2013 Mazda 3 Manual Trans. Headlights Bright/Dim when Slowing
 

2013 Mazda 3 Skyactive Manual Transmission

I've had an odd problem come up. The car just passed 50,000 miles.

Recently, when I decelerate with the clutch engaged (engine braking), my headlights go through several cycles of becoming dimmer and brighter, before returning to normal. The dimming-brightening cycles occur at intervals of around 1 second... perhaps a bit less.

This happens only when slowing down with the clutch engaged. I notice it especially when downshifting into 3rd and 2nd gears. Or it will happen if I remove my foot from the accelerator but without depressing the clutch pedal.

It doesn't occur noticeably in 1st gear (although I would not normally downshift to 1st gear, I've done some tests, just to see if the same thing happened.) And I've not noticed it when downshifting into 5th or 4th gears, although it might(http://mazda3revolution.com/forums/i...milies/huh.gif)

I don't know if this is actually a problem or not. By itself, it's not... but might relate to some other underlying issue. I didn't want to drop it off at a dealer, in case they aren't familiar with the problem, to go on a "hunting" expedition. I was hoping I'd have some idea of what the problem is first. Any ideas?

When did it last yo into Mazda for a software update?

Hey there, I work for a Mazda dealership as a auto tech and there is a tsb for something similar to this for your vehicle. When the brakes are applied the headlights may flicker or dim, it is due to incorrect logic sent from the pcm to the alternator resulting in headlights cutting out when the brake lights are applied under load. The fix is pretty simple and we re flash the pcm with new logic. Just bring it to a local mazda dealership and inquire about it. In yours it dosnt say you are applying brakes but perhaps when the vehicle is slowing the alternator still can't keep up.

Thanks for the recommendation. I just remembered today that I hadn't replied.
The fix you suggested worked! I took my car for a software upgrade, and the problem vanished immediately! The engine seems to run better as well. (Guess I was overdue).
Exactly right... it didn't happen when i was braking, but when I was slowing down with the clutch engaged. All good now.

Glad we could help out.

Its amazing the number of minor issues that get fixed by regular software updates.

People are always updating software on their Phones & PC's, but they forget about their poor cars.