Light warning ⚠ issue Topic is solved

Post by **firstv70volvo** » 15 Dec 2020, 13:28

ashleyg82v702001 wrote: ↑15 Dec 2020, 12:45 Oh OK, for the sake of £20 I might try it. I'll match the part numbers and have a lookski to see if it's like the door modules with a software code sticker.
that's how I did my PDM and it works a treat...

If you do pull out the REM center section in your car you can easily pry off the cover to see the top of the circuit board and components. See the attachment of the area I suspect where the problem is, it's the components related to the shunts, a couple of chips, transistors, resistors and capacitors. If you could take a look in the area for any obvious damage such as overheating it would be appreciated and maybe a photo too.

Volvo REM.pdf: (1.03 MiB) Downloaded 106 times

ashleyg82v702001 · Post by **ashleyg82v702001** » 15 Dec 2020, 13:36

Brilliant, thankyou probably be a few days before I get the time but I'll keep you posted

ashleyg82v702001 · Post by **ashleyg82v702001** » 17 Dec 2020, 05:18

No obvious issues, board does not show any obvious sign of burnt components or smell burnt.

Disconnected checked terminals, all look clean and undamaged, shunts tested and seem to be OK (no broken circuit)
I'm thinking now if there is a common wire for resistance comunication to the front of the car? Any ideas

? Could it be the rem working but unable to send the resistance signal to the front?

Post by **firstv70volvo** » 17 Dec 2020, 08:09

ashleyg82v702001 wrote: ↑17 Dec 2020, 05:18 No obvious issues, board does not show any obvious sign of burnt components or smell burnt.

DSC_1794.JPG

Disconnected checked terminals, all look clean and undamaged, shunts tested and seem to be OK (no broken circuit)
I'm thinking now if there is a common wire for resistance comunication to the front of the car? Any ideas ? Could it be the rem working but unable to send the resistance signal to the front?

Thanks for the photo of the board. The REM communicates through the CAN bus interface, there's no common wire for resistance to the front of the car. From what I can tell looking at the circuit board the voltage drop across the shunt resistors goes through some op-amps, which controls a transistor and this signal is sent to the micro controller. I assume the micro controller monitors the signal level sent from the transistors and determines from these signals the status of the current in the each of the light circuits monitored. That's at least 5 separate outputs from the transistors to the controller and I'm trying to think of what is in common with all this that would cause the problem. It's not easy to measure signal lines in the REM because everything has a conformal coating and the covering over the circuit board when in the car and how small everything is with this circuit board. It's not designed to be debugged or repaired easily and I'm always impressed with the work Xemodex is able to accomplish with these modules.

I still think the problem is with the REM itself but need to think of a way to confirm this for sure before sending if off for repair or replacing it.

ashleyg82v702001 · Post by **ashleyg82v702001** » 23 Dec 2020, 07:15

Oh yeah!, oh yeah!, oh yeah!..... All fixed £12 cost and hours of searching for a problem... It was a failed REM.
Got one from breakers for £12 plug and played.

This little box has a lot to answer for!

Post by **firstv70volvo** » 23 Dec 2020, 07:44

Nice work, you fixed it so inexpensively and without needing programming? How close of a match is the replacement, same year, model and part number?

Edit
I was working on getting back to you and was documenting how this bulb out circuit works based on looking at the circuit board. The REM I have was from a 2004 S60 I had picked up from a local salvage for the relays and shunt parts and it looks like the bulb out detect circuit is very similar but still different from the photo of your REM circuit board.

I was looking for something in common because every rear light monitored for a bulb out was giving you a warning. Take a look at the link below, it shows how there's individual circuits for each shunt and the voltage level from each of these circuits goes to a pin on the microcontroller. What I think may have happened is the microcontroller may have been damaged from an overvoltage condition. The bulb out circuit has a 12V input and I can see a possible condition where the shunt or a component on the circuit board is open and causing too much voltage to be sent to the microcontroller. Pure speculation but I'd like to ask a favor since you have the old REM laying around. If you have a meter can you measures for continuity between pins 5 and 1 on each the shunts (see the pinout in the link below). There should be near 0 ohms between 5 and 1, actually you should see this reading between every combination of the pins, you won't be able to measure the resistors values because they're so small in value. I'm looking to see if there is one shunt with an open between pin 5 and 1. Not likely since the problem can also be with the circuit board but worth a check.

This may all be too much detail since you've got your problem fixed but I used to do circuit repair work a long time ago and it's still of some interest to me how things fail. I noticed they made a design change where they added a resistor between bulb out circuit, which is an op-amp and a transistor that would better protect the microcontroller against too much voltage reaching it if another component had failed.

Here's a drawing of what I gathered about the bulb out circuits from looking at the REM main board

https://app.box.com/s/fk5knzzki9791x6cqjnsxn1pfz4kv9ig

ashleyg82v702001 · Post by **ashleyg82v702001** » 23 Dec 2020, 08:11

Same part number off of a 2.5turbo diesel v70 2000 so completely different engine about 6 months older in manufacturers date

Post by **firstv70volvo** » 23 Dec 2020, 08:40

ashleyg82v702001 wrote: ↑23 Dec 2020, 08:11 Same part number off of a 2.5turbo diesel v70 2000 so completely different engine about 6 months older in manufacturers date

Thanks, that's good to know.

Please see that I made an edit in the previous post and included a drawing of what I was working on about this problem and that I'd like to ask another favor of you if you have time and a meter. Just wanted to know if there was a problem with one of the shunts and if there was an open between two particular pins; 5 and 1. It's a long shot there's a problem with one of these hunts but worth a check.

ashleyg82v702001 · Post by **ashleyg82v702001** » 23 Dec 2020, 08:56

I'm using all my original shunts and relays as I only got the module...
Everything seems okay so it must have been a problem with the module board.
When I got the car it had a dead PDM it caused a flat battery within a few hours by randomly operating the passenger window whilst parked and switched off.

I'm thinking the REM may have got a surge upon jumping by my brother in law before I took ownership. He was jumping to the battery in the boot not the jump point under the bonnet. 1st module in the line would have been rear in that instance

Post by **firstv70volvo** » 23 Dec 2020, 09:32

ashleyg82v702001 wrote: ↑23 Dec 2020, 08:56 I'm using all my original shunts and relays as I only got the module...
Everything seems okay so it must have been a problem with the module board.
When I got the car it had a dead PDM it caused a flat battery within a few hours by randomly operating the passenger window whilst parked and switched off.

I'm thinking the REM may have got a surge upon jumping by my brother in law before I took ownership. He was jumping to the battery in the boot not the jump point under the bonnet. 1st module in the line would have been rear in that instance

Yup, the original shunts must be good. Jump starting a car can be a brutal environment for electronics that don't like big current/voltage spikes. So good to hear you got the REM problem fixed without spending a ton of money.

Light warning ⚠ issue Topic is solved

Re: Light warning ⚠ issue