CEM electrical gremlins - please help!

[Green440wedge]

I posted a thread a short while back about ignition barrel / relay faults, a lot of folk read it but no answers...

I have since learned a little more but I am essentially stuck with Passenger and Cargo CEM problems which are present on cold start up but which are making the car undriveable, I am faced with taking it off the road.... I would appreciate some experienced advice....

These are the symptoms.

How the problem started:

Ignition key I : DIM fluttering on/off. Simultaneous relay clicking noises Cargo and Passenger CEMs Switch to II problem solved. It was likethis for maybe 3-4 months.

Then my voltage regulator/alternator blew about a month ago. Voltage spike, strange electrics behaviour, "electrical system service required", then the battery light came on. I changed the alternator and battery. I have 12.6V available on cold start up, 80AH battery, so that should be OK.

Since then on cold start up the flashing DIM display corresponded to flickering low beam. If I switched the sidelights on before starting and then turned the knob to O the low beam would come on as normal. Then after warm up all as normal. Except that there was no DIM display on ignition key I. If I turn key to II and back to I then the DIM stays on maybe 5 seconds and then goes out. The radio will stay on but with a dim display, but only after switching from II to I. It is OK on II.

Now the flashing lights problem has got worse. Whether the lights knob is on O,1 or sidelights the relays click away simultaneously in the boot and under the dash on cold start up. If the wipers or reverse lights are engaged, their operation is intermitant in tune with the relay clicking. The internal electronics lights (window buttons, dash lights) also flash. Also on turning onto II the heater controls do not turn on immediately, almost waiting for a relay to engage... The indicators have also seemed to stop working.

I changed the low beam relay on the Passenger CEM, it made no difference this morning. There is no corrosion or burning or any CEM sockets or contacts, neither the Cargo or Passenger CEMs. The low beam shunt looks like new, at 20 years old. This problem also seems to have triggered the SRS airbag service required message again....

I am inclined to think the cause could still be an ignition switch relay but where are these located??

I can see from a wiring diagram that the Cargo CEM has:

RMA1 Relay 15l feed, rear 2/52

and the Passenger CEM has

CMA2 x feed overload relay 2/30
CMA3 15-feed overload relay

What do these do? I wonder if these control power supply to the CEM boards?

I am hoping I just need to change a couple more relays.... but which ones? The shunts look OK, but how do you test them with a multimeter?

Has anyone else had this nightmare? I have recently changed the heater matrix, alternator, battery, radiator fan controller, but this electrical problem is proving more problematic.

Volvo charge a lot for a new CEM I have heard and VIDA needs to code them in? They just look like fuse boards to me....

Any experienced advice would be appreciated as I am faced with parking the old girl up indefinately....

V70 II T5 2.3, manual, SE, year 2000.

[ASt85]

Get the codes read using a VIDA and DiCE, only then can you narrow down the causes of all the faults listed above.

Whilst I rather suspect you may have a failing DIM, that opinion is based on supposition and the nature and type of faults you describe.

If you throw relays and other bits of kit at the symptoms, you will only waste money in the short term and may never resolve the underlying problem. It might be worth asking if a member close to you is able to read your car's codes....don't bother with generic OBDII readers - they cannot and will not identify many of the manufacturer codes that Volvo use in their CanBus systems.

[Willow place]

Would a Vida / Dice show the problem of the Remote fob etc ?

[ASt85]

Most fob problems relate to flat batteries in the fob, only those faults relating to the various modules provide codes.
If the central locking system is a faulty it doesn't show on the dash system but will provide readable codes via the OBDII port nb the central locking module fob signal receiver is located in the mirror housing in pre-facelift models. If the mirror unit is replaced with one from a breaker it will not work as it has to be coded to the vehicle - that type of module coding also applies to the the driver's door switch unit which must to be coded to the car too. You can swap or replace switches in an existing module which then doesn't have to be recoded as the switch themselves are not coded only the unit in which they are mounted.

However, if the alarm siren is faulty you will get a worded warning in the dash system.

[oragex]

I'm thinking maybe a faulty ground somewhere. There is a wire behind the top of the engine that gets bad. May also look at the grounds right by the upper sides of the engine bay (big bolts). Two power wires behind the engine bay fuse panel - the wires may crack inside the plastic jacket. Thin wire at the starter for corrosion (even if it's just the starter).

If you suspect ignition switch, you may verify the green connector to the antenna ring and make sure the antenna ring stays solidly in place. If you have access to a junkyard, may remove the ignition switch - it's the black piece attached at the end of the ignition barrel - this part is very tricky inside so don't try opening it on your car

[Green440wedge]

Thanks for your input, I have thought possible failing Dim and ground connection problems myself....

