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Some time ago my wife noticed the passenger seat wouldn't move forward for easy entry, and door buttons wouldn't work either. I looked underneath and found a nice little damn glass container for lip balm or makeup or dunno-what tightly stuck between the seat and the floor. I did manage to take it out and hoped it would be just the fuse. The fuse was indeed blown, but as soon as I inserted a new one, it blew right before my eyes (if it had been someone else's car, it would even be fascinating to watch). Is it a short circuit in the motor winding? I'd appreciate any suggestions on what can be checked (I have a multimeter) and how difficult it can be to repair.
Some time ago my wife noticed the passenger seat wouldn't move forward for easy entry, and door buttons wouldn't work either. I looked underneath and found a nice little damn glass container for lip balm or makeup or dunno-what tightly stuck between the seat and the floor. I did manage to take it out and hoped it would be just the fuse. The fuse was indeed blown, but as soon as I inserted a new one, it blew right before my eyes (if it had been someone else's car, it would even be fascinating to watch). Is it a short circuit in the motor winding? I'd appreciate any suggestions on what can be checked (I have a multimeter) and how difficult it can be to repair.
Thanks!
between the blowing fuse and the seat rail motor theres a control module with power transistors to switch signals as requested position.
There's danger in the form of SRS Connector right next to seat connector - So be advised to disconnect all power before attempting repair.
-- Seat Module is conveniently snapped onto a holding bracket.
-- Take pictures to help guide yourself.
-- Connectors also use a little snap-lock that you will need to press-in to release.
between the blowing fuse and the seat rail motor theres a control module with power transistors to switch signals as requested position.
There's danger in the form of SRS Connector right next to seat connector - So be advised to disconnect all power before attempting repair.
-- Seat Module is conveniently snapped onto a holding bracket.
-- Take pictures to help guide yourself.
-- Connectors also use a little snap-lock that you will need to press-in to release.
-- module may need repair or replacement.
Thanks a lot! Is the module under the seat? On this diagram, is it 300 (control unit) or 270 (TS long adjustment, although I'm not sure it's a control module), or something else?
Yes exactly No#300 is the seat control module located under it.
It is a normally soldered module, not built to fail prematurely under normal useage... without obstacles
Plenty of used junkyard unit should be available for cheap (low demand).
Thanks! I hope I can find it and look for burnt pins/wiring and any visible damage to the module. If everything looks fine, it there any way to check the module itself? Is trying to open it and looking for burnt components inside worth it? Or is finding a used one and replacing it the only option?
EDIT: just thought I can disconnect it and check for short circuit, but I haven't found a wiring diagram yet, so it's not exactly clear which pins to check...
Thanks! I hope I can find it and look for burnt pins/wiring and any visible damage to the module. If everything looks fine, it there any way to check the module itself? Is trying to open it and looking for burnt components inside worth it? Or is finding a used one and replacing it the only option?
EDIT: just thought I can disconnect it and check for short circuit, but I haven't found a wiring diagram yet, so it's not exactly clear which pins to check...
You've already done the advanced troubleshooting!
Module keeps frying fuses as soon as plugged in!
It has a blown component... I was going to write the word transistor but nope, they used relay cubes.
You'll see once its open, if anything's obvious.
You can start searching for a replacement module unless it's the electric motor itself that got charcoaled
Yes exactly No#300 is the seat control module located under it.
Winter was cold, and summer has been quite busy, so it's only today that I've taken a look. The seat is stuck in the forward position (must've been going forward to allow for easier entry to the rear), so the rear bolts are easily accessible, while the front ones are impossible to reach.
Do you know if the the module can be removed without removing the seat?
And is it the one on the photo?
> Set seat position mid way do you can access both front and rear of the module.
> DISCONNECT ALL BATTERIES.
(The seat is loaded with SRS airbags)
> Unplug connectors from the seat front
> release module latches from the rear to pull module out.
Expect this module not to use oxidized solderless pins. Regardless expect "cold solder joints" because the relay collection carry high Amps and need more heat to solder well.
> Set seat position mid way do you can access both front and rear of the module.
> DISCONNECT ALL BATTERIES.
(The seat is loaded with SRS airbags)
> Unplug connectors from the seat front
> release module latches from the rear to pull module out.
Expect this module not to use oxidized solderless pins. Regardless expect "cold solder joints" because the relay collection carry high Amps and need more heat to solder well.
Thanks for the instructions!
