understanding is it isn't time consuming to check the pump (but I could be wrong).

 

Shop told me the Voltage on the auxillary battery is 3.4 and the car is showing a ton of electrical faults. The battery was is a Mercedes replaced in april and is a March 2024 battery, but they are saying the battery is bad. Gave them the invoice showing the battery was replaced and they are replacing under warranty. I don't think that will fix the issue.

Shop owner says he pulled up some system on Alltech and it shows that the car previously had the PSE and trunk actuator replaced last year. I didn't know it could do that, as I would assume that information is not public information. Is that a thing?

 

Most of the shop systems share repair data with other shop systems and third parties like Carfax. It is actually to your advantage because you have a record of maintenance and shops have a record of what has already been done.

If the pump and actuator were replaced a year ago, I would suspect the air line from the PSE to the actuator. That line runs along the rear of the trunk floor, turns at the right side and goes up the to the tubular frame, forward along the lower frame to the frame locks, back along the top half of the frame to the trunk lid and eventually the actuator. I would start checking at the ends and at where it has to bend. The actuators are a terrible design, but should last more than a year. A leak by itself should not run your battery down, but if something is keeping the CAN bus awake, the PSE might be part of the problem. You can pull f54 to disable the PSE and see if that helps battery drain.

Also, a low consumer battery will throw probably 40 codes, so it looks bad when you run a scan, but you probably only have one or two systems actually causing the issue.

 

Thanks @MikeJ65 - Took it to Steve's Beemer and Benz in San Diego.

They warrantied and installed the new battery. Ran a diagnostic after. Called and let me know the car was working properly and good to go. They say the passenger SAM needs to be replaced and I need to take it to Mercedes to do that because it needs to be coded to the car. That was on Friday the 24th. Today (Monday the 27th) I go out to drive to car to see how it's doing. Remote won't unlock it like usual. I get in and start it using the physical ignition like usual, except this time instead of what normally happens (car shows the yellow triangle for about 20 feet and then goes away), I have a red message saying there's a bad battery / alternator and to shut the car down. I shut it down and sat in the car for a moment and could hear some component clicking lightly and repeating itself. Not sure if it's causing the drain or if it's something else.

Very frustrating to have taken it to a shop and have had it come back worse than when I took it in. I don't know what they did wrong, but there's no reason it should have gotten worse by replacing the battery as far as I can tell, given the battery was replaced a couple of months ago. Nothing quite like spending $330 to receive your car in worse condition than when you took it in. I read something about accessing a fuse if the car is jumped wrong and it looks like a giant pain in the ***.

I asked for a printout of the report and got a Midtronics printout. I thought they had the STAR system, so not sure why it says Midtronics. Report has low voltage errors everywhere. Shop owner said the trunk smelled a bit of mildew and that I need to check that out. The printout says that the driver SAM has a communication fault with component H3 (alarm) and the passenger side sam is "defective" but also that it has low voltage. To me it sounds like the tech was lazy, told me what the report says, and sent me on my way instead of trying to figure it out. To me, if the brand new battery has died within 3 days, there is some other problem than the passenger SAM. Something is causing a hell of a lot of drain, I imagine. Enough to kill the first battery off completely and then enough to drain this one in 3 days.

I don't know if the passenger SAM actually needs replacement or if that's just a symptom of a deeper problem, potentially resolving itself when the deeper problem is fixed. At this point I might have to just take it to Mercedes and see what they say, as I don't know a good indy shop. Clearly the one I took it to was not helpful.

 

It sounds like you found a shop that is totally unfamiliar with R230s, or they would be fully aware of the battery drain issues on these cars. I agree 100% that they took the lazy approach. Finding battery drains is tedious and there isn't a flat rate in the book for that one.

As to the battery drain, if you have some basic auto electric knowledge, this might be one issue to tackle yourself. It can take a lot of hours to track it down, but the skills required are not really that great. If you can do some simple wrenching to remove panels and you can use an ammeter, you can troubleshoot this yourself. The first step is to replace or disconnect the alarm siren. If you want an alarm, a new siren is around $120 from the discount dealers. The siren has its own batteries and when these go bad it can drain the consumer battery trying to recharge. Lack of communication to the siren almost always means that the batteries have died.

I'm not sure which code you had for the passenger SAM, but there is a common one that reads something like: Module is defective, or if no symptoms are reported this code can be ignored. Kind of like saying "Hey, it's not working! Oh, it is working? Never mind". I've never figured out the logic on that one, but I have seen that code several times when everything appears to be working and took the ignore approach. Also, most issues related to passenger SAM functions are caused by the fuse/relay block, not the SAM itself. The lids on the front SAMs seal OK when everything is properly put together, but the latches are fiddly and tend to break and the seals can fall out of place. Bottom line is that it is common to see corrosion issues with them. If you pull a couple of relays and see a lot of green corrosion, I would start looking for a replacement.

