There is a canbus ecu on the bulkhead, behind the right hand side battery box. ( My D3 battery is in the right hand side, the brake pipes and stuff are are in the left box where us in the UK, fit a 2nd battery ) that can get water in. Remove the cover, and check all the 3 plugs. The centre one is a blue colour and is the usual suspect for corrosion on the pins. Clean them and silicone gel the plugs to stop the issue.
The rear upper arms can show wear on the bushes, the best bet is to upgrade to RRS uppers, ( i have done this ) as they are stiffer and last longer.
At the same time, check the rear lowers, if the uppers have wear, so will the lowers, While they are out, change the hub bushes.
The hub bushes creak when they are worn, i have had the upper and lower arms changed, but forgot to do the hubs, so now i need to get them changed as well.
I had the arms changed at 117k, it's on 134k now and running as sweet as ever.
Mine does get a very hard life but i only fit genuine parts for replacements.