Yes, this is front view. So it's supposed to be removed without removing the seat? That's good news. The "set seat position mid way" is not so good news as I can't move it (hence the need to remove the module ), unless I can somehow feed 12V directly to the proper motor (I think I've found the wiring diagram, looks like the pins that go to the fore/ant motor are on the back in the 14-pin plug), but I'm not sure it's a good idea.
Just to make sure I'm reading it correctly, should it pull out to the back?
Yes, this is front view. So it's supposed to be removed without removing the seat? That's good news. The "set seat position mid way" is not so good news as I can't move it (hence the need to remove the module ), unless I can somehow feed 12V directly to the proper motor (I think I've found the wiring diagram, looks like the pins that go to the fore/ant motor are on the back in the 14-pin plug), but I'm not sure it's a good idea.
Just to make sure I'm reading it correctly, should it pull out to the back?
Yes, this should come out back but you can also lift it out of its cradle and have a chance to go above or around the cradle...
2x locking pins
the pins I circled above stop forward motion... remove backwards: towards the back.
You seat is stuck...hard to see anything :
Spie on the other front seat for what you cant see.
After all you will agree it is real basic:
un-latch then slide out.
Last edited by CaliBenzDriver; Aug 18, 2025 at 01:08 PM.
After all you will agree it is real basic: un-latch then slide out.
After half an hour of blindly unplugging the pins and then applying some brute force in various directions I've managed to pull it out. No signs of severe (or any actually) electrical damage though, unless I'm missing something. Below are some pictures, the whole module first and then zoomed on various parts. And I'm not sure what to do next...
I can connect the battery and check if the fuse doesn't blow anymore (it's safe to do it without the module, isn't it?), but what's next? Find a wiring diagram and use a multimeter to check the resistance between the motor pins? I think I saw 4 pins per motor, so I'm not sure which to check, and the main question is what is the normal resistance (I can compare the 3 motors I guess)... Or just look for a used module on ebay anyway? I don't think I can check the module myself with just the multimeter, can I?
There was mechanical damage to the metal part that was holding the module, and its outer plastic box has a small surface scratch (somewhere below the big capacitor), but no sign of damage inside.
It's possible the Omron relays (the 5 white boxes) no longer switch on/off. Those may need to be replaced and you can check those first that if they are given a signal to turn on and off whether they do or not. Relays are tested for certain number of cycles, and that they remain in off state when they no longer can switch. It would be a safety hazard if it remained on and could cause the electronics to catch on fire. A couple youtube videos I found on the topic are below. I did not watch them but probably can help you.
It's possible the Omron relays (the 5 white boxes) no longer switch on/off.
Thanks. It is possible, but it's hard to tell how likely it is in the situation I'm describing: a seat moving forward, meeting an obstacle and frying something permanently so it blows fuses. I'm not sure a relay would die first, but I can't rule it out either.
Thanks. It is possible, but it's hard to tell how likely it is in the situation I'm describing: a seat moving forward, meeting an obstacle and frying something permanently so it blows fuses. I'm not sure a relay would die first, but I can't rule it out either.
you're showing the "components side": I inspected it visually: looks mint!
Can we see the "solder side" in particular all the relays solders.
Next you will interact with this module using your scanner to activate motors using scanner tests. The relays are protected electrically.
you're showing the "components side": I inspected it visually: looks mint!
Can we see the "solder side" in particular all the relays solders.
Next you will interact with this module using your scanner to activate motors using scanner tests. The relays are protected electrically.
Thanks,
I'm not seeing anything bad on the solder side either (although I may need magnifying glass to be 100% sure). It's not easy to make photos, I'll perhaps try again in the daylight, please let me know if you see anything suspicious so I can take a closer look and zoom in better. There is some whitish residue/coating on the sides around the pins contacts (visible on the photos), but I'm not sure it can cause short circuit. I could wipe it with alcohol, re-plug the module and the battery and try inserting a new fuse, but I doubt it'll help (and doubt it could appear as the result of the seat being stuck).
I don't have a scanner unfortunately, but can you please explain which type of scanner you are referring to? Will I need to plug the module back in for using it?
I'm not seeing anything bad on the solder side either (although I may need magnifying glass to be 100% sure). It's not easy to make photos, I'll perhaps try again in the daylight, please let me know if you see anything suspicious so I can take a closer look and zoom in better. There is some whitish residue/coating on the sides around the pins contacts (visible on the photos), but I'm not sure it can cause short circuit. I could wipe it with alcohol, re-plug the module and the battery and try inserting a new fuse, but I doubt it'll help (and doubt it could appear as the result of the seat being stuck).
