snoman

do you happen to know what B41 connects to? looks like from the diagram that it may be connected to something near or similar? that's cool that B228 can be tapped for more uber cool stuff, (im still thumbing through my manual to find out the pinouts for B228s 10-pin connector to see what signals are running out of there..)

I'm out of town right now, but I'll take a look later this week for B41.

There is a page in the Subaru tech manual dedicated to the "OP Connector" that shows a large diagram of this connector's pinouts.

I just installed an XM Navtraffic receiver. During this installation I discovered the "optional connector". This connector, B228 on the front bulkhead harness, is called the "OP Connector" in the Subaru tech manuals.

This connector is a one-stop shop for wiring a navigation system. It has a +12 V unswitched power lead (up to 7.5 A), vehicle speed signal, backup light signal, and about 10 other signals.

The connector is dangling underneath the steering column, not connected to anything. I'm guessing that Subaru's OEM navigation system uses this "Optional Connector". Either way, it's another option for locating and tapping these signals when installing aftermarket equipment.

I'm going to be anal here - Vehicle Speed Sensor.

 

(if anyone sees my OCD meds laying around let me know, can't find 'em anywhere...)

The whole point of this thread is that the Legacy does not have a conventional speed sensor, and the speed signal must be taken from the ABSCM instead.

update?

Well it seems to be working somewhat better with the speed signal attached. The navigation system now tracks my position through tunnels and in the downtown area between the skyscrapers.

I've been doing mostly highway driving, so the system hasn't completely learned left/right turns yet. Positioning should only continue to improve.

Incredible post! You really improved on my "green black wire" nugget to the nth degree. I bet your nav is a little more responsive now...

Well I did this last night and I've only driven 8 miles since. It's too soon to tell while it recalibrates. Hopefully there will be an improvement, because I was very disappointed with the accuracy of the AVIC-N2.

I did notice that the AVIC-N2 reports 50% confidence in distance after only 8 miles! Previously, without the speed signal it took over 1000 miles to reach this confidence level!

Does this have any effect on the ABS?

No. The ABSCM produces a rather strong waveform ranging from 0 to 5 volts. The navigation system's VSS input also has a high impedance, and shouldn't affect the operation of the ABS system as long as you tap the speed signal correctly. Your car will not know it is connected.

For simplicity, I would recommend using a "vampire tap". These plastic squeeze-type connectors are available at Radio Shack and allow you to obtain the signal on a wire without having to cut it!

http://rsk.imageg.net/graphics/product_images/pRS1C-2266845w345.jpg

I'm hoping to clear up the confusion regarding the Legacy's vehicle speed signal. Many aftermarket navigation systems require a connection to the vehicle's speed signal. While the Legacy lacks a conventional speed sensor, it does have a conventional speed signal.

The antilock brake control module (ABSCM) calculates the vehicle speed from the 4 ABS wheel sensors. The calculated vehicle speed is sent to the gauge cluster, or "combination meter" as a 0-5 volt pulse waveform. The ABSCM and gauge cluster are among the few locations where the vehicle speed signal can be tapped. This signal is not available at the ECU.

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I have found a very convenient location for tapping the vehicle speed signal. It is located inside the cabin so you don't even have to run a wire through the firewall!

The ABSCM in the engine compartment connects to the bulkhead harness (connector B301). The speed signal is passed from the "bulkhead harness" to the "instrument panel harness" underneath the glovebox at connector B38. The vehicle speed signal is carried on Pin 18 of connector B38. It is a green wire with a black stripe. See the wiring diagrams below.

http://users.adelphia.net/~ajhuba/vss/pic1.jpg

http://users.adelphia.net/~ajhuba/vss/pic2.jpg

Okay, that last diagram is a mess! I have included the following pictures to show where you can find the B38 connector.

First, you'll have to remove the plastic cover underneat the glovebox. It is held in place by 3 push-in fasteners.

http://users.adelphia.net/~ajhuba/vss/pic3.jpg

After you remove the panel underneath the glovebox, you can access the connector. You cannot see it unless you almost put your head on the floor of the car and look up. The connector is recessed behind the black plastic on the far right side.

I was unable to take a picture at such an extreme angle, so I disconnected the connector and lowered it some to depict its location under the glovebox.

http://users.adelphia.net/~ajhuba/vss/pic4.jpg

This shows the unplugged connector. All Subaru connectors are keyed and unique, so you can compare the shape to the pin diagrams above to confirm you have the correct one.

http://users.adelphia.net/~ajhuba/vss/pic5.jpg

If you are installing a navigation unit, I would highly recommend placing the computer/sensors inside the glovebox. It is literally a foot from the speed signal wire, and it's a central location for other audio connections.

http://users.adelphia.net/~ajhuba/vss/pic6.jpg

For those of you using a Pioneer AVIC-N2 navigation server, you can easily confirm that it is receiving a speed signal from the Legacy's ABSCM. On the navigation menu, choose "Settings", then "Hardware Info", and then "3D Calibration". If connected correctly, the "speed pulse" counter should increase while the car is moving. The learning status will also say "3D Hybrid" when a valid speed signal is detected. If your AVIC-N2 was already calibrated before connecting the speed signal, you will have to reset the "Learning Status" before it switches to 3D Hybrid mode.

http://users.adelphia.net/~ajhuba/vss/pic7.jpg