02 V70 Rear electrics failure

[tony209]

I've now lost all my rear electrics!
VIDA says;-

PDM -003E control module signal too high (everything controlled by this module works)

CEM -1A5A Communication with REM control module signal missing

Background history -

I have a dog that pants a lot when in the boot and thus in winter, the carpets are always damp. when the sun comes out, this creates condensation in the car - unless a window is cracked open. For a few years now, every time the condensation occurs, the rear tailgate and passenger door locks stop working. However, all that was required was a quick wipe of No.1 fuse or in worse cases, a few minutes of warm air from a hair dryer blown on to the REM sorted the problem.

Last year, the information center Kept intermittently displaying "Rear Tailgate Open", added to this, earlier this year, the rear locks stopped working but I wasn't able to fix the problem in the usual way. My car sailed through its MOT a couple of months ago and within a few days, the rear wash/wipe stopped working. A week or so later, the reversing lights stopped working and then a couple of days ago, the rear brake lights. What is working, are the indicators, rear lights and the fuel gauge (latter two are REM controlled)

I've checked the wiring around the tailgate hinge, they are in good condition with no breakages. I've never used a multi meter before so not 100% on how to use them but I have had a go and I have 11.2v (13.5v with engine running) at No.1 fuse (REM power supply) voltage readings at connections to all the relays but no voltage reading at any of the other fuses.

I'm leaning towards a failing REM circuit board but before I buy a replacement, can anyone suggest what to check with the multi test meter and how to use it!

[jasmith44]

see this. https://www.youtube.com/watch?v=TdUK6RPdIrA

[ASt85]

Before you start testing - it is worth pulling each relay from the REM and cleaning each of the male spade terminals on the relay with coarse cotton cloth and propyl alcohol (contact cleaner) or fine wet and dry/emery cloth and then replacing it, pull each one out and replace it several times before you move on to clean the next one.

Many of these faults come down to surface corrosion problems which prevent the circuits closing as they should. Dog "slobber"/saliva is acidic as is canine breath if they are in an anxious state which can kick of the corrosion!!

[tony209]

Originally Posted by jasmith44

see this. https://www.youtube.com/watch?v=TdUK6RPdIrA

A bit basic, I manage that much using the instruction that came with the multimeter but thanks for the help anyway. I was looking for pointers on what to check on the REM

[tony209]

Originally Posted by ASt85

Before you start testing - it is worth pulling each relay from the REM and cleaning each of the male spade terminals on the relay with coarse cotton cloth and propyl alcohol (contact cleaner) or fine wet and dry/emery cloth and then replacing it, pull each one out and replace it several times before you move on to clean the next one.

Many of these faults come down to surface corrosion problems which prevent the circuits closing as they should. Dog "slobber"/saliva is acidic as is canine breath if they are in an anxious state which can kick of the corrosion!!

Thanks for the reply. I've tried cleaning all the spades - fuses, relays and shunts. I suspect that you may be right on the corrosion but I think it may be the female connectors at fault.

I took the REM apart, the PCB is coated so shouldn't have been affected by corrosion but looking inside, the power(?) connectors look corroded.

[ASt85]

It might be worth running an emery board through/across the the female terminals - it is worth trying anything that gets rid of the surface corrosion on any of the contact points.

[tony209]

Brake lights are now working, it seems that I may have problems with several relays. The twin relay 9494782 that plugs into RMI5 (Brake lights) & RMI6(Rear fog lights) was faulty, although connecting a battery to the +/- terminals makes it click. I've read that this was a recall on some cars and replaced with 2 x 8651661. My car has only one of these, RMI4 (Reversing lights). Plugging this relay into both RMI5 & RMI6 doesn't work so I tried a 9441161- no joy. Tried a spare 9162300 in the RM15 brake socket and now I have working brake lights, this would suggest that the reversing light relay 8651661 is also faulty. I tried the working 9162300 in RMI6 and RMI4 but no joy. Looking at the wiring at the back of the REM, it would seem that some relays might pass on power to other relays and on my car at least, that twin relay might operate as a single unit as well as individually.

Just spoke to my local Volvo dealer parts department and 9494782 has been replaced by 8651661 and 30765041 - but they couldn't tell which way they fit! Also, 8651661(which also is used for the reversing lights) has to come from Sweeden!

[tony209]

Originally Posted by ASt85

It might be worth running an emery board through/across the the female terminals - it is worth trying anything that gets rid of the surface corrosion on any of the contact points.

All sorted, I picked up an identical REM from a local scrappy, tried swapping over all the relays and fuses first but no joy, changed the REM board- bingo! Everything works now, except that the tailgate still registers as being open when it is shut. There is a small micro switch in the lock, it seems OK but I can't get any readings from it. If I bridge the terminals, would that do the same job as the switch?

[ASt85]

Originally Posted by tony209

If I bridge the terminals, would that do the same job as the switch?

Yes, but then it would permanently register closed even if it was open - further I'm not sure the tailgate would open via the central locking and could well become permanently locked. If you are sure the switch in the lock is the problem why not get a complete lock from the same local scrappy and change the lock. There's no lock barrel to change. I think it is only the 7 seaters that are usually fitted with a combined manual/electric boot lock. If a boot/tailgate key lock is fitted, it is found next to the number plate lamp and not physically part of the tailgate lock mechanism i.e. it only acts on the switch in the lock itself.

[tony209]

Originally Posted by ASt85

Yes, but then it would permanently register closed even if it was open - further I'm not sure the tailgate would open via the central locking and could well become permanently locked. If you are sure the switch in the lock is the problem why not get a complete lock from the same local scrappy and change the lock. There's no lock barrel to change. I think it is only the 7 seaters that are usually fitted with a combined manual/electric boot lock. If a boot/tailgate key lock is fitted, it is found next to the number plate lamp and not physically part of the tailgate lock mechanism i.e. it only acts on the switch in the lock itself.

I was only intending to bridge the terminals as a test to see if the switch was at fault, before I buy a new lock - needlessly if the is a problem is with the wiring. I can't get a volt or omes reading from the switch or the two wire at the connector connector. The lock works fine only problems I can't lick the car with the alarm set and I have had to remove the interior cargo light.

If I connect the multimeter to two terminals in the connector socket that links to the micro switch, shouldn't I get some sort of reading?