Electrics: xc90 both satnav and CD intermittent.

[SwissXC90]

You need to start isolating the issues:

Firstly: I have lead you astray. A 2003 XC90 has no MOST fibre optic bus.
The MOST appeared in around 2006

Remember that the satnav screen is totally independent of the radio

The screen is controlled by a serial bus from the nav unit: it sends it a command to go up, and what input to use (RGB or composite NTSC)

So don't confuse the screen faults with the radio

The screen is motorised, and has some form of limit. Maybe the limit mechanism has failled and the screen thinks it has extended or retracted. A mechanical issue which should be easy to diagnose when you remove the screen.

The RGB nav signals appear immediately before the screen has extended. Use a 'scope and check if you have RGB video signals. If you do, the nav is fine and likely it is the motorised mechanism which has failled.



So lets apply some standard fault finding techniques to the radio:

When the radio fails, does the audio continue or cut out? If it continues, then the amplifier and speakers are unaffected

During the fault situation, can you alter the volume with the steering wheel volume controls? If so, the bus connections are working, the radio has power and it can change the volume. This proves a large amount of circuitry.

During the fault situation, can change channels with eg the preset buttons or the steering wheel controls? If so, the bus connections are working, the radio has power and it can receive stations

You may just have a display issue, which is isolated to the radio display.

NOTE THAT all audio components have serial numbers which are registered in the CEM. Thus if a new 'stolen' device is fitted, the serial numbers won't match and the security system may not allow the device to be used. That's the mechanism in the MOST bus cars, for your year I'm not sure what security method is used.

I don't know enough about the UK RSE system to comment on the RSE, sorry.

[john langrick]

Hi, and yet again thanks for your response.

Today all was working, but after a short drive and stop, when srarted again the same problem. I drove a short 30mins distance, stopped and when I started all OK.

I noted this morning I had stacked CDs into the CD player. I have now removed them and it has not failed since so far, will see. (Quick update, just started car this evening, no sat nav etc, radio fine, changes channel and vol on steering wheel fine).

The radio has always worked, plenty of volume. Channels can be switched on steering column and volume adjusted.

When the problem is apparent, the status line to the bottom of the radio display screen is blank. When all working, there are symbols which include a phone symbol and I am sure phone would work if it had a sim.

When sat rises, all is well with rear sensors, phone, CD player etc and all stay on. Another time I will start car and none of these items work.

This is why I was looking at something that was common to these 'peripherals' if I can call them that and was looking at something in common, like an earth.

I now have all wiring diagrams, including the 2003 supplement. This includes grounding points, but I am afraid none appear to be common.

You have helped me greatly in many ways, including stopping me purchasing a 2004 exec ICM which I may well have done. It appears, should it need replacement, I would need to check part number very carefully so again, big thanks for that!

One of the local indi volvo guys is going to have a look with Vida in the new year. He knows more than most about volvo electrics, I will see what he he thinks.

I know these are not major issues, I only use the car to go to boatyard and after 35 years can find my way there without sat nav, but I have been used to fixing things in my past career and this problem has been frustrating.

Thanks yet again

John l

[SwissXC90]

You contradict yourself:

Originally Posted by john langrick

The radio has always worked, plenty of volume. Channels can be switched on steering column and volume adjusted.

When sat rises, all is well with rear sensors, phone, CD player etc and all stay on. Another time I will start car and none of these items work.

PS: the wiring diagram show a MOST fiber bus in a 2005 XC90, I'm using the 2005 XC90 for my reference, as the 2003 and 2004 diagrams are corrupt.

It is important to clearly distinguish here what is working and what is not working.

Does the radio ALWAYS work? Meaning: do you ALWAYS have radio reception and sound, regardless of the state of the nav, regardless of the state of the radio LCD display?

If so, is the problem ONLY the fact that the LCD Display sometimes does not show information?
When the LCD is not displaying anything does the keypad still work? and the volume controls on the radio?
If audio always works and keypads always work, that possibly isolates the radio problem purely to a faulty LCD. Which is the classic fault noted on the VolvoDiagnostic website: Intermittent/faulty LCD displays.
But it does not explain the coincident nature of the nav screen power loss.

Lets diagnose further:
You state that the fault happens when the nav screen fails to rise.

The one item in common with nav and the stereo is the power feed.

Permanent Power 30+:
Fuses Passenger compartment 11C/20
In a 2005 XC90, fuse F9 (10A, permanent power) on the left-hand fuse block in the dash (maybe righthand on RHD cars) feeds the Multimedia display (nav screen) AND the Control module, CD player (CD changer) AND the Accessory wiring, infotainment EXT.D

Accessory Power:
The 2003 XC90 4/56 Central Electronic Module (CEM) also has a fuse 11C/20 (likely 10A) feeding a relay 2/159 CMI16 which switches the power to EXT.D on and off in accordance with the key and the EXT-D power source timer.

You MAY have a faulty relay with burnt/bad contacts
The CEM fuses are above the panel under the steering wheel (the one with the footwell light on it)

It looks like the relay is pluggable, try swapping the relay

Given the simultaeneous nature of the nav screen failing when the ICM fails, I would suspect the CEM relay FIRST.