I tried to work out where the CEM grounds, is this in the engine bay? I can't see a ground wire above the pedals...

In looking down there I discovered the buckle connector under the driver seat was unseated, I have refitted that, the related fault codes have cancelled for that.

I managed to get a Vida diagnostic read out relating to CEM power faults. I think driving the car 40 miles with a broken alternator may have done this (break down mechanic fitted a fresh battery) but I had no choice...

Initial state:

Cem - 1a04 X - Power supply signal too low
Cem - 1a07 15 - power supply Signal too high
Cem - 1a08 50 - power supply Signal missing
Cem - 8a07 Relay low beam signal missing
Cem - 8f12 Cem beam adjustment signal too low

I deleted these off on Vida delivery, and delivery now says no faults. But the SRS airbag text in the Dim is present....? I have a fault code on intial state for child lock - is this related to Srs?

Cem - 8d0f Relay, child lock Signal too low.

The rear door child lock makes switch makes the Cem relay click but no longer activates the rear door locks....? Duff relay maybe?

On start up this morning I switched the parking lights on before cranking the engine to avoid the flashing low beam lights. Subsequently the windows, mirrors and wipers did not work. Turned off and back on, this time with the low beam on, and after a bit of relay clicking it all came to life.

So I am I looking at replacing Dim relays or is the Cem circuit board faulty? Whichever it is, I blame the failed alternator.

Experienced advice would be appreciated.

[ASt85]

Originally Posted by Green440wedge

But the SRS airbag text in the Dim is present....?

I have a fault code on intial state for child lock - is this related to Srs?

Cem - 8d0f Relay, child lock Signal too low. The rear door child lock makes switch makes the Cem relay click but no longer activates the rear door locks....? Duff relay maybe?

More likely the switches within the lock itself - they can be changed but it is quicker and easier to get a replacement door lock mechanism from a breaker or eBay etc- they don't need to be coded to the vehicle

Originally Posted by Green440wedge

On start up this morning I switched the parking lights on before cranking the engine to avoid the flashing low beam lights. Subsequently the windows, mirrors and wipers did not work. Turned off and back on, this time with the low beam on, and after a bit of relay clicking it all came to life.

So I am I looking at replacing Dim relays or is the Cem circuit board faulty? Whichever it is, I blame the failed alternator.

Experienced advice would be appreciated.

As oragex suggests, check the middle 4mm connection to the solenoid....it is the small spade connector that is located on the solenoid back panel -= these corrode and prevent full voltage supply to deactivate the ignition isolator - please see photo below.

Re the ongoing problems from a failed alternator - try a cold reset - lift rear door for a V70 - turn ignition off and remove key, wait 10 or 15 minutes or at least until the cargo area light goes off and then disconnect the battery removing both +ve and -ve leads, cross connect the two leads for a few seconds (this process dumps any stored/latent memory) - turn the light switch to dip beam/daytime running position, re-insert the key in the ignition turn to position II (prevents a voltage spike which could cause the airbags to deploy!!!!) fully re-connect the battery, ie red +ve first then the black -ve, the alarm may sound, ignore it for the time being. If the alarm is sounding, close the rear door and remove the ignition key, close and lock the driver's side door USING ONLY THE KEY then unlock USING ONLY THE KEY, the process disarms the alarm system.

That process will remove most of the codes apart from the SRS/SIPS warning which can be done with a number of Autel or Autel copy code readers or if you have access a Vida+DiCE unit

[Green440wedge]

Ok thanks I'll check out the engine bay earths.

Is the child lock system linked to the SRS airbag warning message?

[ASt85]

Originally Posted by Green440wedge

Ok thanks I'll check out the engine bay earths.

Is the child lock system linked to the SRS airbag warning message?

No - the child locks only relate to the on or off position of the switch in the door frame and canbus sensed via the locking module - I usually set them to the off position before disconnecting the battery - theoretically they will then reset to the default "off" position on reconnecting the battery.

[Green440wedge]

Well I've spent the last couple of hours removing and cleaning electrical contacts in the engine bay. The 6 earths, 3 on either wing side, the alternator main connection and starter solonoid main connection and spade connector. Little to report other losing some small tools down the front never to be seen again. No corrosion, I wire brushed or filed everything shiny new.

Did the cold test as you call it. Turned it off. Started it again. Clickerty click, clickerty click, badly flickering low beam, delay in tje windows coming to life, then it was ok.

I have now spotted a minor coolant leak from the radiator. I am starting to think the old girl is fubard, maybe big time....

What next?.....