Dealing with static leaks seem to be a never ending battle with the aircraft I work on.

These are all "old and worn" 767's that have a traditional Air Data Computer's.

The ADC's have two inputs, Pitot (ram air pressure from the front opening of the pitot probe used for airspeed computation), and Static (static pressure taken from the side of the aircraft or directly from ports on the pitot probe body used for altitude computation).

There is a ton of metal tubing criss-crossing the front end of the aircraft that are used to feed these pressure signals to the Air Data's.

When a tube has a hole or (most often) a "T" or elbow fitting has a crack, cabin pressure enters the line and increases sensed pressure. If a pitot line is compromised, airspeed will read high. If it's a static line, the altimeter will read low.

Finding these leaks can be difficult. We disconnect the Air Data quick disconnects (which spring seals the line shut) and apply pressure into the lines. We then go around spraying lines with leak detector looking for bubbles.
  
     
     

Using airspeed at 400 knots out of the Pitot/Static test box provides about (what we were guessing was about 4 PSI differential).

We experimented on our last troubleshooting venture. I have a low pressure regulator (something like this ) that I cranked full open while connected to the test box at 400 knots.
  
     
     
  
We had a reading of around 3 PSI. This was not a scientific, but it did show we really didn't get that much pressure out of the box.

We tried the regulator on its own with compressor air and dialed it up to 8 PSI. We could have gone higher, but for our find, 8 PSI was enough.
  
   Care should be taken to not apply these higher pressures to sensors with internal mechanical bellows (Elevator Feel Computers being one), as a possible rupture could occur.
  
  
With newer aircraft..... all these lines go away. A combined Air Data and IRU unit called (of course) a ADIRU. The pitot and static ports will have a Air Data Module located near the port. This unit sends data (I'm guessing 429 data bus) to the ADIRU.
  
     

What you sent doesn't seem to fit in with your previous issue on the SGU.
It's talking about the Flight Mode Annunciators, but I understand where you're trying to go with this as a comparison to your original problem.

Your reference is talking about SSM in relation to a 429 bus. It is saying the identifier for parity is wrong..... just like your SGU fault.

You need to verify the jumpers on the SGU rack. One is broken or open. It could be a pin pushed back, a wire broken off the back of the pin, or a wire is broken or disconnected from the junction splice. These can be checked with a Ohm meter. Start pinning the rack to find out which pin doesn't have continuity to the rest of them in the group. YOU MUST HAVE A "ODD" NUMBER OF JUMPERS CONNECTED.
  
     
     
 

Wire shielding is used to protect signal wires. 429 data bus twisted pairs, sensor outputs, co-ax communication wires.....

Shielding keeps outside inductance from close proximity wires from interfering with those shielded signals.

Shielding is normally grounded one one/both ends. Induced inductance is routed to ground.

The use of shielding is strictly an engineering function. I know of no prohibited reasons. Shielded wires add weight to the aircraft, which would be the driving reason of whether to use it or not.

You’ve covered all the bases on the wiring checks.

Reading 429 data bus wires requires an adapter.

The RTX adapter was the cheapest I could find. It is a single channel “receive” only. Numerous manufacturers have their own software and adapters.
These usually have multiple transmit and receive channels. They’re not cheap. My RTX was about $800US.

429 data bus output going to three locations.

Do you have 429 reader?

I would see if one of the user units has a bad 429 receiver (which I've seen before) which is locking up the entire data bus.
Disconnect one to see if the other two come up. If not, hook the first one back up and try another. Try it again on the last unit.

Is either of those data bus wires shorted to shield or ground??

Do any displays show annunciation or range marks that would indicate the data "is" reaching the display, but not the actual weather? If that was the case then you would need to go back upstream to the antenna input.

It looks like you've got a jumper that tells the unit to send the output to EFIS, is that present?

What is PN342 IAPS???
 

I'm still trying to get the flow of this.

Is Nav Tuning from the Garmins or is there separate Nav Control Units?

If the Garmins are tuning, it looks like those tuning requests go to the DME Master Indicator (KDI-574) on pins 11, 12 and the J-Box on 70, 51. from there the J-Box feeds the request to the DME (KN-63)  on pins F, 6. The DME output goes back to the J-Box which feeds the Arinc Adapter (KDA-689) which outputs 429 data back to the GNS (I only see an output to the left unit).

If I'm correct, this still leads back to a tuning issue from the #2 (or right) GNS. I circled some wires to check on a previous post. The "RNAV REQUEST" signal from each Garmin looks to be the signal which tells the Master Indicator which side (GNS request)  to forward to the DME.

If those four wires (18, 19, 20, 22) check good from the #2 GNS..... the Master Indicator would be the most suspect unit.

Also, three of those wires are connected to each other via splices. To make sure one Garmin isn't loading them down, try each alone with the other GNS not in the system. In your case.... disconnect the #1 GNS to see if the #2 tunes and displays properly.

The upper right section of this print only shows one 429 Data Bus coming from the left GNS.

Is there one for the right? It might not even be setup to use the right. 

The unit I have is a single receiver only. They have others that include the transmit function.

Some other products of note:

www.mil-1553.com/429analyzer

www.altadt.com/product/nline-ua429-arinc-usb/

www.astronics.com/ portable-avionics-interfaces-for-usb

Although there are many more companies that have similar products.

Image of paused data from video above....
  
  

Live 429 data bus from the #2 (right) Air Data Computer. This particular output was picked up from the Thrust Management Computer rack plug.
  

  

Acceleration data (in the case of a 767) is not a data-bus signal. It looks to be a constant output for lateral, longitudinal, and vertical sent to the DFDAU.

Pitch, roll, yaw, vertical speed, and other flight related data "is" sent via 429 from the IRU's to the DFDAU.