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I've had an ongoing issue with my 320 CDI where it is difficult to start in the morning because the ECU isn't getting power. I've changed loads of stuff and have a thread running on the big details of the problem.
One thing caught my attention this morning. While I was having the starting issue I checked a few bits of equipment like headlamps, air conditioning, etc, etc.... I noticed another system not receiving power was the windscreen wiper motor.
So my small question for this sub-topic is if anyone knows what common connections are shared by the wiper motor and the ECU. I guess we would have to see a diagram to figure it out... but I don't have any of those for the W211.
Not you again-----like we keep telling you and you are not listening----voltage flows when your key is in various positions and then switched on by various system relays and switches to the consumers like wipers, windows and ecu bla bla
What more dont you want to know.
If I recall correctly your last reply on another thread of mine was also incorrect and unhelpful.
Just replaced it. The old battery was probably okay as well. Replaced the little aux battery also.
Thought it might be battery related, because weak batteries can cause electrical systems to shut down in some priority sequence -- some systems still operate and others get disabled. Have you run an OBD scan?
Thought it might be battery related, because weak batteries can cause electrical systems to shut down in some priority sequence -- some systems still operate and others get disabled. Have you run an OBD scan?
Yes, I've got STAR and a third-party code reader and I've done a lot of work on this problem already. I just didn't want to cloud this thread in case it stopped people thinking about the simple question in the title.
Yes, I've got STAR and a third-party code reader and I've done a lot of work on this problem already. I just didn't want to cloud this thread in case it stopped people thinking about the simple question in the title.
Understand -- car electronics have become enormously complicated, but I still look for simple solutions (like a dying battery) first. Generally speaking, secondary systems like wipers interface to a LIN bus, which ties to a CAN bus, which connects to an ECU, which connects to one or more SAMs which contain activation devices (relays or solid state switches) which control the state of the accessory system, in this case the wipers. An OBD scan should identify faults within the inner systems, such as communication errors between nodes, but won't go as far as the last segments -- the activation switch and the activation device. I'd start with the wiper wiring and activation device in the SAM. If there are several intermittent faults in several systems (you mentioned hard starting), maybe there's damage to a SAM unit. Some owners have reported SAM water ingress that causes widespread faults.
Understand -- car electronics have become enormously complicated, but I still look for simple solutions (like a dying battery) first. Generally speaking, secondary systems like wipers interface to a LIN bus, which ties to a CAN bus, which connects to an ECU, which connects to one or more SAMs which contain activation devices (relays or solid state switches) which control the state of the accessory system, in this case the wipers. An OBD scan should identify faults within the inner systems, such as communication errors between nodes, but won't go as far as the last segments -- the activation switch and the activation device. I'd start with the wiper wiring and activation device in the SAM. If there are several intermittent faults in several systems (you mentioned hard starting), maybe there's damage to a SAM unit. Some owners have reported SAM water ingress that causes widespread faults.
I've got two front SAM units and have swapped them around a couple of times and the fault is identical no matter which SAM is installed.
If you do not like Star Diag conducted tests ( I would start with the EZS voltage circuit) you can try to verify the voltages to the engine ECU with a multimeter and schematics.
Any engine ECU has the same logic, on the connector 2 ( the small one ).
1 - 3 very important ground connections
2 - Circuit 15 - the positive voltage for starting the ECU, the digital part, bootloader, diag capability, etc.
After booting, the ECU will make a digital handshake with the EZS and if key, security, etc is OK then the ECU can be open with the Diag system. If not you have to go back at - 2.
3 - Circuit 87 - normally 3 wires should carry the voltage supplied by the SAM over fuses and relays to the ECU. Those relays are triggered by the ECU over a negative feed to the SAM/Relay Fusebox.
Circuit 15 goes live as other systems which should also work are fine. Things like electric windows, headlamps, air-conditioning... all come on but the wiper motor and the ECU do not turn on. When you run a diagnostic the diagnostics machine reports it cannot communicate with the ECU.
The ECU and the wiper relays both go through the front SAM. They may share a common power supply or common ground wire which is why those two items in particular are off when everything else is on.
There's a control unit inside the wiper motor, if I remember correctly driver side SAM would whine if there is no connection.
