Update: Testing in the process. A microprocessor that will control the relay shutdown itself. We are tuning inputs that will control reverse and correct switching on.

 

Hi, I am new member and have been reading your investigation with interest and some admiration at the level of detail. I have a 2004 S type diesel with exactly the same symptoms the headlamps and fog lamps flash at 30 minute intervals when the car is parked and locked with the subsequent battery drain, I am currently disconnecting the battery each night to avoid this. I would appreciate it if you could share what your final solution was to resolve the problem. It may save me a lot of time and headache.

 

Hello, John. After hours of searching in the cabling, there were still grounding problems on the front FEM module. The ground was not clean. And the problems still persisted. A new module has been designed that includes a programmable processor. This new brain has door sensors, key switches, central opening units to maintain comfort of use. After a preset time, it disconnects the main relay, which otherwise still wakes up FEM. This bypassed it and the car does not flash, the consumption is 0.05A and it works fully.I created "MEM" Midle electronic module :-))) the brain is used by ARDUINO, own program. I did not find a better solution. It's more complicated, but it's a solution Price of parts approx 20- 25$

I tried to find help from an official dealer. They basically no longer repair these old cars. Spare part - FEM is no longer produced and another must be from a completely identical car. Reprogramming is required - there is no guarantee that this will work. The price for this operation was extremely expensive for the dealer. In my car, I had to repair the front harness under the bumper. Many cables have changed. The problem may be in some neglected place and somewhere there may be oxidation of the cable that we missed. That is why I chose this variant and because it has a very small price, I consider it a success.


you basically have these options:
1) disassemble the front and check all cables leading under the bumper. This is necessary and basically every S-type will have a problem here over time. see pictures

2) if that doesn't help and the grounding is fine, may be defective FEM see above

3) if FEM cannot be solved, some non-system solution must be done. Manual disconnection of the battery - comfortable opening, lighting, etc. will not work, or work around it and add a smarter solution, see my solution

 

 

Nice fix! If you can do that, you should be able to run the SDD software on a Windows computer for more troubleshooting. It helped me a lot on my str. And your statements about the oxidation or corrosion on the connectors of the front harness is right on the money. I found I had to basically cut off the old connector from that front harness and wire in an aftermarket 12 or 16 pin connector (male and female sides) to repair the harness because all of the sockets and pins were green and not making good contact after the previous owner had removed the belly pan and the wheel well liner

 

What software and cable do you use?

 

im using the $80 monggose knockoff with v131.03. Just gotta make sure you have a STABLE clean power supply hoked up that keeps the voltage stable at 13.5v or you can get problems

 

Hi Only_one, thanks for sharing what is a really neat solution- unfortunately way beyond my technical expertise. I intend to get the front bumper of and take a look at the wiring and earth's, I had to do this a couple of year ago when the Aircon wasn't working correctly which turned out to be a broken wire. If I can't find the wiring issue I'll fit a battery brain unit. I was hoping that the link cable used on the pre facelift model might be a solution but now not so sure and I would like to avoid spending money on something which might not work. Thanks again

 

Cable bypass what was described for pre face cars it doesn't work in my 2005 Stype .