I don't have a scanner unfortunately, but can you please explain which type of scanner you are referring to? Will I need to plug the module back in for using it?
With this round of pics you have good chances your module is ok.
The scannet that we like to use is available overnight on AMAZN ~130:
Search this string "LAUNCH CREADER MB ELITE"
it produces comprehensive pdf reports
and can interact with modules directly such as yest fwd/rwd.
With this round of pics you have good chances your module is ok.
The scannet that we like to use is available overnight on AMAZN ~130:
Search this string "LAUNCH CREADER MB ELITE"
it produces comprehensive pdf reports
and can interact with modules directly such as yest fwd/rwd.
So I plug the module back in and try a new fuse? If it blows again, will the scanner be able to check the module?
And I'm seeing Elite and Elite 2.0, is there any difference?
So I plug the module back in and try a new fuse? If it blows again, will the scanner be able to check the module?
And I'm seeing Elite and Elite 2.0, is there any difference?
your chair rail has likely gone sideways causing high motor current
Module has 4 + 1 connectors, right?
For testing don't plug back all the power connectors ... it will eat its next fuse, guaranteed.
I don't know which connectors drive which gear-motors
your chair rail has likely gone sideways causing high motor current
Module has 4 + 1 connectors, right?
For testing don't plug back all the power connectors ... it will eat its next fuse, guaranteed.
I don't know which connectors drive which gear-motors
LAUNCH SCAN: 2.0 sound better than 1.0
I disconnected 1 connector on the front and 3 on the back, and from what I'm seeing on the wiring diagram, there's one connector to 3 motors: front/back position, cushion recline and seat height, then another connector for back recline and headrest motors. So it may be a good test to connect 3 others except for the first one, connect the battery and insert the fuse. If the fuse doesn't die, then it's one of the motors, isn't it?
Okay, I plugged 3 connectors except the one that I think goes to the front/back, cushion recline and seat height motors, inserted a fuse - and got a nice video of a spark (even with sound). Disconnected the battery, removed all connectors from the module, inserted a fuse - and it was okay. Time to check the relays it seems. Can I check them without desoldering?
Okay, I plugged 3 connectors except the one that I think goes to the front/back, cushion recline and seat height motors, inserted a fuse - and got a nice video of a spark (even with sound). Disconnected the battery, removed all connectors from the module, inserted a fuse - and it was okay. Time to check the relays it seems. Can I check them without desoldering?
you're making progress!
Good thing you have the schematic
Your testing shows your module is ok while motors are not connected.
One motor is shorted out and frying fuses
There's nothing wrong with module relays.... they can not short +12 to GND.
Take 5mn to compare your seat motors:
use ohmmeter on the seat side of connectors
first motor = Ohms
second motor = ""
third motor = ""
With these Ohms values... guess which motor is bad?
(chair fwd/rwd ??)
Last edited by CaliBenzDriver; Aug 22, 2025 at 05:25 PM.
you're making progress!
Good thing you have the schematic
Your testing shows your module is ok while motors are not connected.
One motor is shorted out and frying fuses
There's nothing wrong with module relays.... they can not short +12 to GND.
Take 5mn to compare your seat motors:
use ohmmeter on the seat side of connectors
first motor = Ohms
second motor = ""
third motor = ""
With these Ohms values... guess which motor is bad?
(chair fwd/rwd ??)
Can you explain why you think the module is okay? I connected it without connecting to the motors, and still got a blown fuse... (sorry if I didn't phrase it clearly enough ). To me it looks like the module is not okay, but possibly not just the motor... I still need to check it without the seat recline or headrest motor connectors just in case.
Btw, should I disconnect the battery every time I plug/unplug connectors to the module? I placed it on the floor in front of the seat temporarily, so there's much smaller risk of affecting anything else around like airbag connections. But it it's safer this way, I'll keep doing it.
I did check the resistance on the motors before that though, and here's when it's get stranger... On the driver's side all 3 motors are within 1-2 ohms, but on the passenger's side it's only the seat height motor that's within 1-2 ohms, but both front/back and cushion recline are waay more, around 50 and 37 respectively. Which is something I don't understand. I'd expect faulty motors to have lower resistance, not higher.
Okay, I plugged 3 connectors except the one that I think goes to the front/back, cushion recline and seat height motors, inserted a fuse - and got a nice video of a spark (even with sound). Disconnected the battery, removed all connectors from the module, inserted a fuse - and it was okay. Time to check the relays it seems. Can I check them without desoldering?
From that... I understood fuse blows with 3 connectors plugged in. One of which connector must include a shorted circuit.
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