Hi. I have 2011 S40 that has been very reliable. A couple of weeks ago I was driving and "headlight failure" came up then "anti skid service required" came on the screen then a red triangle with "brake failure - stop safely". Then the revs die to tickover and the clocks go to zero. I turned it off for a few minutes then started up and drove a bit further and the same thing happened again. Each time I drove I got less distance. I've had the general diagnostics checked that showed several comms faults which pointed to the body control module so I got a replacement and had it programmed only for the same faults to show up in the same order, so £250 later that was obviously not the problem. I have unplugged the ecu to check for damage and plugged it back in and also cleaned three earth straps in the left front wheel arch. Now it is showing "immobiliser fault" and not starting.
Before I throw even more money at this I wondered if anyone has had the same faults coming up and might have an idea how to fix this. I do not want to scrap the car, just had new clutch, flywheel, master cylinder, discs and pads. Any advice would be greatly appreciated. Thanks.

 

For all the world it sounds like a typical alternator failure. Any time (!) you get random, seemingly unrelated faults popping up, it's nearly always low battery voltage. Your symptoms fit that scenario to a tee, also (battery recovering, but for less distance every time).

Just get a cheap multimeter (literally just a few bucks) and check the battery voltage with the car off (should be at least 12 volts) and running (should be around 14 volts). Or if the thought of touching test leads to a battery horrifies you, just get ...

 

Thanks for this advice, I will try that but I've also fitted a brand new heavy duty battery within the last 12 months, so it could be the alternator. I will try a jump start and check the running voltage if it starts. I'm hoping this won't be a process of elimination that might end up with me throwing money into a bottomless pit. I will definitely try this though. Next step might be to pay for a full electronic diagnostic and hope it pinpoints an ecu or something rather than a wiring fault which could take forever to diagnose. Thanks again, much appreciated. I'll post on here what happens.

 

I'm thinking it could also be the CEM. Check out Xemodex's web site for some tips on symptoms and diagnostics.

 

Thanks for this info. I tried jump starting the car but it still came up with "immobiliser fault" and wouldn't start so I'm presuming it's not the alternator. I will look on Xemodex's website and see if I can figure anything out from there. Thanks.