Help with a Bosch SLDA head unit in a Suzuki Vitara

[Dormouse]

I have been struggling to get any useful info from any other forums so anything will be useful

cheers

[GiveMeABreak]

Without being familiar with this unit specifically, and noting the actions you have already taken, it leaves one area that may be the cause - the Head unit itself. Specifically, these have a GPS tuner / receiver built into them if they are like most other systems and if after driving round and testing with a cheapo GPS antenna there is no satellite pickup, then it's very likely an internal issue.

[Dormouse]

That is the conclusion Imack of VivaVitara came to from his experience at a Suzuli Main Dealership. It is mine too.
However, being the pig stubborn "person" that I am, I will attempt to repair it.
A silly question. If someone "acquired" the mapping SD card from the sat nav "live", could it corrupt the firmware/software. I don't see how, but computers don't like drives being removed without a proper shutdown. Might an upgrade to the latest firmware help? Is it worth a try before I progressively pummel the head unit with bigger hammers?
cheers

[Dormouse]

These are various shots over time of the device info.
You notice that all the phantoms say OK. When I disconnect the various aerials the phantoms show nothing so the head is recognising its connections.

the one above is the current firmware version - 2015 as far as I can establish. The latest firmware should be 1860 I believe not 0830

the one above is what I get most of the time. The screen responds to the steering wheel buttons when I use them (not photographed )

the one below is a screen grab of what the display should be

[Dormouse]

I may be on to something. There was a Tech Bulletin from Suzuki in 2017 about earlier models having incorrect GPS location. It was associated with a poor installation of the roof aerial at the factory where the roof aerial wires were pinched during installation.

with all the aerials disconnected

with the gps aerial reconnected and the engine running

with all aerials connected

[Dormouse]

Am I correct in assuming this sat nav uses the FM signal as well the GPS signal?

[GiveMeABreak]

No, GPS uses phase modulation, FM is Frequency Modulation. There are usually different aerial stalks and aerial base units depending on the type of Head unit and services provided.

Unlikely that a software update will fix this to be honest, but I can't advise on these systems.

[Dormouse]

Yes. Which makes the Suzuki TSB all the more unusual.

[Dormouse]

I am trying to get an answer as to why the roof installed aerial causes the interference that affects the GPS. Once I get any plausible information I will put it here. If anyone has any ideas why this occurs, pop them in here too.

[Paul-R]

Why do you think it causes interference? What tests have you done?

[Dormouse]

Imack ( Admin ) from VivaVitara said so and suggested I switch off my DashCam as well as these sometimes cause interference as well. It uses the words "interference" on page 1 of the Suzuki TSB above. It does not describe what kind of interference.

I fittted a replacement aerial this morning and immediately on start up it gave ubat voltage and a good FM signal. Still no satellites even after setting a journey and doing a ten minute journey. I repeated the trip with both the onboard GPS aerial connected as well as my campervan one. Exactly the same. So, some progress on ubat and aerial but none on satellite acquistion.

Switch on

Running state at the end

replacement aerial

[Dormouse]

I am now going to strip the old aerial and see if there is any damge to the wire connections to the pcb or damage to the sheilding in the cables. There was issues with hamfisted installation of the aerials which crushed/pinched the cables when the aerial was clamped in place or the cables were pulled to stretch to the wiring harness.

[Dormouse]

My guess, at the moment, for my issue is that the power to the aerial PCB has been compromised somehow, possibly to the screen side of the FM aerial, hence the lack of ubat voltage in settings or FM aerial strength originally when I started. Without a schematic or wiring diagram, I am fishing in the dark just now. None of the GPS forums have any information about this particular issue that I can find.

This is the type of article ( of the many, many ) I have trawled through to get ideas why the ubat ( operational supply ) voltage may be linked to GPS.

[Dormouse]

SWMBO thinks I am totally nuts! "Just use the maps on the phone" is her (pragmatic and logical ) suggestion.

Unfortunately I am not wired up like that.

[Dormouse]

I have taken the old aerial apart as carefully as I could and found two potential issues.

this is the other end of the FM aerial lead.

The power cable sheath is badly gouged and I am not convinced that I caused it and it may have been done when assembled at the factory.

The stub of the FM aerial sticking out of the board is not clean and freshly broken looking.
There is no obvious marks in the inner sleeve of the aerial co ax.

Just how this causes interference for the GPS in the Head Unit I can't understand