RNEG mostly no fix

[CShape]

Hello,
i've got mixed results with RNEG satellites lately (e.g. since october 2023).

Most of the time i get 0, 1, or 2 Satellites, which results in no fix.

If the unit finds 3, aka gets a fix, it finds 9+ satellites then.
This is with a external FAKRA antenna, in fact i have 2 of them, same behaviour.

When i get 0 satellites, the gps time is utterly wrong(e.g. 12:35 when real time is 19:12), which can be seen in hidden navigation info menu accessible by setup + 1 + 2 + 3.
This does not mean the date, which is wrong of course due to week rollover anyway (pretending today is the 1st June of 2004).

So .... is the unit unable to use certain gps satellites, and if it really gets a fix it accepts all satellites from the constructed almanac then?

Also upon powering off and immediately powering on again, it doesnt get a fix anymore, except looooong driving & some luck .... almanac considered invalid i suppose.

Further ideas for this badly designed unit:
- it might invalidate almanac upon reboot, as GPS date due to week rollover is currently at 2004, which is WAY older then manually set date (2024)
- time for ephemerides building (around 40s) + almanac building (12 minutes)
- almanac is generally considered outdated for gps if older than 180 days
- so one would need to set the "week rollovered date" of the last cycle, e.g. 2004 ish
- trying to verify this thesis is currently impossible as the unit can not be set to a date below 2006-01-01

Unpacking the QNX firmware files i could not spontanously find where the date offset is added to GPS Week counted seconds.
But i suppose it must exist, since GPS dont transmit a date, so the date displayed from gps must somewhat be composed of a startdate + gps seconds.

Is there any alternative on aftermarket devices, which are fully operational (bc, wheel buttons, messages, configuration of car settings) on a C4 (excluding RNEG2 / RT6)?



... thanks for reading, that quite long post

Maybe someone has some good ideas to offer

[CShape]

New Results, setting a Date of now-1024 Weeks, e.g. 2004-07-08 yields better chances of getting a sat fix.
If using current date, rneg sometimes "connects" to a satellite which sends wrong datetime, something 2001-ish which will never yield a connected satellite.
Strange enough, this does not correct itself if it happens. Normally wrong Date/Time fixes itself after some minutes.
I don't think the unit is faulty, it think it has severe software problems.

But anyway, is there any RNEG user out here, where it still works without problems?
TIA

[GiveMeABreak]

This probably isn't the place for delving into the intricacies of GPS and the software, as Harman Becker who made this unit and the premium Navidrive 3D system at the time don't release any details of the system internals except to authorised service centres.

We do know that the MyWay system was (at the time of the N Week Rollover Bug) the only PSA system in use then that suffered from this bug. The solution was to set the year manually and more importantly untick the 'Synchronise with GPS' option for this to work.

However I can tell you that it is compulsory to go for a drive of at least 5 km in order for the GPS module to get a lock.
If you want to see what the system shows, press and hold the button "SETUP", then Select GPS coverage when the special menu appears. This will provide some info as to satellite locks.

[CShape]

Hi,
The point is that it often gets no lock on a 1hour drive, only 1 or 2 satellites - GPS Time of course deactivated.
Even having no lock, as long as one is on roads known in the map works unexpectedly good.
Having no lock and going a few km outside of known roads messes up the position totally.

Other time it finds 8 satellites, so i suppose it must be a software problem.

So this unit is not really usable anymore, i wonder if others having the same strange problems?
Would be nice if any owner could tell if it works for them or not with the same behaviour.

[GiveMeABreak]

The only thing I can add, is that the internal GPS tuner may be on the way out, so if this is consistent behaviour and you're sure the aerial is not at fault, it may be the unit itself. Officially, if the GPS tests were done (swapping with a test GPS aerial) and going for a drive with no change, then Citroen would advise the dealership to replace the Head Unit.

[CShape]

you're sure the aerial is not at fault

Yup, tried multiple fakra antennas .... same behaviour.

Today a drive for 35 minutes - only 2 satellites. Stop for around 2 hours. Another drive for 35 minutes .... jumped from 2 to 3 to 5 satellites in the last 3 minutes.

It feels like the unit only accepts certain satellites - and the 3rd enables something to accept more.
Probably the 3rd came into view just over the horizon or sth. like that.

If only i knew another RNEG user, which either have no problems at all or having similar problems ....

Buying a new/used RNEG is like using 100 € notes to light up a cigar - waste of money.
If only we had real alternatives from the retail market, where driving wheel buttons and car computer would work with.

Thanks

[GiveMeABreak]

These were not the best units Citroen chose to use unfortunately, but at some point they all start to go faulty like the RT6, suffering from flash memory failure. But the GPS tuner may be the issue if it is having problems locking on.

[Danilov]

you're sure the aerial is not at fault

Yup, tried multiple fakra antennas .... same behaviour.

Today a drive for 35 minutes - only 2 satellites. Stop for around 2 hours. Another drive for 35 minutes .... jumped from 2 to 3 to 5 satellites in the last 3 minutes.

It feels like the unit only accepts certain satellites - and the 3rd enables something to accept more.
Probably the 3rd came into view just over the horizon or sth. like that.

If only i knew another RNEG user, which either have no problems at all or having similar problems ....

Buying a new/used RNEG is like using 100 € notes to light up a cigar - waste of money.
If only we had real alternatives from the retail market, where driving wheel buttons and car computer would work with.

Thanks

Hi there, did you find a solution to your problem yet?

[CShape]

More or less i did. Or it is coincidence.
Setting the Date to the GPS time as seen by the uni t, so today something 2004-08-xx ish.
Fix is now obtained quickly.
But that was no immediate effect, it took some weeks. Of course satellite positions are now different than a few weeks back.
It could depend on some internal Date range too, which is now passed, e.g. for the unit we are now slowly approaching the range when those units were released/created.

Bottom line it works now for unknown reasons, only changed date to gps date shown in hidden menu --> navigation --> info.