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I have a 2010 MazdaSpeed3 and I'm having a problem with the cruise control. It works perfectly on level terrain and up moderate hills, but if the car travels down a hill steep enough that the cruise control lets completely up from the accelerator in order to maintain it's speed down the hill then after the hill levels out, cruise control lets the speed drop 10 to 15mph below where it was set to and then deactivates itself. If you press the resume button it returns to the speed it was previously set at. It ONLY does this anytime cruise control lets complete up off the accelerator. What could be wrong? It's done this since day one when it was brand new. Now it only has 3,600 miles on it.
Year: 2010Make: MazdaModel: Speed3Engine: 2.3 turbo Already Tried: Nothing. Took it to the dealer and they said they've seen nothing like this problem. They have no idea what's wrong. Gotta leave it with them so the can experiment with it. AThey acknowlege the problem though.
Hi! my name is XXXXX XXXXX X can help. Your vehicle uses a accelerator position sensor, that sends a signal to two separate throttle position sensors on the throttle body (what controls the acceleration) The throttle body uses an electronic motor to set the correct desired speed, whether it be from you just stepping on the gas pedal, or the computer commanding it via cruise control. First of all, one of your throttle position sensors, or accelerator position sensor has failed, all should be monitored via a Mazda scan tool by the dealership on a road test. May be helpful to go on a road test with them, to show them where exactly it is happening. If an inconsistency is seen in any sensor (will be shown on detailed graph to compare)that is where the problem lies (or the sensor has failed) Most importantly, being a 2010 model, the computer the vehicle uses may not be able to understand some circumstances, such as described, and default to minimum allowable speed for cruise control. Your dealer should have already contacted an engineer about the problem. Thanks so much, and I recommend printing and discussing my answer with the dealer. Nick.
Okay I took it back to the dealer yesterday. I rode with him to make sure he was seeing the problem that I was having. He spent a full day test driving and calling Mazda running all sorts of diagnostics. He also stated he has no idea how to repair such a problem and can only run the diagnostic test that Mazda sends him through being that the car is so new and under warranty. They gave me my keys back at the end of the day and told me that they weren't able to fix the problem. I called three other dealerships and they all told me that they have never seen such a problem, and that anything they would do to it would only be experimenting. I am so frustrated. I've bought the car brand new five weeks ago, and I want another car. This one stays in the shop or on the road to the shop more than it stays in my backyard or on the road for my trips.
By the way the mechanic told me he had made an adjustment to the cruise control switch on the brake pedal. It wasn't until I almost wasn't until I was almost rearend twice on my way home that I decided to stop at a gas station and check the brake lights, only to discovery they would only work if the pedal was press halfway to the floor :(. I live like 97 miles from the closest Mazda dealer, so I had to fix the problem myself.
I'll call the dealer today and tell them what you have said to check and ask them did they do so. I really appreciate you spending the time to look into this.
Would you have any other suggestions?
No problem.
A good technician should be able to take the theory of how a system works, and diagnose from there on. (Understand the engineering and systems). The fact that they
told you they can only do tests Mazda recommends means they are not competent.
I recommend contacting Mazda directly, and research the Lemon Law (Buy Back)
Thanks so much, and keep me updated!
Once again, an accept is highly appreciated, and I will continue to assist you regardless of accept status.
Thanks
Nick.
ASE Certified Technician
Ford Drivetrain and Chassis Master, ASE Master Technician