Troubleshooting Volvo seat switch issues.
The power seat system incorporates an On-Board Diagnostic subsystem used for fault tracing and repair. Diagnostic Trouble Mode (DTM) 1 is used to read stored fault codes. DTM 4 is used to calibrate the seat if control modules, motors, potentiometers, drive cables or other components are removed. The OBD systems vary by model and model year: in 740 and many 940 cars, they require a cable connection between the seat connector and the OBD Diagnostic Link Connector (DLC) box in the engine compartment above the left wheel well. 960 and 1994-95 940 cars can read the codes directly by inserting the OBD selector pigtail into DLC box “B” position 6. Press the buttonin box “A” once to select DTM 1 and read out the codes. Erase codes by pressing the button for at least five seconds, wait until the LEDs light up, then press again for at least five seconds. After releasing the button, press it again to obtain code 1-1-1, indicating codes have been erased. If you have a problem requiring use of the OBD system, buy the Volvo OEM Service Manual TP 8501201 Power Seat for complete diagnostic and repair information
MVS Forum Member rwaltco asks:
The drivers’ side power seat on my 97 850 doesn’t raise and lower at the rear of the seat only the front. All other directions are fine. How can I tell if it is the motor or the switch?
MVS Forum Member bobsnow100 replied:
I would first check to make sure nothing un plugged under the seat.
If everything is still connected than either get a test light with a probe or a volt meter to test power at the motor. If there is power at the seat motor than thats the problem. Make sure you’re pushing the seat button switch as your testing . If you’re not holding the switch electricity will not flow through. If there is NO power than check for power going into the switch. If there is power at the switch ,probe the other wire coming out ot the switch going to the motor and see if you get a reading.
I am not sure if the seat motors are all on the same fuse either. Might want to check your fuses
MVS Forum Member ferrari9 added:
I have the same exact problem with my 95 850. Everything works except the height adj at the rear of seat cushion. I retrieved DTCs that the wires to motors 1 & 3 are unplugged (which confused me a bit more since motor 1 is functioning as it should). I studied all the related documents provided in the service manual and by MadeInJapan about the seat components, wires, motors, etc. Upon examining the whole setup, I found that nothing seems to be unplugged.
When I press the switch I can hear the motor running inside the seat. Does this happen with your switch?
I’ve already spent enough money at the dealer trying to fix the entire seat (long story…). I’m going to have to take the seat out and really test everything. Sorry I don’t have any other info at the moment but I’m very determined to fix this so hopefully I’ll have some answers sometime soon. In the meantime, I’d suggest downloading the ’95 850 Service Manual’ (located at the very top of the 850 forum) which will have info pertinent to your model as well. There is alot of info in there about the power memory seats and I’m sure your’s is pretty much the same deal as the 95s.