Brakes: List of DTC's to work through....

[currymunster]

Originally Posted by SwissXC90

It is extremely unlikely that you have multiple bus failures at the same time in different places in the vehicle.

The common point for all the CAN buses is the CEM.

If all those comms messages continuously come back, then you need to remove and inspect the CEM for water damage and corrosion on the connectors.

Don't bother with any other faults until you fix the bad comms problems.

Thanks, this is my job for tomorrow. One question I do have is where would the water be coming in from?
I'd rather cure the symptom AND the cause.

[gmonag]

The usual suspects are:
The AC evaporator drain (inside the car)
The scuttle drains (blocked with leaf litter)
Sunroof drain (blocked inside the A Pillar)

plus any number of other entry points for water.

[currymunster]

Originally Posted by gmonag

The usual suspects are:
The AC evaporator drain (inside the car)
The scuttle drains (blocked with leaf litter)
Sunroof drain (blocked inside the A Pillar)

plus any number of other entry points for water.

Rain stopped play so I'll hopefully be out there tomorrow.
This car doesn't have a sunroof so I'll check the other two.
It had not been well looked after for the last 3 or 4 years so I guess thinks blocked up will be inevitable....
Cheers

[currymunster]

Hi,
I've now removed the CEM and checked out. Can't see any water damage on any of the plugs, wires or outer unit and relays.
Removed the centre CEM bit and took off the both covers and the circuit looks perfect with no signs of water damage.
So with that in mind I went ahead and changed the brake pressure sensor(number 2)
The anti skid message has now gone off...yippee!!
Connected VIDA and reread codes and now I'm getting different codes each time I re read. On one occasion it wouldn't connect and said check ignition is on pos 2. If it is(it was) the suspect faulty CEM.
I turned everything off and now it connects okay.
But I keep getting codes that don't read true plus communication errors.
Apparently the mirror motors don't work(they do)
The rear cargo lights don't work(they do)
Rear brake lights don't work(they do)
You get the picture.
Big question now........
It's there a definitive way to diagnose the CEM so I don't waste money on a repair or replacement.
Thanks

[currymunster]

I've spoke to Volvo diagnostics yesterday and he said that the pre 54 plate cem's don't suffer from the water damage. Only in hot weather it can cause the relays to misbehave.
Due to this he said that a lot of the codes can be ignored, it's just VIDA being sensitive.
As regards the communication faults he said to susppect the individual moduals. IE, the DEM, BCM and UEM.
But seems everything is working as it should just ignore them for now.
Thoughts?

[NMB]

Originally Posted by currymunster

Hi, parts turned up and the parking brake is working fine. Surprisingly easy to adjust..
New battery fitted and codes deleted.
Took it for a spin and the read the codes.
Here's what VIDA spat out at me below.
Obviously the brake pressure sensor needs doing and I assume that is the reason for the anti skid service message.
I already have the part. It turned up today.
The next one is the brake pedal position sensor.
What I really don't understand is all the "Faulty communication"
How do I go about fixing those?

As a question, do you have a standard stereo on the car and is that working correctly?

[SwissXC90]

Always ensure your battery is good, or fit a 10A battery charger when doing any diagnostics with the engine off. Even with a perfect battery, you’l only get maybe 30min diagnostic time with engine off and key on before a low battery voltage warning comes up.

So keep engine running, or connect a charger, then clear codes and see what returns.

Many modules report erroneous errors when the battery voltage drops down too low, which can happen easily if diagnosing with key on and engine off and no battery charger connected.

[currymunster]

Originally Posted by currymunster

I've spoke to Volvo diagnostics yesterday and he said that the pre 54 plate cem's don't suffer from the water damage. Only in hot weather it can cause the relays to misbehave.
Due to this he said that a lot of the codes can be ignored, it's just VIDA being sensitive.
As regards the communication faults he said to susppect the individual moduals. IE, the DEM, BCM and UEM.
But seems everything is working as it should just ignore them for now.
Thoughts?

As it happens it is the original standard stereo.
The radio works just fine but there was a code to say that the CD module wasn't working. I didn't treat it as I'm not interested in playing CD's.
I can test it if you think it would help?

[currymunster]

Originally Posted by SwissXC90

Always ensure your battery is good, or fit a 10A battery charger when doing any diagnostics with the engine off. Even with a perfect battery, you’l only get maybe 30min diagnostic time with engine off and key on before a low battery voltage warning comes up.

So keep engine running, or connect a charger, then clear codes and see what returns.

Many modules report erroneous errors when the battery voltage drops down too low, which can happen easily if diagnosing with key on and engine off and no battery charger connected.

It had a brand new battery just fitted but I do admit it did come up low battery once so I usually have the engine running.
I did hear or read though that you can't delete codes properly with the engine running?
I suppose the low battery could have affected the code read our but I can't remember which time in afraid......

[SwissXC90]

Originally Posted by currymunster

It had a brand new battery just fitted but I do admit it did come up low battery once so I usually have the engine running.
I did hear or read though that you can't delete codes properly with the engine running?
I suppose the low battery could have affected the code read our but I can't remember which time in afraid......

What codes you can delete where and under what state (key on/off, engine running or not) is totally dependent on what control unit you are working with.

Just be very aware that low battery voltage can play havoc, regardless of how new the battery is.

Always watch your battery voltage in VIDA. Don't trust results if VIDA is reporting less than around 11.8V.

On my car, I'll see VIDA running with 11.8V displayed, and I use my little 5A charger to help prolongate my diagnostic session (5A is not really enough, but every ampere helps) and I also turn off any accessories I don't need, such as interior lighting, radio, nav, climate control etc., to reduce the power consumption.

The car will easily consume 10A to 20A with key on and engine off and many accessories running, and that will deplete a battery down to the low voltage warning threshold quicker than you think!

I think Volvo require a 20A capable power supply to be connected to the vehicle to maintain stable voltage when diagnosing.
It gets really critical when re-flashing controls units - but that's not something you can normally do at home anyway.