In San Diego, there have to be at least a half dozen independent shops that understand the car and are, quite frankly, better at fixing them than the 20-something techs at your Mercedes dealer. As I told someone a couple of days ago, find a shop owned by some 50+ mechanic that has about 20 Mercedes of around the same vintage sitting around their lot. You won't find them at the top of a google search because they are too busy chasing down problems on 15-30 year old Mercedes to worry about their search engine placement. There won't be a big flashy sign or a fancy waiting room with an expresso machine, but they will have cars stacked up waiting on repairs. One of my local ones uses the reception area as an shop annex and has an R107 with the interior completely stripped and an engine out Porsche crammed it. That's when you know you found the right place.

 

@MikeJ65 I think they're used to working on older cars. They have a number of BMWs and Mercedes sitting around, mostly older. My guess is they don't work on the newer cars much. Owner is easily 50+ but I went into the shop to meet some of the techs and there seemed to only be one Mercedes trained tech, and who knows when he started working there. Owner doesn't work on cars anymore. I think they somehow blew a fuse as well. Pretty barebones shop so my expectations were moderate but hopeful.

I don't have any tools here, so I guess I'll be buying a multimeter later today. I used to work on my own cars all the time, so I will be able to track it down but would like to avoid pouring hours into it if I can.

Codes are:
B1000 Control unit N10/8 (Passenger-side SAM control module) is defective. If no customer complaint exists, the fault can be erased.
B1010 The supply voltage of the control unit is too low (undervoltage)

Details are:
Remedy :
- Disconnect battery G1/4 and battery G1/1
- Replace component N10/11 (Pass SAM)
- Reconnect batteries
- Restart DAS
- Startup N10/11
- Carry out operational check

Yes, I agree on the young tech issue. Most of the guys at our dealership were transitory with decent turnover. We had two master techs who were the guys I would hang out and chat with. I need to find a shop with the 2003+ cars as that shop clearly was better versed on the older ones. Lots of guys out there working on the pre 2003 cars. I was referred by a friend to a guy locally who has no diagnostic system and is a "mercedes whisperer" - you know, one of those old school guys that does things by feel. I'll take it to the dealer first since those guys are YMMV.

I wish I could find a shop like that. The younger guys all focus on AMGs and the older guys stay away from the post 2003 is my impression. Maybe I should just put more time into looking for a better shop, but the dealer may be the easy way out, especially if the SBC pump is bad and needs to be warrantied. Guy who sold me the car is supportive and checking in with prior owner to get more information.

 

 

@MikeJ65 Took it to Mercedes and they diagnosed that the FR SAM needs replacement. Their quote is $2200. He said to replace it and go from there. I'm a bit conflicted because that's two shops saying it needs replacement as a first step, but I fundamentally disagree.

If the SAM is bad, something caused it to go bad, which to me is the first step. Otherwise you end up with another dead SAM.

I could pick it up and then start rummaging around to find a fix, but if I actually do need to replace the SAM through the dealer then it will all be a time burn for me. Any thoughts on the legitimacy of their assessments? My gut says get the car, look around, and see if it is something else before spending $2200 on what a shop claims needs to be done. Too many experiences with too many shops throwing parts at cars. However my gut is based on the other cars I've owned, mostly Japanese and a few BMWs, but I've never had experience with a Mercedes before. I'm not putting you on the hook for anything, but in your experience do you think it makes sense to diagnose or just throw the SAM in and see what happens rather than start pulling pieces off and digging around?

To me it sounds like the likelihood of a SAM going bad is very low. I would assume that the shop would be capable of checking the different components connected to the SAM and checking drain with different modules connected. I reviewed the tech's notes online, and there's no mention of checking voltages or checking fuses. Just the generic young tech saying he hooked it up to the computer to see what it says. Side note: not to mention using the world "analyzation" which is a terrible sign. He also said he let the car sit in neutral and it turned itself off without even saying whether the car was running or not. Low level tech.

Also, if the SAM is indeed defective, wouldn't that be due to something damaging it? Aside from water ingress the only thing I can think of is that something was trying to draw so much power that it torched it, but I would assume a fuse or something would stop that from happening unless the SAM isn't designed very well. To me it would make sense to first check fuses and then changes. I'm going to call Mercedes and ask why that wasn't done and whether or not they'll put my old SAM back in and refund parts cost if it doesn't fix it. I imagine they will tell me to **** off with that suggestion, but I think it's worth asking to see how they respond. Not sure how quickly I should pick it up.

 

If there is an issue with the SAM, it is probably corrosion where the fuse block attaches to the SAM. The dealer will probably want another $1500 to replace it. Then they will run the scan and send the car home like your indy did (still with battery drain). I don't replace the SAM for that B1000 code unless some function it is responsible for isn't working.

Step one is still to replace or disconnect the alarm siren.

Step two (if necessary) is to isolate the current draw and eliminate it.