2013 Mazda 3 Loses Power

Question

I have a 2013 Mazda 3 i Touring sedan 2.0L SkyActiv G 6-speed automatic, with about 40,000 miles on it. This has been happening for about two months maybe. But very intermittently, particularly when driving at highway speeds.

My car will lose power (feels as if the engine is not getting enough fuel, I mean) as I try to accelerate. I have not tried depressing the pedal all the way when this happens because since I first thought of trying to see how far I have to depress it hasn't happened again (just in the past few days). What I usually do is just take my foot off the accelerator and then put it back on, and it's back to normal. Though 4 days ago it happened three times in a row; it lost power, took my foot off, back to normal, then happened again after a few seconds, etc.

In conjunction with this the CEL will come on (I got the code read and it's P0571). The cruise control also will no longer engage (this issue seems to be persistent). I've checked the battery, it reads 12.53 Volts. I tried to check the spark plug gaps, but they were in too tight to get out by hand (actually cut myself just trying to get a bolt off to even get to one of the spark plugs). I visually inspected the SAS fuse, in case it's an ABS issue, and it looked fine, definitely hadn't blown.

Looking around online it looks like the other most likely issues are the brake light switch, the throttle body, ABS sensor, or the alternator. Do these seem likely? Are there any other components that are more likely?

Any advice would be really helpful! Thanks!

Answer 1

Like you said, the P0571 is for the cruise control. There are several things which could set this code:

• Faulty Brake Switch
• Misadjusted brake switch
• Brake Switch harness is open or shorted
• Brake Switch circuit poor electrical connection

I'm going to take an educated guess that the vehicle is drive by wire (DBW), meaning that the you press the gas pedal, which sends a signal to the engine control unit (ECU), which then tells the throttle body to open up whatever it translates your actions into. IOW, there is no direct connection between you and the throttle.

Because of this, I'm guessing the ECU is seeing one of the above list items as a fault and is reacting via the throttle body because of it. It's also the reason why the cruise control isn't working.

To fix this, you'll need to figure out what is setting the code. Due to the symptoms, I'd suggest it might be because the brake switch harness is shorted or becomes shorted, but that's only a guess.

Since your vehicle is still under the powertrain warranty (6yr/50k miles if here in the States), I'd suggest you take it to the dealership and have them sort it out. It should be covered because this is affecting the driveability of the vehicle (this is not a guarantee, so ask them before you give it to them).