2012 Mazda CX-9 Problems

What owners report

Owners of the 2012 Mazda CX-9 most often describe a power brake booster problem: the pedal turns hard, a hissing noise appears, and extra effort is needed to stop. Complaints also describe engine stalling, often linked by mechanics to an internal water pump failure, and misfire-free sudden stops where no warning light came on beforehand.

1. 1
   Brakes

   Hard brake pedal with hissing noise (brake booster)

   • 121 complaints (55%)
   • median 57,000 mi at 4.8 yrs old (103 state mileage)
   • 3 mention a crash, fire or injury
   • filed 2013–2023

   Owners describe the brake pedal becoming stiff and requiring far more force to slow the vehicle, often with a hissing or air-escaping sound near the pedal when it is pressed. Some say the first press feels normal and later presses in stop-and-go traffic go hard, and several report the pedal sometimes releases and the car jerks to a stop. Complaints describe mechanics diagnosing a failed vacuum power brake booster or master cylinder; several owners mention a warranty extension program for the booster rather than a recall, and some say their dealer found nothing wrong on an early visit. Reported across a wide range of mileage, from around 12,000 miles to over 140,000, with many appearing between roughly 50,000 and 100,000 miles.

   1 related service bulletin

   What to check: Press the brake pedal repeatedly with the engine running and listen for a hissing sound; a pedal that goes hard and stays hard is worth having inspected. Ask whether the power brake unit was ever replaced under any extended warranty program.

   2 excerpts from owner complaints in NHTSA records

   “I was driving slowly about 30miph and began hearing a hissing noise when I depressed the brake pedal. Once I pulled into my driveway a small incline, and pushed the brake pedal it was very tight and stopped at a point, but would not go further, tried shifting different gears. Finally brake depressed. Hissing has continues, very stiff brake pedal”

   NHTSA complaint #11365716, filed 2020-10, 54,000 miles

   “My break pedal feels as if it becomes stiff and I hear a hissing noise coming from the pedal. My breaks will not slow the vehicle. I have to remove my foot and reapply pressure forcefully in order for the breaks to work. It does this in reverse, going down an incline or flat surface. This happened while my child was with me. Please repuireva recall or lives may be at stake.”

   NHTSA complaint #10985523, filed 2017-05, 143,000 miles
2. 2
   Engine

   Engine stalls or shuts off while driving

   • 33 complaints (15%)
   • median 55,733 mi at 6.0 yrs old (30 state mileage)
   • 2 mention a crash, fire or injury
   • filed 2013–2023

   Owners report the engine cutting off without warning at traffic lights, at low speed, or while decelerating, sometimes restarting and sometimes not for several minutes. Several complaints say mechanics traced a stall and subsequent power loss to the water pump failing and coolant entering the engine, with quotes for engine replacement. Other owners describe the dealer being unable to reproduce or diagnose the stall. Mostly reported between about 65,000 and 175,000 miles, often at low speed or while coming to a stop.

   5 related service bulletins

   What to check: Ask for service records and whether the water pump or cooling system has been serviced, and check for coolant loss or a low coolant level. A pre-purchase inspection that checks for stored codes and coolant residue is worth the cost.

   2 excerpts from owner complaints in NHTSA records

   “Incident -1 traveling about 45 MPH decelerating to make a right turn, the car stalls out leaving me with no control of steering and little ability to brake. Incident 2- making right turn (decelerating) car stalls out leaving me with no steering and little braking control. Incident 3- pulled up into driveway on slope. Put the car in reverse to back out, car stalled out leaving me with very little ability to brake.”

   NHTSA complaint #10546909, filed 2013-10, 12,000 miles

   “In oct. 2019 my cx9 stopped while being driven. Found out the water pump (which is inside the engine) had gone out and destroyed my engine. This is a known problem of which Mazda has failed to make their consumers aware. I purchased this care new and all of my services had been handled by Mazda. No-one told me about this problem and I still had to pay just over 4k to get a new engine of the same stupid design put in my car. This is very dangerous problem. …”

   NHTSA complaint #11331950, filed 2020-07, 170,000 miles
3. 3
   Vehicle speed control

   Sudden acceleration or unintended revving

   Mentioned in 5 of 60 sampled complaints

   Owners describe the engine revving or the vehicle surging forward while their foot was on the brake, in one case while pulling into a parking space and in another at a stop light. Some reports pair this with the accelerator feeling stuck or unresponsive at low speed in reverse. Complaints say the cause was not determined and that the dealer or manufacturer was not able to explain it. Reported from about 4,000 to 56,000 miles, typically at low speed while parking or stopped.

   What to check: During a test drive, check that engine speed settles when idling in gear and that pedal response is smooth from a stop. Ask whether any throttle body cleaning or pedal sensor work was done.

   2 excerpts from owner complaints in NHTSA records

   “I had an incident yesterday resulting in a minor collision. My accelerator stuck, my engine kept revving, and I could not stop. I kept applying the brakes but it felt as if everything locked up. I rearended the person in front of me no damage to their car and only minor to mine. I am now afraid to drive the vehicle. My husband contacted the dealership and they are waiting to hear back from Mazda corporate.”

   NHTSA complaint #10493756, filed 2013-01, 15,049 miles

   “I am unsure of the first date of occurrence, but the following have been happening since I purchased this vehicle new with 12 miles on it. And the dealer can't find anything wrong with it. 1. The AC always comes on. Even when it's below zero outside. 2. It fails to go when pushing on the accelerator frequently, and especially in reverse, from a stopped position, until you really push hard on the accelerator causing it jump. 3. …”

   NHTSA complaint #10566281, filed 2014-02, 4,000 miles

Buying note. A pre-purchase inspection should focus on the brake booster and pedal feel, cooling system condition, and, on AWD models, transfer case noise and fluid condition. Records showing completed airbag inflator recalls and prior brake or cooling repairs are the most useful paperwork to ask for.

Summary written with AI from a sample of 60 NHTSA complaints for this model year (picked at random, with complaints that state a mileage and recent ones taken first), then checked automatically against the source records. Where a problem shows a complaint count, every complaint for this model year was matched with fixed keyword rules (written with AI and tested against the sample), and the mileage, age and repair figures are calculated from those complaints; owners' figures are as stated, not verified. Other counts refer to the sample. The excerpts come from NHTSA's public complaint records and are unverified; capitalisation is normalised, NHTSA staff notes are removed, and shortened text ends with “…”. Something wrong? Request a correction.