|
S80 '98-'06 / S60 '00-'09 / V70 & XC70 '00-'07 General Forum for the P2-platform S60 / V70 / XC70 / S80 models |
Information |
|
Power Seat only moves in One DirectionViews : 537 Replies : 3Users Viewing This Thread : |
|
Thread Tools | Display Modes |
Jun 5th, 2020, 07:28 | #1 |
New Member
Last Online: May 17th, 2022 23:57
Join Date: Jun 2020
Location: Herne Bay
|
Power Seat only moves in One Direction
Hi,
This is a strange issue that I hope someone can help with. I have a 2016 XC70 and it has developed a problem where the power seat motors only move in one direction. Normally I would suggest that there might have been something jamming the motors but the odd thing with this is that all of the controls have the same issue slide, tilt, height etc. all move in one direction but not the other. What I have noticed is when you move any of the switches in the direction that the motors so not move you sometimes get a small blip of movement and then nothing and other times it does nothing. I can hear the relays clicking but no movement. I have done some diagnostics and found the following: Checked diagnostic codes with VDASH and there were a few codes, one said that a motor was short to ground (I believe). And the other said lost comms with the PSM. Cleared the codes and re-checked several times and no new codes generated. Removed the memory module and manually connected power to the motors. They all moved in both directions fine which proves that the motors are basically OK. Plus I think if it was a motor at fault then the other chair movements would work OK. I think its unlikely that all the motors have failed at the same time. This pointed to an issue with the PSM so I got hold of a replacement and it exhibited exactly the same issues albeit VDASH registered an error code saying the PSM software version was incorrect. So the results of this suggest that the motors should be OK and it is more likely a control issue. Swapping out the PSM has (I believe) proven that the PSM is OK. So I'm at somewhat of a loss as to what might be the issue. A couple of other odd things (I believe) that might be indicators or could be contributing to the issue are that: The power seat only works (in the directions that do work) when the engine is running and the doors are closed. This may be correct operation but I would have thought that it would work any time the ignition is on and would not be dependent on the doors. The power window controls in the drivers door also inly work when the engine is running and all doors are closed. This could be unrelated but I don't think it used to do that and I think it only started at the point that the power seat failed. So my thoughts on this are that There may be a relay somewhere outside of the PSM that is triggered by the ignition that could be causing an issue. I don't have any of the wiring diagrams so can't tell. This might explain a link to the window controls if they run through the same relay A ground or continuity issue, this again might explain not functioning when any of the doors are open but it feels like it's a control law issue as it doesn't seem to be based on door position but more based on the closed sensors. A CEM/UEM fault. I'm not sure how the control laws work on the XC70 but the PSM doesn't work at all if the CAN connector is unplugged which suggests another controller on the CAN bus can enable/disable operation and maybe said faulty controller is giving false information to the PSM to stop moving the seat??? I've read a lot of posts on power seat issues but haven't seen anything the same as this. Hopefully someone has some ideas or has seen this before and can help. Thanks in advance. |
Aug 30th, 2023, 21:05 | #2 |
New Member
Last Online: Sep 7th, 2023 07:44
Join Date: Aug 2023
Location: Harrogate
|
Hi, Did you ever resolve this issue? I've got exactly the same problem with mine, all drivers side seat motors only working in one direction, clicking slowly back the other way. Also the thing with the seats only working with the doors closed, I don't remember it being like that before.
I've just finished replacing the door lock motors in both front doors so it seems too much of a coincidence not to be related. I did blow the drivers door fuse when I was trying to test the windows with the door panel off, so I'm wondering if that has caused it. Once that was replaced everything relating to the doors is now working locks/windows etc. |
Jun 7th, 2024, 22:42 | #3 |
New Member
Last Online: Yesterday 19:07
Join Date: Jun 2024
Location: Nashville
|
Solution
Sorry mods for necroing this thread 4 years later BUT i have a solution to this issue i just spent 3 days on.
I am a certified Mechanic that specializes in European automobiles and I have a customers car (17 XC70) with these exact symptoms. Long story short check fuse F3 on the Central Electronic Module, it should be a 7.5 amp fuse. You will have to remove the glove compartment for this. What I found was that pin 1 on the C2 connector to the PSM (green connector) should have power coming from the CEM through fuse F3. Its listed as (To interior lights) on available wiring diagrams but on the factory diagram I could see that power was indeed expected on this pin and was absent with the doors open and low voltage was present with the doors closed. This is because that fuse is shared with the interior lights system and when the lights are commanded on (opening doors) what little power is available gets sucked to the interior light circuit and starves the PSM. This explains why the power seat will only move with the doors closed and requires the engine running sometimes (extra power pushing through?) why it only moves on the one direction is unknown but i theorize the internal workings of the circuit board determine what happens if only 1 source of power is present. I found the F3 7.5amp fuse had failed but not popped. Internal resistance of the fuse was in megaohms when measured. A new fuse put in place and now the seats work properly and indeed the seats should move with the doors open and the engine off. You can check this by supplying power manually (like with a power probe if you have one) to the Red/White wire on the green connector and then trying to move the seat. If it moves then likely the fuse is bad. Last edited by Euromechanic92; Jun 7th, 2024 at 22:48. |
Jun 8th, 2024, 18:00 | #4 |
Premier Member
Last Online: Yesterday 23:29
Join Date: Mar 2017
Location: Manchester
|
could this kind of fault be caused by the fitting of aftermarket led interior bulbs? as iv seen this kind of thing before intermittent seat operation
|
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests) | |
|
|