Interior CanBus (B) dowm
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GL420 CDI 2008
Interior CanBus (B) dowm
Hello everyone,
I am the happy owner of a 2008 GL (X164) 420 CDI (WDC1648281A367830) almost brand new (500k km :-)). Everything was working fine (full options), until recently the automatic hatch fails. It only opens with the handle, but refuses to open with the interior button or the key - in unlocks, and then a few seconds later, as it doesn't move, it lockes again. It also refuses to close, whether with the key or any button on the hatch itself.
I ran Xentry and it appears than my interior CanBus is down (no module found, including the rear SAM). All modules are water free, no corrosion whatsoever, they all look very nice (those I had access to - N93, N121/1, rear SAM and a few more). I have started to check the CANBus wiring, but it's a pain, and I don't know where the end resistors are...I have no resistance at all between Can H and Can L (battery disconnected). I though the central gateway might include a resistor, but no luck (or maybe the resistor are only activated electronically? In such a case, how to diagnose the CAnBus? - I don't have an oscilloscope :-(.
Well, any idea very welcome, thanks in advance,
Best regards,
JF
I am the happy owner of a 2008 GL (X164) 420 CDI (WDC1648281A367830) almost brand new (500k km :-)). Everything was working fine (full options), until recently the automatic hatch fails. It only opens with the handle, but refuses to open with the interior button or the key - in unlocks, and then a few seconds later, as it doesn't move, it lockes again. It also refuses to close, whether with the key or any button on the hatch itself.
I ran Xentry and it appears than my interior CanBus is down (no module found, including the rear SAM). All modules are water free, no corrosion whatsoever, they all look very nice (those I had access to - N93, N121/1, rear SAM and a few more). I have started to check the CANBus wiring, but it's a pain, and I don't know where the end resistors are...I have no resistance at all between Can H and Can L (battery disconnected). I though the central gateway might include a resistor, but no luck (or maybe the resistor are only activated electronically? In such a case, how to diagnose the CAnBus? - I don't have an oscilloscope :-(.
Well, any idea very welcome, thanks in advance,
Best regards,
JF
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Joined: Aug 2018
Posts: 409
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From: Kelowna, BC
08 GL320 CDI
My rear hatch didn't fully open when I first got mine as well (over 7 yrs ago now) It was an easy fix.
It was the hydraulic fluid level was low for the rear hatch piston. (there is a hydraulic ram on the passenger side of the hatch, under the rubber boot.)
The power unit (pump and motor) is located in the spare tire area, under the carpet. Just open it up and check the fluid level. You have to remove the pump and hold it vertically to check the fluid.
But also check to see WHY the fluid is low. I couldn't find any leaks on mine and has been working since.
It was the hydraulic fluid level was low for the rear hatch piston. (there is a hydraulic ram on the passenger side of the hatch, under the rubber boot.)
The power unit (pump and motor) is located in the spare tire area, under the carpet. Just open it up and check the fluid level. You have to remove the pump and hold it vertically to check the fluid.
But also check to see WHY the fluid is low. I couldn't find any leaks on mine and has been working since.
Last edited by Sallad; Aug 3, 2024 at 05:46 PM.
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GL420 CDI 2008
Hi Sallad,
Thanks for the feedback, but it's not the pump :-) As a matter of fact, I took it apart, replaced the oil and bled it, it works like a charm! It seems that all elements are in order, except the warning bip :
JF
Thanks for the feedback, but it's not the pump :-) As a matter of fact, I took it apart, replaced the oil and bled it, it works like a charm! It seems that all elements are in order, except the warning bip :
- when pressing the key or the button inside the driver door, the lock unlocks, and after a few seconds, locks again. But no rise of the hatch. At least we know both the button and the remote trigger are OK
- when I use the handle on the hatch, the lock unlocks, then the pump starts and the hatch goes all the way up, as it should, both closing buttons turn red, so the pump is working
- but no way to close it, except by hand.
- looking at the electric diagram from WIS, it looks to me as if the N121/1 module does its duty when it received the trigger from the handle, but is not receiving the proper information from the rest of the car
- and as I said, there is failure on the interior CanBus when I run Xentry, so I am stuck :-( And because Xentry doesn't see any module on the interior CanBus (except the Gateway), I would first try to restore it, thus my question about resistors :-)
JF
Senior Member
Joined: Aug 2018
Posts: 409
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From: Kelowna, BC
08 GL320 CDI
I remember having issues like that when I first changed my fluid. It's like the fob, rear hatch and the switch in the drivers door were all out of sync with each other. It's been a few years now, but if I remember correctly, I had to cycle through opening and closing the hatch with each device to get then all synced up.
