Electrics: Parasitic drain question

[DaveFox]

2009 XC90 diesel. I have a parasitic drain, 2 brand new Bosch batteries in 6 months, the battery goes flat and unable to turn over after 3- 4 days from a full charge. I’ve had 2 professionals look at it with 2 different reasons and solutions but I still have the problem. With a meter to show amp drain, it shows -1.2, if I remove fuse 2 ABS from the under bonnet fusebox it drops to -0.80. I have a warning light ‘Anti-skid service required’ on the dash, if this is reset using a fault diag box the discharge then drops to 0.03 to 0.06, the next time the car is started / run the 'anti-skid warning is back and the drain then shows -1.2 to -1.4. I’m aware of the alarm siren battery fault but this has been checked and appears to be OK, can anyone offer some suggestions or advice?

[SwissXC90]

Isolate drain by pulling fuses and measuring, remembering that each measurement takes 20 minutes per fuse, as you have to wait for the car to fully go to sleep (doors closed and locked) before you can do the measurement.

You need to keep a written log:

Fuse Number | Pulled At (time) | Measured At (time) | Measurement
Example:
10 | 10:00 | 10:20 | -1.2 A

So with 20 fuses, this can take 400 minutes , which is 6.6 hours.

As you can see, this is a long laborious task that takes the whole day, maybe two days.

But maybe less if you have some prime suspects at the beginning.

Once you have confirmed the suspect circuit, use the Wiring Diagram and identify all devices using power on that circuit.

Repeat, this time unplugging the modules once by one until you find the definitive module causing the problem.

Once you know the module, use VIDA and check all parameters and fault codes of the affected module. The module may or may not be faulty: if it is not going to sleep it may be because one of it's inputs is incorrect.

As you can see, this is a long, tedious task.
You'll only achieve success through meticulous record keeping - at best on paper.

[DaveFox]

Appreciate the detailed reply, nothing better to do this weekend.....thanks again.

[cheshired5]

To save many hours of time, leave every fuse in place and probe the two exposed fuse contacts with a multimeter set to the lowest DC volts setting.
You're basically doing a voltage drop test across the fuse and a 0.000 reading means there's no current flowing through that fuse so it can be eliminated.

If you get a reading, there is current through that fuse but still leave it in place for now and make a note of the fuse.

Test every available fuse this way and you'll be left with a much easier to manage 4 or 5 active fuses/circuits by the end and you can see the impact of their removal on the current drain.

Don't discount the alternator diodes either. If you have a failure there, you'll have a drain which won't be spotted by any amount of fuse checking or pulling.