Secondly, I would suspect the Fuses as having potentially failling contacts, dirty contacts. These are extremely easy to change, swap F9 with another 10A fuse, and swap F11C/20 with another 10A fuse, noting where the suspect fuse goes to in each case. Drive and observe for a few days


The gound connections for the 31/84 A-post, right-hand side are for:
3/111 Light Switch Module (LSM)
3/112 Climate Control Module (CCM)
3/254 Steering Wheel Module (SWM)
7/192 Water detection sensor
16/46 RTI Display (screen and nav DVD unit)
16/60 Phone Module (PHM)
16/94 Infotainment Control Module (ICM), XC90
16/105 Audio control module (AUD), XC90
16/106 CD player (MP2), XC90
16/107 MD player (MP1), XC90
17/13 Data link connector
54/112 Accessory wiring connector, XC90

If you had a ground issue here you'd have a multitude of issues with other systems such as CCM and SWM. I don't think it's a ground issue.

[john langrick]

Hi, this is great, I really think we are getting there. Will print and carry out your recommendations. As I may have mentioned, this car is new to me, sold my faithful old v70 as it had difficulty with rough road to boatyard. About all components for suspension changed over last few years.. Hopefully this old xc90 has more ground clearance.

Just to make it clear, the radio always works fine, steering wheel volume and channel change always work, never fail. The numeric buttons also always recalls stored frequencies.

I know when I start the car tomorrow, the sat nav will raise after a couple of seconds and symbols will appear at the lower line of the display. When I next stop the car, about 20 mins to boatyard, all still working. It never fails once started.

When I go to restart the car after a couple of hours, the radio etc and its controls always work fine, but nothing on status line, sat nav does not rise, no rear parking sensors and when I select options on display screen, the MD and CD are missing. None of the phone options do anything, all useless.

Immediately i purchased the car i noted in the centre tray, a couple of tarnished 10a fuses. I will clean these up (I have contact cleaner) and start swapping these out. Will also look for earthing point on A post, this is not obvious when I last looked but I guess near the fuse holder? I cannot see any diagram for exact location. We have a local Maplin Electronics so may well simply replace all fuses in any case.

I will then (if no resolution) also swap some of the relays around, like for like and see how it goes.this all looks very promising, good job I am retired so have time to work on this. I remember when I got my last v70 some six years ago, the warning light came on whenever breaking. Bulbs were fine, but always the warning light came on. That was the relay and easily sorted.

So thanks again for this invaluable help.

Cheers john l

[john langrick]

Hi, sorry if I confused the issue, but to clarfy. When I started the car this morning, all worked fine. Went a short drive and stopped car. (To buy fuses)
When I stared car again after 20 min the radio worked fine, but sat nav not rising, no reverse sensors no cd etc. No symbols on bottom line of the radio display. On the radio now, steering controls work, and buttons on radio also select channels.

I was out to buy a new set of fuses which will now fit.

I looked under the steering wheel where light is but cannot see any hatches for fuses CEM). I can see where they are supposed to be from my wiring diagrams and assume the whole panel needs to be removed... My next job.
Sorry for any confusion earlier
Cheers john l

[SwissXC90]

The CEM fuses are behind the panel, you must drop the panel to access the fuses

Torx drivers required

[john langrick]

Many thanks, I could see the module but not the fuses. I swapped two lower relays as easily accessible.

Radio worked but that is it, could not get the rest to operate during many starts. Took relay out for part no so can order a couple of new ones, put them back on the original position. Ignition on but not started engine...all worked, sat nav popped up.

Started engine and sat nav lowered itself but lower status line on display remained....

Powered off and on again, sat nav not raised, no status line.

Symptoms seem to have changed slightly, so have ordered 2x relays so will start swapping out.
The cem seems to have some sort of finger clip on the bottom, will see if I can remove tomorrow as light fading.

Fyi, I attach pics of when normal with icons displayed and when problem exists. Just in case my eyes are deceiving me.. But not sure if I downloaded correctly.

Incidentally, do you mean the fuses are behind the cem? I really do not wantvto move it unnecessarily.
Thanks again

[john langrick]

Not sure if pics loaded here..

[SwissXC90]

Check the power feed for the screen with a multimeter
In fact, connect a voltmeter to the EXT.D supply to the screen and monitor it.
Observe if the power fails when the screen refuses to rise.

For the radio system you don't have a total LCD failure, just the lower line of icons
I think that is an internal ICM fault, send it to the Volvo guy in London for repair

Regarding CEM fuses: maybe there are non on your age CEM. What year was it again?
My oldest wiring diagram is 2005
The supplementary diagram for 2003 contains someminfo but not so detailled

[john langrick]

The car is 2003, will still try relays when they arrive.

I really cannot be without the car while I send this unit off, so will just have to live with it if the relays make no difference.

My analysis was that the radio displays what is available at power on. It seems there is a genal 'query' sent to all modules and the result of this 'hanshake' is displayed on the status line and becomes 'available' in the select menu.

Incidentally, there is a fuse in the harness to the satnav unit under the seat. It has a 30a fuse in it and looks a bit after market. Will check this has power tmr.

In my Haynes manual it details the drivers side fuse positions and gives f9 as satnav. In my owners manual, the f9 position is vacant. I guess this older model of xc90 is a bit different.

I can see a very useful ground point for lots of modules but where is it? The reference is under 31/104 , 53/438 and is phone module -16/60A:1, ICM 16/1A:10, CD player 16/106:4, MD player 16/107/4.
Not sure how to interpret these or where they are.


Will keep looking, but perhaps just have to live with this problem.

Thanks again.

Cheers john l