Hey all, new to this awesome group.

So, I have a 2009 Fit Sport Automatic with about 90k miles on it. It's been working fine until recently. If I drive it for any long distance at highway speeds, eventually the check engine light starts flashing and I have to slow down as the car locks me into 1st gear. If I leave it for about 10 min or so, I can start it up again and no problem.

I went to a trusted mechanic and he said it might be a low voltage issue from the alternator (when I drive, I have several accessories plugged in (I'm an Uber Driver) as well as A/C and stereo). He said when this happens, try the windshield wipers on max and see if they are moving normally or slowly. They move slowly.

So, I replaced the alternator. The battery is brand new as well. I thought all was well, but the problem came back last night and I am positively stumped.

Mechanics have said that there doesn't seem to be anything wrong with the transmission, and the catalytic converter seems okay as well.

Any thoughts from the community would be extremely welcome. Thanks!

 

A flashing check engine light means there is a misfire. Did the "mechanic" even scan for codes? I would pull the plugs to see what they look like.

You need a new mechanic too.

 

Unfortunately the codes didn't reveal anything anything telling. I'll be bringing it in on Monday to see what else they think could be causing the problem, but wouldn't it be odd to only get misfires after an hour of driving? And that stopping the car for a few minutes would correct the misfire?

 

If the original coil packs are still in there I would suspect those since they are a known weak spot on the fit.

 

The behavior doesn't really sound like the coil packs to me, but I will definitely look into it. Thanks.

 

My thought is that your mechanic is not to be "trusted." All he had to do is look at the freeze frame data that your OBDII stored when your light started flashing. Even the cheapest OBDII reader can read that information and that information is there even when the MIL turns off. It would tell him, among other things, what the voltage was at the time of the problem, so an alternator could easily be ruled in or out. It would also tell him what cylinder(s) had misfires and also information about fuel trim, etc. to help diagnose. To get you to replace your alternator on a whim is laughable. The fact is that if it starts easily after this event, it would be very surprising that an alternator failed. Simply put, our batteries are tiny, and without an alternator charge for any length of time, the battery would not have the power to start the car.

Any mechanic who recommends replacing any part with no diagnostics is not a mechanic at all. He is a parts replacer. Those people often are cheap in their labor fees, but make it all up by replacing unnecessary parts. They might be fine changing the oil on a good working car, but not for diagnostic work.

The most important things to look at, assuming nobody cleared the codes, or the battery was disconnected are: 1. The freeze frame data 2. What codes set during the misfires. 3. Look at the misfire data to see if it is one cylinder or all the cylinders that are misfiring. It's also necessary to look at the mode $06 data. That is the data that your computer looks at to determine whether or not to turn on the MIL. That can show you borderline problems that exist before the MIL turns on, and also prove later that the problem was really fixed, instead of having to wait several drive cycles to see if the light comes back on.

The coils that someone spoke of were a real problem in the 1st generation Fit, not so much the 2nd generation such as your 2009. Still, if the problem is confined to one specific cylinder, that, and/or the spark plug for that cylinder would be prime candidates for this problem.