I should probably start this by mentioning that I have replaced the timing belt, battery, sparks plugs and coils in the last 3 months. This is a 2006 s40 non turbo.
I saw a warning about urgent engine maintenance a couple of months ago and it went into limp mode. I forget what it said but it was not the power system error. It seemed to be running fine though prior to this message.. It went away after restarting the engine.
My car now will lose power when driving. All the dash lights come on. It loses power. I coast to a stop. It doesn’t start again unless it has sat for a while. The engine will turn over every 10th try or so. It doesn’t stay on though. I thought this might be the starter module. I had it towed to my mechanic friend and it started right up. I left it with him for a week. He says it started fine every morning. He would let it run for a while. It didn’t lose power. The hiccup seemed to be gone. It does not seem to be the starter module. I drove it for a couple of hours. Things were fine. I stoppped for a couple of hours. I got back in it and it started fine and ran fine. After a few miles (like 3) the engine lost power. All the lights came on. I left it for a couple of hours. It started fine after a couple of tries and it ran well after that. I got it where it needed to be (maybe 10 miles). It hasn’t started since.
I believe it’s also worth noting that I have water in the interior. I have seen the video about fixing this but haven’t done the fix yet. I believe something may be corroded or have a short from the interior water. It is VERY cold here.