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Can one of you guys help with seat calibration in a 940 please?

shoestring

shoestring

Well-known member
Joined
Jun 20, 2009
Location
Swampscott, 01907
Finished recovering the driver's seat in the 944 and on re-install, the track got wonky. Took it back out, squared up the rails, put it back in. It works, but as I suspected the control module doesn't know where it is, so it goes back about 2/3 of the way and then you have to bump the switch about 30 times to get it all the way rearward adjustment. I see references to seat calibration via the DLC, but no instructions on how to do it.

Thanks in advance, and Happy Easter to those of you celebrating.
 
The Volvo manual you want is either TP32015 1992-on 940/960 Power Seats with Memory or TP8501201 Power Seats. The 940 power seat control modules use diagnostic connector B, port 6 for OBD-I communication. The '94-'95 940s have that connection, but the '92-'93 940s may not, although there is some suggestion they could be connected. With the pigtail in port 6, if you can get the LED to light when you press and hold the button for a few moments then you can use diagnostic test mode (DTM) 4 to try resetting whatever calibration is getting in your way. In general, I would expect that disconnecting the battery for a few moments should reset the calibration, but may not reset the three seat position memories.

I rather thought these power seats were dumb. As long as the tracks are aligned and clear then the motor should take the seat back all the way until the thermistor trips and the motor stops, just like a power window. Bumping the switch will give another kick of the motor until the thermistor trips again. If multiple bumps of the switch allow the seat to move all the way back then there's likely too much resistance near the end of travel.

I'm thinking you may have a motor drive cabling problem. It's a well known problem area with 700 and 900 power seats. The ends of the drive cables need to be adequately seated into the gear cogs of both tracks. As the cables and cogs wear, the spline in the cable can shift and start disengaging from either the track gear or the motor shaft. If the motor is only driving one track then the thermistor will trip and the motor stop before end of full travel. A giveaway that this is happening is when the seat twists a bit when you switch from moving forward to back.

There's an easy and permanent fix for this that every 700/900 power seat owner should know. You can insert a small spacer at each end of the cable so the spline will remain centered and stay engaged at both ends. A 1/8" long piece of a suitably thick finishing nail can be used as a spacer inserted deep into each cable socket (use a magnet to withdraw the spacer if needed). If you want, you can properly calculate the length of the required spacers by measuring the depth of the sockets and subtracting the lengths of the exposed cable ends then divide by two, but 1/8" will almost always be enough to center the cable. Do both ends of both cables on both sides of the motor. It's usually just the track motor that has this problem.
 
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945T said:
The Volvo manual you want is either TP 32015 1992-on 940/960 Power Seats with Memory or TP8501201 Power Seats. The 940 power seat control modules use diagnostic connector B, port 6 for OBD-I communication. The '94-'95 940s have that connection, but the '92-'93 940s may not, although there is some suggestion they could be connected. With the pigtail in port 6, if you can get the LED to light when you press and hold the button for a few moments then you can use diagnostic test mode (DTM) 4 to try resetting whatever calibration is getting in your way. In general, I would expect that disconnecting the battery for a few moments should reset the calibration, but may not reset the three seat position memories.
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Thank you. This is about as far as I got. I think the seats without memory are dumb, but those with memory are not. I was kinda hoping that they calibrated like window regulators in an E46, but alas, no. I bought TP8501201 from OTP Publications but my licensing is all f'ed up and I haven't been able to access it. When I get it figured out, I'll post it here.

Side note: The OTP licensing and use of LockLizard is a little frustrating. Many years ago I had all the 240 catalogs and manuals from them on CD (or DVD or whatever it was) and it licensed me on the laptop I had at the time. Well, 15 years later and I don't have that laptop any more, and it appears that I'm not being allowed to access the new manual because I'm registered to a different device than the one I'm using. I'm working with their tech support to try to work through it but I'm annoyed. Honestly, I'm sure it's something I'm (not) doing correctly.
 
shoestring said:
I bought the greenbook for it and have the proper instructions. Haven't done it yet, but I have no reason to think it won't work.
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Mind sharing what the procedure was? I'm having a similar issue with my seat myself
Works till about 2/3, then have to bump the switch the rest of the way.

No idea if it ever worked before cause I got the car like this
 
Sharpie_Eastern said:
Mind sharing what the procedure was? I'm having a similar issue with my seat myself
Works till about 2/3, then have to bump the switch the rest of the way.
Click to expand...
For all 1992-on 940/960 years with memory power seats, the power seat calibration procedures can be found on the new (April/26) Lemon manuals website:
https://lemon-manuals.la/Volvo/
The following is an overview with current links to the various sections in the Lemon manuals:

For OBD-I ('92-'95), the calibration procedure is done at the diagnostic connector under the hood using Diagnostic Test Mode DTM-4. For OBD-II ('96-on) you use a scanner on the service port. On later 940 models, port 6 on the B connector has the power seat control module connected. On early models ('92 and early '93) you will need to run a test wire to connect the diagnostic test lead directly to the power seat control module in order to be able to use the button and LED. You can tell if port 6 is already connected either by looking in the socket or attempting to use the test lead in port 6 to see if the LED will light when you push the button on connector A.

