Hi all,

My Speedo and trip Odo suddenly quit, with no erratic behavior before that.
There's an OBD code A2 3-3-1 No VSS (Vehicle speed sensor)

I see from the FAQ that the speedo sensor connector and wiring is one
failure point, with another being at the instrument cluster including a fuse.
A bad ignition switch could also do it.

When I pull the instrument cluster to look for a fault to the speedo,
I want to know how to lube/service a sluggish trip odo that has appeared to be
binding. Maybe a little MMO on the main shaft?

Is the VSS sensor connector a bullet style connector? If so I'll be ready to
replace the female pigtails and stuff with Pentrox-A before getting under there.
Assuming the sensor is OK and just a busted connector or wires.

Has anyone tried to back up onto ramps with a 940 wagon?

Comments ?, Bill

Dear B.B.,

Hope you're well and stay so. If you can raise your car's tail-end, you'll find one or both of the wires, that connect the speedometer to speed sensor mounted in the differential cover, have corroded away. The wires are exposed to under-car hazards: water, snow-melt chemicals, etc.

To separate the wiring harness connector from the sensor's bullet-format terminals, I'd saturate the sensor's terminals with a corrosion-dissolver, e.g., Deoxit. Then, using a needle-nose pliers, with tips bent at 45°, grip one of the the female wiring harness terminals and - going very gently - try to turn it. It may take several saturations - over a few days - for the corrosion-dissolver to weaken the corrosion bond, to the point where gentle rotation with the pliers will break the corrosion bond.

Once you've removed the failed wiring harness terminal connectors, you need a short section of wiring, with female wiring terminals. I'd splice that to the wiring harness, first having slid sections of heat-shrink tubing onto the wiring harness. I'd then solder the replacement section of wire to the harness, and then apply heat to the heat-shrink tubing. I'd then wrap butyl rubber tapd around the rapaired section, to exclude water, salt, etc.

Butyl rubber tape - usually available at home improvement stores or auto glass shops - is very sticky, does not harden with time, and when compressed forms a leak-proof shield.

Before emplacing the replaced wiring harness connector onto the speed sensor's connectors, I'd apply a thin coat of di-electric (bulb) grease, to inhibit corrosion. I'd then wrap the top of the speed sensor in butyl rubber tape, to keep out water, salt, etc.

As to backing onto ramps, I got rid of ramps years ago. I disliked the idea of having to accelerate to get the car to move up the incline, and then having to hit the brakes to allow the tires to settle into the ramps "wells". I use floor jacks and jack stands to raise the car. This is slow but very safe. I never go under a car raised only with a jack.

Hi Spook,

Thanks for the almost instant response.
I suppose that busted wires at the sensor is whats wrong, and you helped
me by indicating the sensor has male bullet pins.
I think I have some extra female bullet pigtails from Dave Barton that should
do the trick for the busted harness connector .
I Just went through a similar issue with rotted horn and and OBD port connectors. I use non insulated #18-22 CU butt connectors crimped and soldered and then shrink wrap. (Beware junky cheap Chinese butt connectors made out of Aluminum or Brass or who knows what?)

I've had good luck with the ramps, for changing oil and also for placing front jack stands. Starting jacking from the ramps is easier and quicker to set the jack stands. I do understand that the thought of driving over the top of
the ramps is creepy, but no problems so far.

That Butyl seal may be the same stuff as ham radio "Coax-seal" used to weatherproof connectors. I haven't seen the Butyl tape at Home Depot, where do they hide it?

What to do to about the binding trip Odometer?
Maybe a little MMO will free it up?

It looks like a monsoon for the next day or so.
I'll be able to tinker with the instrument cluster before getting under the car.

Best regards, Bill

Hi Bill,
I would agree with Spook . Ive had the connector fail as well as the wire itself
where it`s clamped down.
I learned the hard way to not reset the trip odometer .Once on a 240 and also on a 740 I reset it only to have it never record another mile.
Good luck buddy.

Steve

The two VSS wires snapped off clean at the two pole bullet connector at the top of the rear end differential. To remove the connector, first you need to
cut and remove a bare safety wire loop with a lead crimp similar to what they
use for security on electric meters. The connector came out easily but you
couldn't see the color coding of the wires. I found out by chance that you
can't hook up it up backwards. Easy to fix by spreading the two tabs at the
flat side of the connector at the harness end using your fingernails to open,
then swap the two wires and snap the lock shut.

Dave Barton sells the complete connector with pigtails here:
https://www.prancingmoose.com/blackvinyl.html#2polewithpigtails
or get the pigtails and re-use the old connector shell see here:
https://www.prancingmoose.com/blackvinyl.html#pigtailfemale
Checkout the amount of info/parts at Dave Bartons's websites to
rehab old connectors and wiring.

The 940 VSS connector wire colors are:
Pin 1 = Brown, Pin 2 = Green/White (VSS w ABS).

It's a good idea to have some spare pigtails,

I had two of these 2-pole connectors also used for the two washer pumps and a
4-pole connector for the RSR should that need changing. LOOK OUT for a bullet
connector pigtail falling apart! You will have an adventure connecting an RSR
to a dead female bullet connector. Amarin could vouch for crapped out bullet connectors and how they can rain on your parade.

Spook, I didn't have any trouble getting the female pins free from the VSS.
The guts of the connector were OK, the wires broke off clean with no chance to see the color coding.
I used Penetrox on the pins plus back filled the the top of the connector with Penetrox, then wrapped Coax seal and black tape over the harness to weatherproof.

Coax seal sounds similar to the Butyl tape you mentioned, it's putty like and never hardens, coming apart easily years later to service.
Coax-Seal #104 (5' X 1/2" roll) https://www.ebay.com/itm/226015162774

Backing up onto the ramps was easy, quick and safe. Able to do that job
without lugging jack stands. I was concerned that I'd rip off the muffler
but all went well.

There's a 5MM hex head cap screw if you have to remove the VSS.

The OEM VSS price was set by some F(ord)rankenstein beancounter on drugs.
Sourcing a new VSS was an adventure, there's some rear OBD/speed sensors at Aliexpress but their message system is kaput so I could not get fitment info.
Maybe they have one that works for $10-15?

Dave Stevens: Check out Aliexpress with their creepy search engine.
Search for "volvo sensor". and find a lot of interesting stuff,
maybe some of it works? get a new AMM for $10. :-)

It turns out my sensor is fine, I don't need a new VSS,
I'm as happy as a clam at high tide.

Happy motoring, Bill

Hi Bill. An excellent summary post to let us know how you made out and the proper fix. We're all so lucky being able to get these kinds of rare connectors from Dave Barton. And no way am I even going to experiment with a $10 AMM from China. I do have my limits!! ::))
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now