DanielE320

On my way home my car started but stalled at a 4 way stop 5 minutes into the drive home. Like most places it has been abnormally hot today. Red and Green lights on rear view mirror are going crazy when I crank it, which makes me think it is a security/imobilizer issue. However, tach does not move,which makes me think maybe a crank senor issue. Does anyone know if a bad CPS will cause the tach not move when cranking. I know that is the case on other cars but wasn't sure if that is true with Mercedes. I Don't hear the fuel pump run either when I turn the key. But that is not a fool proof as maybe it is just hard to hear.

Plutoe

I do not think that you have enough diagnostic information to boldly suggest that the CPS is faulty with out producing a CEL, I know bla bla bla said so therefore it must be true.

I can think of a number of modules that could produce those symptoms. Get the car quick tested before you fall in to "let's try this part next" snydrome.

PS My tach never moves on crank

DanielE320

I don't know if I have correct fuel pressure. However, I do have fuel at the test valve. I relieved the pressure and cranked the engine and checked the valve again. Pressure in the fuel line resumed. I ordered a new bosh cps sensor. It was not that much and even if it doesn't need the CPS now I feel it is worth replacing it for the peace of mind. These seem to be a weak link that strand you without warning on most makes of cars. I don't own a code reader as I usually have the dealer or parts store pull the codes when necessary. In the 120K miles that are on it, this is the first time that the car has ever been undriveable. The CEL did come on while driving it prior to stalling.

I have contacted a nearby shop that specializes in MB and it will likely go in to the shop next week. I have the inline 6 E320. Is the sensor located at the rear of the engine in bell housing? Is the sensor acessable from above or will the car have to be lifted up? I would like to elimintate this as a possible cause prior to going into the shop. Thanks!

DanielE320

Update, on my first attempt to start the car today which is much cooler today. (68 for a morning temp) It cranked fine. Red and Green lights on mirror alternated flashes. But No Start!! Turned the key off and again attempted to start it. While cranking it this time I noticed that the Red and Green lights on the mirror were not flashing. It started and drove it for a little bit and let it run. I ended up shutting it off and havent tried to restart it. I just have a blade key. No remote! I have been using this key for nearly two years.

cyberflyrg

Daniel, I just replaced the CPS in my 99 E320 and it solved my problem. My 99 was stalling, and restarting then would run for days and start it all over again. Had it towed 3 times in 4 months. The CPS does not throw a CEL or code, at least mine didnt. It just stops working or intermitently works.

CKonstantin

Don't rush with the CPS. I had a similar problem. The flashing lights indicate that Driving Authorization failed, and a very common reason for that is the K40 relay not supplying power to the ECM and causing it to malfunction. So first pull your K40(in computer box near right fender, it is the only module with fuses on it) remove the casing and give it a good look-over use a good light and a magnifying glass if necessary. You are looking for micro-cracs on the underside of the board where the relays are soldered. If you are handy you can re-solder it, otherwise buy a new one. Symptoms are lights flashing and car not starting, sometimes remedied by unlocking it with the key, car only starts when they're not flashing. Can happen when the car is hot or cold and will get progressively worse to a point when they flash at every attempt of starting the car.

Now as when the CPS fails it will usually only happen when the car is hot. Often when you were driving fast and then stopped or slowed down, which causes a spike in temperature.

Hope it helps.

DanielE320

I should have mentioned that it is a 1996. So, it doesn't have as complicated of security system? Well, its not a chipped system. Mine does not have the K40 relay at least so I am told. It does have the A2105400072 relay. It is at a shop they think it is security system related. I ordered a new Key and FOB. However, I always open the car with the key as the remote fob has been inoperable for some time. What is required to swap security computers? Can I install a used computer? Where is the computer located? Thanks!

CKonstantin

You cannot install a new computer, and neither a new key or FOB will help if when you open the car with the key the lights flash as they should(green when opening and red when closing). ECMs are permanently matched to the res of the rest of the security system.

Yes you do have a K-40, your shop might call it something else but A2105400072 is it.

It's failure is very often misdiagnosed. On my car MB dealership verified it and said it was Fine, however when I opened it up I saw micro-cracks in the soldering, re-soldered and it took care of my flashing lights for good.

Take a good look at it before buying anything else it's fairly easy to remove and open up, and it wont cost you a thing to check it.

DanielE320

Prior to towing the car to the shop I did remove the K40/A2105400072 relay. I visually inspected the PCB and it actually looks like new inside no burnt areas or broken solder joints that I could tell. That's not to say it isn't the problem. I only have one key and need another key anyway. I agree it is not the issue. While I do not necessailry want or need a remote start feature. Is it possible to install a remote starter? As the car ages if the security system is going to be a pain and strand me I would rather devise a work around it. If it is possible to install a remote stater I would think that would be the work around the security system that I need or at least the way to confirm the issue. My key does not have a transponder chip. I should have the key today. I expect to report later today that have a replacement key which has not changed the no start status.

Plutoe

It seems that your modification expectations far exceed reality.

Old MB are not easy to correctly diagnose without proper equipment and are expensive to repair!!