Mercedes Repair Questions? Ask a Mechanic for Answers ASAP
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This may be a fault with the electronic ignition switch itself.This is the switch the key inserts into.If this switch is acting up intermittently it will cause all of these faults here and is most common.It will need to be tested and if replacement is needed a dealer will have to replace it as it requires programming/coding after it is replaced.
The other issue is with the front and rear SAM control modules.These can short out/fail internally and cause issues like this as well.Although the electronic ignition switch is most common.
You will need to have fault codes read out of all computers with either a dealers sds machine or a scan tool that will plug in and communicate with all computers in your vehicle to see what codes are set and from there those codes diagnosed to locate and repair the fault.The sds machine or compatible scan tool is also used to observe data and check signals from the electronic ignition switch to make sure it is the cause here.
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I used to work at a Mercedes dealer for over 15 years.Now I do my own work as well as work from here to help customers.The cost can vary all depending on the fault occuring here.This sounds more like the electronic ignition switch (EIS) at fault and this in some cases can cost over $700 to have replaced and will have to be programmed by a dealer or authorized Mercedes repair center in order for it to operate after it is replaced.
It is possible at some point it may fail all together and not allow starting or may cause a stall out and can keep from allowing the vehicle to start again.It is hard to say if this will occur for sure though.
I would have this checked into/tested further to be sure this is the cause here.
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This does sound like low voltage which will cause the electronics to act up like this here.If these are new batteries or a new battery installed this sounds like you have an electrical component draining the battery down.This would need to be tested to see which component is causing this here and requires a multi meter to do this testing as well as the correct wiring diagrams to locate the component on the circuit that has the battery drain at fault.I can post the procedure below on how this is tested but this will require the correct wiring diagram of your model for this here.
I can say I have seen the instrument cluster and the SAM control modules fail internally causing this drain/draw issue needing replaced.
SAM stands for signal acquisition module.They control and monitor several electronics inside and outside of the vehicle.
Depending on if and which are at fault this can run around $700 to over $1000 for replacement.They also require programming to be done by a dealer when replaced.
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The 2002 model is an older model of the 163 chassis and your model is of the 164 chassis so they are different models unfortunately and the bulletins are different.
Unfortunately in order to find the source of the drain this will need tested which can require some time to do (usually anywhere from 2 to 8 hours to pinpoint it with the correct test equipment and correct wiring diagrams).Even if it does require a sam replacement the new sam will need to be set up and programmed by a dealer in order to work properly.
It is best to have this tested to locate the source of the drain then that component replaced.
Unfortunately this may take a day or more to have tested then the part has to be ordered in from there to repair this fault.
The front sam is located under the passenger front seat and it can become wet from the ac drain being clogged or disconnected or from water or a spill in the back seat area.It is located under the passenger front seat,under the carpet which is under the duct work and then under a plastic panel.Once all this is removed there you will see the main large battery and the sam is to the right of it.
The rear sam is located in the passenger rear of the vehicle behind a panel below and to the right of the rear fuse box.
If there is any water in the sam unit the sam affected will need replaced.