Fuse 11 (engine, SRS, etc) keeps blowing
 

Hi,

I'm looking for some help on this.

A few days ago fuse 11 in the cabin on my 2013 XC90 - a 7.5A - blew. I lost all ignition, dash, etc. A quick replacement and I was on my way again.

Fast forward 5 days, and it's happened again. However, the fuse keeps blowing this time as soon as I switch the ignition to 'I', even a 20A.

I've checked all the 12v sockets and they're clear of any rubbish. I also tried pulling all 6 relays under the bonnet but the fuse still pops as soon as I turn the car to the 'I' position. Next I tried pulling the fuse for the air-con, but the 7.5 fuse still keeps on popping.

Does anyone have any suggestion on where to start looking, or is this a job for an auto-electrician?

The car is a diesel. Thanks.

The 12v sockets are fused separately so unlikely to be related to those.
Unless you're familiar with car wiring and have a clamp-on DC ammeter with peak-hold, you'll probably need an auto-electrician.
A temporary workaround may be a re-settable 12v circuit breaker rated at 7.5A.

11 Ignition switch, SRS, engine control module, immobilizer, transmission control module

http://www.autogenius.info/volvo-xc9...e-box-diagram/

If the fuse is blowing immediately the ignition is turned to POS I then you have a short to ground

This is very good news, as it is easy to fault find

Let's apply some logic:
Fuse 11
Ignition switch, SRS, engine control module, immobilizer, transmission control module

Looking at the wiring diagram, F11 goes to the ignition switch and appears as Terminal X (pin 6) and then goes to these devices:
3/157 Switch, passenger side airbag
4/9 Supplemental Restraint System module (SRS)
4/28 Transmission Control Module (TCM)
4/46 Engine Control Module (ECM)
4/56 Central Electronic Module (CEM)
4/58 Rear Electronic Module (REM)
11O/1 Fuses in spare fuse holder, passenger compartment (Alco-Lock only)
11O/2 Fuses in spare fuse holder, passenger compartment (Alco-Lock only)
16/65 Antenna ring/ignition switch illumination

Which is a lot of major stuff.

To determine which device is causing the fuse to blow, do the following:
1. Disconnect the vehicle battery
2. Remove the fuse
3. Measure with an ohmmeter between the fuse (fused side, not power side) to ground. A short will be close to 0 ohms.
4. Start unplugging the above listed devices one by one until you find the resistance changes dramatically.
5. If ALL devices are unplugged and the fault persists, then you have a wiring loom short to ground, caused normally by chaffing. Follow the wiring loom as shown in the wiring diagram until you find the short

NOTE:
Some devices will be hard to get to!
In order of my suspicions, start with disconnecting the Antenna ring/ignition switch illumination (easy), the ECM (easy), the TCM (also easy), then the rest

However I predict a wiring loom chaffing somewhere as the culprit, because control units normally do not suffer such major failure as to cause the fuse to blow so suddenly.
Especially as the problem has been intermittent.

A common place for chaffed wires is under the drivers seat, there is a loom there for radio/amplifier among other things.This is a photo of the loom with outer covering removed, look carefully at the 4th wire from bottom in line with the thumb the wire above the white one, you can see broken insulation which caused a short, the blue wire is also chaffed and the two may have shorted together.
Attachment 114409
(Photo was posted in another thread by another member a while ago)

Deleted.

jacobsdad, did you ever resolve your issue #11 fuse blowing?

My wifes '08 XC90 V8 just starated to blow that fuse, so I'd be curios to learn what became of your issue

Thx!
Marcel

Unfortunately Marcel I don’t think you will get to find out as he hasn’t been online according to his profile since he posted the original question in 2018.

Good luck finding out what the problem is.