On the Lemon website you need to use the LEMON database rather than the CHARM database. The CHARM database (AllData) has the Volvo TSB which describes how to use the diagnostic connector, but the calibration procedure refers you to the Volvo Service Manual. The LEMON database has the diagnostic connector procedure and the full calibration procedure, but doesn't have the Volvo TSB (which has a bit more information, so I'll reference it here).

For the Volvo procedure to get the power seat control module into Diagnostic Test Mode you can refer to this TSB which can be found online
TP 32015/1 (ENGLISH); 11/91; POWER SEAT WITH MEMORY FUNCTION
https://lemon-manuals.la/Volvo/1995...s/Body and Frame/Technical Service Bulletins/
Expand the TSB section and goto to Power Seat - Fault Tracing/Calibration then start with the Overview section to determine your model, year and power seat diagnostic connection method.

Verify that the power seat control module is now successfully in diagnostic mode by being able to retrieve the codes using Diagnostic Test Mode DTM-1 then do a reset to Erase any codes. Go to the Power Seat section in the LEMON manual, eg.
https://lemon-manuals.la/Volvo/1995...and Diagnosis/Body & Frame/Seats/Power Seats/
Expand the System Diagnosis section then start with the Retrieving Diagnostic Trouble Codes section for your particular year and model.

The final step is to get the power seat control module into Diagnostic Test Mode DTM-4 in order to do the motor calibration. It's a 5-step procedure with the last command storing the calibration in permanent memory. Go back to the Power Seat section in the LEMON manual then go to Programming then to Seat Calibration, eg.
https://lemon-manuals.la/Volvo/1995...ats/Power Seats/Programming/Seat Calibration/

The OBD-I commands are:
4-2-3 DTM-4 Enables Calibration (flashes 4-2-3 if successfully in DTM-4)
4-2-1 Seat To Forward Limit, Front Of Seat Cushion To Upper Limit (Motors 1 & 4)
4-3-2 Backrest Tilts Back To Limit, Rear Of Seat Cushion To Lower Limit (Motors 2 & 3)
4-2-2 Backrest Tilts Forward To Limit, Rear Of Seat Cushion To Upper Limit (Motors 2 & 3)
4-3-1 Seat To Rearward Limit, Front Of Seat Cushion To Lower Limit (Motors 1 & 4)
4-4-4 Store Calibration (flashes 1-1-1 if successfully stored)

Once you're done that should have your seat motors doing full travel in all directions without needing to bump the switches (provided the tracks are clear). You will now need to re-program the three seat memory buttons.

The OzVolvo archives has an 850 Power Seats Memory pdf file with a similar calibration procedure. It seems there may be a missing step in DTM-4 for certain models. There's a 4-4-x command that identifies the type of seat used (motor response). The default appears to be the 940 seats. The code for the 850 seats is 4-4-1. You enter that command as the first command after entering DTM-4 before doing the calibrations. If someone has a Volvo Power Seat Service Manual perhaps they can check to see if there are other 4-4-x seat codes and post them as a reply here.
 
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The above information looks to be correct. Make sure you're going line-by-line when you use it, DO NOT skip steps. On Cam's '93 940, the seat moves with key off but needs the jumper wire to access the seat control module, which is contrary to what the literature says regarding early/late 940.

Like anything, read it through first to get an understanding of what you're being asked to do. It's not the simplest procedure.

Also, thanks for the link to the LEMON manuals!
 
shoestring said:
On Cam's '93 940, the seat moves with key off but needs the jumper wire to access the seat control module, which is contrary to what the literature says regarding early/late 940.
Click to expand...
1993 was a crossover year for the power seat wiring harness depending on early or late production. The TSB indicates the production chassis numbers affected and which methods to use. There was also a separate Volvo TSB with a field modification at the fuse panel so the power seat control module has power when the igntion is off, as was done with the later 940 models.

The variations to be aware of with these memory power seat control modules:
1) Control module either does (later) or doesn't (early) have power with the ignition switch off (field upgradeable).
2) Control module is either connected to a diagnostic port (later) or not connected to a diagnostic port (early):
2a) If not on a diagnostic port, either has a test connector on a green wire at the power seat connector (later) or doesn't have a green wire on the connector (early).
2b) If on a diagnostic port, is either connected to OBD-I (early, w/DTC under the hood) or OBD-II (later, service port in the cabin).
3) Control module is either being used with 940/960 power seats (default) or with 850 power seats.

Thanks to MasterBlaster for steering us onto the newly released Lemon manuals website based on the AllData manuals. These are bootleg copies and no respectable for-profit shop should be using them.
 
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