2004 Mercedes Benz SL500-SRS Module Replacement
Mark: Hi it's Mark Bossert, producer of the Pawlik Automotive Podcast and we're here with Bernie Pawlik, Pawlik Automotive in Vancouver, 20 time winners of Best Auto Repair in Vancouver and servicing and maintaining cars in Vancouver for 38 years, and we're talking cars, how are you doing this morning Bernie?
Bernie: Doing very well.
Mark: So, today's victim, 2004 Mercedes Benz SL500, kind of a classic Merc, that had an SRS problem. What was going on with this vehicle?
Bernie: So this vehicle came to our shop, the SRS warning light on the dash was on and that needed to be serviced and replaced, other than that, the car was in great shape and running well but the owner wanted that item fixed.
Mark: So, what's the SRS? Super Real Specialness.
Bernie: Yeah, well no, it's a little more boring than that. It stands for Supplemental Restraint System and kind of a fancy word for the air bag system, but there's a little more to the air bag system than just the air bags. And depending on the car, of course air bags have gotten more and more sophisticated and restraint systems over the years, originally they just came out and there was an airbag for the driver, that was kind of the original start to it and then they put one in for the passenger and then they started putting side airbags and then of course a lot of them were a little too powerful or they'd go off at a small accident, people would get hurt quite badly from the airbag, so they've become very sophisticated over the years and the other thing they've added, part of the restraint system is seatbelt tensioning. So what happens when you get in a collusion is that the seatbelt will actually pull tighter.
These things are all timed down to the millisecond, the airbag blows off, the seatbelt tensioner pulls you back so you don't get wacked so hard, but it all kind of keeps you in place and I mean, these things do save lives and reduce injuries drastically. So the SRS module basically there was a warning light on, when the light's on the system may or may not operate, so the interesting thing is you don't know whether it's going to go, whether it's not and it's one of those strange things because you don't need it until you need it and hopefully you never do. It will only ever work during an accident but if the warning light's on, the system's seeing a fault and a problem.
Mark: So how did you test and diagnose this issue?
Bernie: So, scan tool is the way to go. We have a very good quality scan tool, it works well with Mercedes, so we scanned it and found there was no communication with the SRS module. So there was our first problem there, whether there was anything more we couldn't know because the scan tool wouldn't communicate and just to be sure it wasn't a fault with our scan tool we have other brands of scan tools, we plugged them in and there was no communication either, so the next step is to access the SRS module, which is located under the console, it's a bit of work to get to and then test some of the key wiring components, like make sure it's got power, make sure it's grounded and then there's a communication network called CAN, it's a controlled area network. There's some wiring to that network and just to make it's actually getting the proper signals, so after doing all the lengthy testing we verified that everything wiring wise was good. Basically making the module the fault, so we replaced the module.
Mark: So any options available for parts for this vehicle?
Bernie: Well let's just do a quick little picture show here. So here's the SRS module, I mean nothing fancy to look at really, it's a little box about four inches square, I don't even have a picture wiring connector but it's got about I'm guessing a hundred wires that go in and out of it over in this area here of the module and there's an arrow, it actually has to be installed in a certain direction. You see it's got three bolts in different patterns, so you probably can't even bolt it in the wrong way if you tried. But there are accelerometers and things inside the sensors that can detect collisions and things like that. So the repair, that's the question you're asking, is that correct?
Mark: No, where do you get this part from?
Bernie: So, unfortunately the only option is the Mercedes dealer. You can only buy this module brand new and you can only buy it from a Mercedes dealer and the reason why is once you program the module for the vehicle you have to initialize the module through a proper scan tool. You have to set all the perimeters, does it have emergency calling, some of these cars basically if the airbag goes off it'll call a call centre somewhere and alert them that your car's been in a collision, it's kind of like GM OnStar, it'll do that.
So does the car have that option, does it have knee airbags, these are some of the questions that are asked when you program the module, but once you put the VIN number in the vehicle, once you initialize it for the car, it's basically locked in and you cannot change it and put it in another car, which in my opinion is absolutely ridiculous that you can't take a used module, reprogram it for something else but for some reason in Mercedes wisdom they've decided that once you lock it into the car, it'll only work on that car and never on anything else. I can talk about this a little more because I think to myself, why would they do such a thing? It's like, if we think of Mercedes on the good side, they don't want anyone to screw something up.
They want the system to be 100% reliable for that car, so you buy this fine German quality car and you put the right part in it and it's going to function as advertised, whereas if you were going to take a used one maybe there's a risk that it wouldn't be programmed properly, so from that point of view I can see why they do that, but from a perspective of waste, if you think of all the cars out there that probably use the same module, there's hundreds and thousands of them sitting in auto wrecking yards right now and their only fate is just to be disposed of or recycled because you can't use it in another car, and why wouldn't you?
It should be so simple to just erase the programming, redo it. Before we initialized it, I said it had a knee airbag when the car actually didn't and it's an error code and it wouldn't allow me to program it, so the car's actually smart enough to actually tell you what to put in the module. Anyways, that's my little rant about this particular module, but unfortunately it makes for quite an expensive repair as opposed to what it could be just because you have to buy the module new.
Mark: So this car's getting on over 15 years basically but it's really a nice model, is it worth hanging on to?
Bernie: Well this one certainly is, believe it or not this vehicle we worked on has actually only got 14,000 kilometres on it and if you put that into miles I think that's like, 8 or 9,000 miles, it's like a brand new car and it was amazing driving it because it really was as tight of a feel as a brand new car. It was beautiful and the owner of this vehicle apparently had previously passed away and the car sat in the garage for ten years, one of those kind of neat stories but this one was great.
But these are complex cars, there's a lot that can go wrong with them, so you just need to be prepared, and go hey, it's a nice car. You can buy it for a very good price, because they tend to depreciate nicely but over time you'll spend a lot of money repairing it. This module job was a couple thousand Canadian dollars over that by the time we diagnosed it, replaced the part, reprogrammed and did everything that needed to be done, so it's a pretty pricey repair but the owner will never need to do that again, but they'll be something else, so you could probably count on spending $2 to $4,000 dollars or more a year to maintain this car if you drive it around.
Mark: So there you go, if you're looking for a Mercedes repairs in Vancouver, the guys to see are Pawlik Automotive, you can reach them at 604-327-7112 to book your appointment. You have to book ahead, they're really busy or check out the website, pawlikautomotive.com. Pawlik Auto Repair is our YouTube channel, got that mixed up really well and of course thank you so much for listening to the podcast, we really appreciate it and thank you Bernie.
Bernie: Thank you Mark and thank you for watching and listening, we really appreciate it.