1998 S90 Transmission and Speedometer problem.

[kbmusic]

My gut is telling me that it's probably the speedometer/circuit board at this point as well. I took the car on a 60-mile round trip today, and the symptoms remained consistent. I only made two new discoveries:

1. My trip odometer button reset trick was only 50% correct. Simply switching the ignition from position I to position II four times seems to reset the flashing arrow - no need to hold down the trip reset button like a fool.
2. The speedometer does come and go on its own. Sometimes it comes back to life several minutes after it has failed, without performing the "reset" procedure (though the transmission warning lights do continue flashing).

I have no problem pulling the dash trim off again to access the gauge cluster and circuit board, it wasn't such a chore the first time, and it should go even more smoothly the second time around. Like I've said before though, I'm no electronics expert, and I've only ever handled a soldering iron a handful of times with limited success, so this might possibly be a bit out of my league. Does anyone have access to diagrams and/or pictures pinpointing the problem circuits/components, or have a step-by-step on the troubleshooting/repair process? (I already have the wiring diagrams for the car, including the speedo cluster, but they're pretty daunting to me). I know that's probably asking a lot, and I truly appreciate the help that everyone has already provided. Incidentally, I can get a used replacement cluster for $50 or so, so maybe that's the way to go. I'm just a little nervous that whatever used part I get will have (or will soon develop) the same problem. I'll just make sure it's returnable I suppose . . .

[precopster]

Some descriptive text about the repair.

[kbmusic]

Hello again everyone,

I just wanted to drop by with an interim status update and a couple of questions. I ordered a replacement speedometer cluster on eBay - donor vehicle was a '98 S90 with approximately 150k miles. It is scheduled for delivery tomorrow and I'm planning on installing it tomorrow afternoon.

There are a few things I've been wondering for the past few days, mostly questions to which I was unable to find a definitive answer, or received contradictory information:

1.) Exactly which sensor is responsible for sending the vehicle speed to the speedometer, is it definitely the speed sensor in the differential?
2.) Is it absolutely certain that, if the sensor in the differential is malfunctioning, the ABS light on the dash would illuminate as well? (Yes, the bulb for the ABS warning light is working).
3.) How would one access the speed sensor in the differential in a '98 S90 with its independent rear suspension. From what I've read, on older Volvos it is readily accessible. However, under my car, it is virtually buried amongst the rear suspension components and I can't even fit my smallest hex wrench in there to unbolt it, let alone reach up to the connector to unplug it. The only thing I haven't tried yet is raising both back wheels high enough to let the suspension sag completely, and I'm wondering if that might open up a space large enough to work in.

Basically, I'm trying to figure out if there's anything I can work on today while I'm waiting on the new cluster. I've read in several places that the speed sensor in the differential is a common culprit in the 900 series cars (among others) so I wanted to rule it out 100% before I take apart the dash again tomorrow. I know the consensus so far is that it's probably the speedo cluster itself (which is why I've already ordered a replacement), I just wanted to think this through one more time before tomorrow. All thoughts and comments are appreciated as always!

[kbmusic]

Replaced the speedometer cluster today, and . . .

. . . everything works like a charm now.

Thanks to everyone for the advice and insight. I probably saved hundreds by diagnosing and repairing this myself with your help!

I'm sure I'll be back soon - next on the chopping block are new front struts and various bushings.

[precopster]

With speedo errors on this series of car no real diagnostics just likely guess work which paid off this time.

Glad it worked. Keep us informed of your plans. If we can help....

[NSWolf]

Ok, So I'm having similar issues right now and i find myself a bit silly responding to an issue that was 3 years ago and I happened to be on vacation at the time of your mishap, but I hope it helps those out there. I worked at volvo and owned 140, 240, 760T, S90 (current), with another s90, v70, S60 in the fam.

So there are speed sensors at the engine and transmission. Each send signal to their respective ctrl. modules. The TCM sends info to the ECU, and it sends info bk to transmission and etc for the mix of fuel and changing gears. The speed sensors also get a say for the ABS sys. I don't know how or care to again after looking at the wiring efficiencies these Volvo models had. Efficiency, carries the cost of a few headaches in diagnosing. Check and clean speed sensors. All.

Second and most importantly, after hot and cold days, hot and cold seasons, the ctrl modules expand and contract. Solder pts. inside at board become loose or break. there is also chip creep, (chips popping out their housing in the board) check the soldering pts. and the patterns of the board.

yes you can check with a meter and ohms but sometimes the fastest is to look at the boards, same w/ instrument clusters. Just $5-10 or Euros, and problem solved.
goodluck and best
NSW

[TerrDawg]

how about known issues for the AW 30-40 transmission? I have 3 98' S90's my favorite one, (the one running best) is having transmission shifting issues all the sudden, it actually seemed like a stall - like maybe fuel pump was considering going out but after a couple hiccups it continued on home no issues, this morning I get in a take off and hear a whining noise .. after the sun comes up I'll check fluid of course but thought I'd ask about known issues but mostly these cars have given little to no problems since 2011 and I've had an 850 wagon, a 960 wagon and these 3 sedans