Like manually open the hatch all the way by hand, then try to close with the fob or the door switch. Took quite a few tries.
Like manually open the hatch all the way by hand, then try to close with the fob or the door switch. Took quite a few tries.
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GL420 CDI 2008
Thank you Sallad,
I'll try that again (did a few tests already, no luck), and while I am at it, I'd really like to fix this interior CanBus issue (everything is working, but iy's a pain when it comes to diagnosis!).
Speaking of which... I ran though the electric diagrams (never seen a car that complex, electronically speaking!!
), my understanding is that there are 4 "hubs" (X30/7, X30/6, X30/5 and X30/4). I have checked continuity, it's fine, no shortcut, between Can-L/Can-H or to the ground or the power.
My idea : disconnect all the ECUs, only leave the lines between the hubs, let the CGW connected, connect Xentry/DAS and then connect one module at a time and see what it gives... My fear is : might I break something doing so? And if I understand right the CanBus, there should be 2 resistors (120Ohm) on the line. Assuming that there is one in the CGW (not sure though), where is the second one? Will it work without this one connected?
Thanks in advance again
I'll try that again (did a few tests already, no luck), and while I am at it, I'd really like to fix this interior CanBus issue (everything is working, but iy's a pain when it comes to diagnosis!).
Speaking of which... I ran though the electric diagrams (never seen a car that complex, electronically speaking!!
), my understanding is that there are 4 "hubs" (X30/7, X30/6, X30/5 and X30/4). I have checked continuity, it's fine, no shortcut, between Can-L/Can-H or to the ground or the power. My idea : disconnect all the ECUs, only leave the lines between the hubs, let the CGW connected, connect Xentry/DAS and then connect one module at a time and see what it gives... My fear is : might I break something doing so? And if I understand right the CanBus, there should be 2 resistors (120Ohm) on the line. Assuming that there is one in the CGW (not sure though), where is the second one? Will it work without this one connected?
Thanks in advance again
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Mercedes gl450
I saw a similar post several months ago. In that poster's case, it turns out the bump stops on the gate were worn or out of alignment. As a result, when the hatch was opened other than by the handle, the hatch did not pop out sufficiently to let the system know the gate was open and, therefore, did not activate the strut pump. He replaced the bump stops and all worked well.
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GL420 CDI 2008
Thank you Elbeau,
That's an idea I like, but it's not that :-) When I use the handle, in fact I just pull it (squeeze it really), without pulling the hatch itself (my grand daughter, who is 5, can do it :-) It unlocks the hatch and then opens as it should. I also tried, when using the key, to open the hatch just a little more (in case the angle detection was at fault), but no luck... I'll look for the post you mention anyway :-)
Thanks again,
That's an idea I like, but it's not that :-) When I use the handle, in fact I just pull it (squeeze it really), without pulling the hatch itself (my grand daughter, who is 5, can do it :-) It unlocks the hatch and then opens as it should. I also tried, when using the key, to open the hatch just a little more (in case the angle detection was at fault), but no luck... I'll look for the post you mention anyway :-)
Thanks again,
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Mercedes gl450
Thank you Elbeau,
That's an idea I like, but it's not that :-) When I use the handle, in fact I just pull it (squeeze it really), without pulling the hatch itself (my grand daughter, who is 5, can do it :-) It unlocks the hatch and then opens as it should. I also tried, when using the key, to open the hatch just a little more (in case the angle detection was at fault), but no luck... I'll look for the post you mention anyway :-)
Thanks again,
That's an idea I like, but it's not that :-) When I use the handle, in fact I just pull it (squeeze it really), without pulling the hatch itself (my grand daughter, who is 5, can do it :-) It unlocks the hatch and then opens as it should. I also tried, when using the key, to open the hatch just a little more (in case the angle detection was at fault), but no luck... I'll look for the post you mention anyway :-)
Thanks again,
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Joined: Aug 2018
Posts: 409
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From: Kelowna, BC
08 GL320 CDI
...just brainstorming here... maybe when the manual handle is used, it "bypasses electronically" those sensors on the sides?? So it will react differently when you open it with a switch? I dunno
