Hello Kevin,
Sorry for the delay, it’s been a very long day for me today, completely shattered. Anyway, lets just take stock for a moment and look at everything that you have done to date. We can now effectively rule out the hydraulic leak issue given that you have checked and found none, however, there is a possibility that the pump is not delivering sufficient pressure to overcome the weight of the boot lid, especially, when you say that the boot lid is opening and being raised by several inches, this in itself shows the system is attempting to work As I stated earlier, its quite rare for leaks to be found in this area, but that doesn’t mean to say that they don’t leak, on the contrary, but it is very unusual for them to do so. Up to now, everything that we have done is pretty much on a visual basis; however, this is where it now gets extremely technical. The electrical architecture on a CL is the one of the most advanced system on any Mercedes Benz to date.
So, lets answer the questions to the last two posts first. The voltage supply to the PSE pump and the hydraulic pump do not come from the rear SAM control module, on the contrary, the voltage supply to the PSE module is via fuse number 62 - which is a 20 amp yellow fuse and is found in the same fusebox that I provided earlier. The voltage supply to the hydraulic pump is via fuse number 57 in the same fusebox, the two micro relays are switched on/off from the PSE control module. Have a look again at the fusebox layout and you will see the fuses clearly identified, more on this later.
The rear lights - brake lights, reverse light, fog light and indicators on the n/side and o/side rear of the vehicle only are all controlled by the rear SAM control module, so yes is the answer to that question. Also, the boot lights under the rear parcel shelf, the one in the boot lid, the number plate lights and the high level brake lamp in the boot lid are all controlled once again by the rear SAM control module. As you say, we can look at those in another thread sometime.
The drivers door switchpack with the boot release switch is illuminated to identify that the boot lid catch is actually open – what you could do is mechanically close the catch with a screwdriver blade or something similar and see if the lamp goes out, then press the boot switch release button in the boot lock itself (where you insert the metal key blade) to see if the catch releases, effectively, what we are checking here is the integrity of the wiring loom from the boot lid through the umbilical loom/harness and back to the PSE module. The umbilical loom from the boot lid to the main boot wiring harness runs around a spring tensioned pulley system and is very vulnerable and electrical wires do get broken as a result, an area worth checking much later on.
I’ll condense the next two paragraphs in the interests of brevity - This is how the remote boot opening and power closing system actually operates from the drivers door switchpack, when you actually press the boot release button, this switch is “hard wired” in to the drivers door module, from the drivers door module, a message is then sent over the CAN data bus to the PSE control module to either open/close the boot lid depending upon which way you pressed the boot switch. Once the boot catch is released, (microswitch activated and detected in the locking mechanism) a message is then sent back over the CAN bus to the drivers door module to indicate the boot catch has been released, the rocker switch in the door is then illuminated to indicate to the driver that the boot is open, the very same protocol process is followed when you close the boot lid and the catch is fully closed. This system is very complicated and the PSE module is linked to many of the other modules within the car.
When you operate the boot lid open function from the key fob, then it’s an entirely different scenario. If the boot lid open push button switch is operated on the remote key fob, then the transmitter keysends a signal to the rear window antenna above the rear screen. From here, the signal is then sent by the rear window antennas amplifier module to the overhead control panel module, the one in front of the sunroof with the panel/reading lights etc. The transmitted data for boot lid opening information is then sent from the overhead control panel module to the EIS (electronic ignition switch) control module over the CAN bus. The EIS control module then checks the access authorisation and validity codes of the transmitter key. If access/authorisation is granted and then issued, then the EIS control module sends a data command message to open the boot lid over the CAN bus to the PSE control module. As I said above, its an extremely and very very complicated system and we have to approach it in a logical step-by-stem process, so my apologies for this.
You can check in the instrument cluster sub-menu’s under settings, scroll down to vehicle, enter the vehicle menu and in here is the boot opening height limiter. If it is actually switched on, then turn it off. Do you have an owner’s manual to follow this procedure. Also, you could check the boot opening angle detector sensor (the potentiometer I mentioned in my previous post). It’s located on the o/side just above the hydraulic ram, see attached photo below. You can check to see if the ball joint and linkage are still connected by using a mirror and a torch. The unit is secured to a bracket with two torx screws, undo these and slide it from its bracket. The potentiometer has an electrical connection held in place with two locking tabs. The 3 wires are colour coded as being red/green, which is a 5 volts input supply, brown/green, which is a 3 volts output source back to the PSE module and a ground circuit, which is a brown wire. The potentiometer is an extremely important component and serves two specific purposes, firstly, it monitors the position of the boot lid and therefore informs the PSE module when its at its maximum travel and secondly, it monitors the speed/rate of change when the boot lid is opening/closing. This is also another unit that does actually fail which results in a very similar issue such as yours, however, one has to be very careful here and make sure that it is the sensor and not the PSE module, which it is connected to.
Just to recap and finalise – lets just go over these again: -
Will you remove both fuses, numbers 62 and 57 for the time being and then replace them after several minutes, effectively, cutting the power and then reinstating it.
Also, will you remove the two micro relays that control the pump operation and change them over, its easier if you push up on the relay connector block at the bottom and ease it off its bracket and change right to left and left to right relays.
Once the above has been done, close the boot lid and then we can check if the boot lid actually opens using the push button in the boot lock assembly above the number plate.
In view of what we have covered, the electrical system at the moment seems to be functioning; the communication network is functioning because the modules are actually doing what they are supposed to do – communicating with each other. I have the one or two concerns here Kevin, is the pump capable of delivering the required pressure to overcome the weight of the boot lid and is the boot angle sensor giving the correct feedback to the PSE module, also, is the PSE module actually seeing the data from the boot angle sensor. We could also test the pump in isolation from the rest of the cars electrical system (by-pass) to see if it will raise and lower the boot lid, lets see how we go first, by the way, how are your electrical skills.
Anyway, try the above again and we will see what area we can go in to next, from hereon, it gets extremely complex though and we will have to do a pin-out by pin-out testing procedure to make sure we are getting the right data and voltage levels. I won’t be able to come on the forum at all tomorrow evening, its Friday night and me and my wife always go out with friends, so Saturday afternoon will be the earliest now, so my sincere apologies.
Regards,
Dash1
