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2004 Hyundai Sonata Loses Power while Driving!

Hello experts,

I was driving my Sonata this morning to work as usual. It was a wet morning but not raining. I hit a pothole (which I've hit before) going 35-40 mph. About 1-2 minutes later I was driving about 30-35 mph when I heard a click, lost power and then everything came back on. I believe during this "power loss" that I couldn't accelerate since I remember the rpm going down but I know that I took my foot off of the accelerator when this happened. I kept driving to work and about 2-3 minutes later while coasting down a hill at 35-45 mph. It happened really fast twice in a row. Each time there was a click, the lights would dim or shut off completely (not sure since it happens so fast), the check engine light would flash, and I believe the radio turned off. Since it happened so fast (click, shut off, and back on) I didn't get to see if I could keep driving (accelerate) or if power steering was gone. I am guessing that they would be gone with my limited knowledge of what I was experiencing. I was able to drive 8 minutes to work without it happening again. I popped the hood looking for a loose connection around the battery but nothing was popping out at me. My car has 117,000 miles and has regular maintenance done. Any ideas or ways I could diagnose it further? Can O'reilleys check the code that flashed on and off if it isn't on anymore? Thoughts? Let me know what other information you might need.


Yes, the codes should be stores in the car’s computer. Have it read for free at the car parts store and post back.

Thanks Galant, I will do that.

Took the car over to a mechanic who tried to read the codes but the car didn’t store them. Checked the battery and it read good. Mechanic said if it happens again to drive it straight to them and don’t turn off the car. He said it could be a bad sensor? During all this driving it didn’t happen again. If anyone has any ideas of more diagnostics, that would help. Otherwise I guess I will have to wait till it happens to me again which I don’t like the sound of that.

Update: I went to leave work this evening and couldn’t start my car. I could put the key in and turn it. the engine sounded like it wanted to start but it wouldn’t turn over. The check engine light turned on and stayed on. I got the engine to turn over once when I hit the accelerator while turning the key but it shut off immediately after. My dad thinks it might be a fuel issue (bad fuel pump). I had the vehicle towed to a mechanic this evening who will look at it and give me a diagnostic tomorrow sometime. I will post here once he tells me what’s going on.

Update: The mechanic said I had a bad cam sensor and crankshaft positioning sensor. They are going to replace them for $575 (not sure if this price incl. parts). The mechanic seemed very confident that this was the problem and that they see this a lot with “newer” vehicles. I guess I’ll see what happens.

Hi Eric, my wife’s car is having a similar problem. Did replacing the cam sensor and crankshaft positioning sensor fix the problem? All the best, Ty Pike

The check engine light turned on and stayed on.

That’s normal. It will turn on when you put the key in “on”, then it should turn off once the engine is started and running.

It seems sort of unusual that both sensors would fail at the same time. Does your mechanic say they’ve seen this before, both sensors failing at the same time?

This thread went dormant in May of 2015. TyPike needs to start his own thread.

This happened to me with my 2013 Hyundai Sonata. We had to replace the starter.