Might be just coincidence that wipers are acting up now. Pull the cowl and measure voltage from the connector to be sure.
Does your washer work, and have you checked signals from the stalk?
Your logic is all wrong or you have difficulties understanding the starting circuit which energizes some key functions like the ECU and SAM bla bla but not the wiper motor which is energized when you switch on the the wiper relay located on the SAM and once again the ECU has nothing to do with the wiper system and or function
If you dream that the ECU has no power then simply locate the power on socket/pin on the ECU and determine the voltage with key on and off---very simple
You're unhelpful and wrong with every comment. How can you say the wiper motor and ECU have nothing in common as some sort of useful insight? Both are powered by the battery ultimately. So from the battery to the wiper motor or the battery to the ECU... they are not wired with separate connections between each item and the positive terminal on the battery... so further up the food chain they do converge and to pretend otherwise is absurd.
There's a control unit inside the wiper motor, if I remember correctly driver side SAM would whine if there is no connection.
Might be just coincidence that wipers are acting up now. Pull the cowl and measure voltage from the connector to be sure.
Does your washer work, and have you checked signals from the stalk?
The wipers work normally if the ECU is getting power. So when the engine is running the wipers are fine. If the ECU has power and the glow plug light comes on then I can operate the wipers.
Interestingly, if I activate the wipers using the diagnostics machine they will run until I turn to ignition position 2 and then they stop.
You're unhelpful and wrong with every comment. How can you say the wiper motor and ECU have nothing in common as some sort of useful insight? Both are powered by the battery ultimately. So from the battery to the wiper motor or the battery to the ECU... they are not wired with separate connections between each item and the positive terminal on the battery... so further up the food chain they do converge and to pretend otherwise is absurd.
Rather than shoveling rights wrongs back and forth, how about some informative explanations and supporting evidence? My interest is learning how things work.
Where to check? I believe I've seen varying fluctuating voltage into the front SAM. There is a large red supply lead clamped to the front of the SAM and I tested there. It was only a brief test and after checking it the car started so had no opportunity to check further. I had something around 3v showing when really it should be battery voltage.
I guess potentially the answer to this question is that the front SAM doesn't do much you can see in the cabin apart from the wiper motor and the ECU. It also does the instrument cluster and the ESP module. So perhaps the power supply into the front SAM is what's causing it.
Where to check? I believe I've seen varying fluctuating voltage into the front SAM. There is a large red supply lead clamped to the front of the SAM and I tested there. It was only a brief test and after checking it the car started so had no opportunity to check further. I had something around 3v showing when really it should be battery voltage.
I guess potentially the answer to this question is that the front SAM doesn't do much you can see in the cabin apart from the wiper motor and the ECU. It also does the instrument cluster and the ESP module. So perhaps the power supply into the front SAM is what's causing it.
Your measurements was not relevant, as you were not so convinced.
Anyhow, if you are talking about Driver Side SAM ( 211 has 2 Front SAM's), then the red 10mm cable came from F33 fuse box, from a 200Amp fuse numbered 78...if the engine is 642.
Do you agree to use Xentry or you want to continue with the multimeter?
I think I saw F33 under the carpet in the drivers footwell. I see the main supply from the battery comes to that junction point where there are some fuses before it spurs off to other parts of the car.
Makes difference, of course. It's on different older chapter in WIS or DAS.
Can you measure again the main voltage on SAM ( also if you are kind enough, tell us if you are referring to left or right Front SAM)
Left is always left even if the steering is on the wrong side and is considered as you are inside the car facing forward
I think I saw F33 under the carpet in the drivers footwell. I see the main supply from the battery comes to that junction point where there are some fuses before it spurs off to other parts of the car.
In the posted picture, the F33 name start with "rear" fuse ...
Makes difference, of course. It's on different older chapter in WIS or DAS.
Can you measure again the main voltage on SAM ( also if you are kind enough, tell us if you are referring to left or right Front SAM)
Left is always left even if the steering is on the wrong side and is considered as you are inside the car facing forward
It's a bit difficult as at the moment the fault seems to have gone away. At the moment it starts first time every time just like it used to. If it comes back I'll have a look at the voltages.
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