2009 Mazda CX-9: what breaks, and at what mileage

What breaks on the 2009 Mazda CX-9

Owners have reported 21 named failure modes on the 2009 Mazda CX-9, and the three most-reported carry 39% of everything filed.

Airbag inflator rupture leads with 11 reports and about 0.5 per 1,000 vehicles.

Master cylinder or brake booster failure follows with 8 reports, usually reported between 87k to 120,000 miles.

Differential or transfer case failure follows with 7 reports, median 105,000 miles.

By system, the reports fall mostly into brakes (16), airbag (12) and drivetrain (7).

What happens when these parts fail

Across the named modes, 1 mentions a crash. Those are the words owners used in their own complaints, and NHTSA does not verify them, but they are the closest thing in this data to a measure of what a failure actually did.

The average severity weight across every report on this year is 4.68, where a stalled engine or a failed airbag weighs many times more than a rattling trim panel, and a figure this high means the reports are dominated by failures with safety consequences rather than annoyances. The weighting is set out in full on the methodology page.

What the top failures cost to put right, as editorial estimates for an independent US shop rather than figures from NHTSA: airbag inflator rupture at $0–$0, master cylinder or brake booster failure at $450–$2,200, differential or transfer case failure at $900–$4,200 and other brake problem at $300–$1,800. Dealer labour, a seized bolt or a part that is no longer made can push any of these past the top of its range.

21% of the reports on this year sit in the engine, transmission, drivetrain or cooling systems — the four where a repair bill is usually four figures.

How often, against how many were built

Scaled by an estimate of how many of these cars exist, the 2009 Mazda CX-9 draws about 2.7 per 1,000 vehicles, which puts it in the 84th percentile of complaint rates among 2009 vehicles we can rate.

That denominator is the weakest number on the page and it is fair to say so plainly. Rate per 1,000 uses a fleet-size estimate derived from recall paperwork for this exact model year. It is a lower bound.

The working figure is 24,185 vehicles. If the true number is twice that, every rate on this page is half what it says; the ranking against other 2009 vehicles, which is what the risk score uses, is far more robust than the rate itself.

Recalls on the 2009 model year

NHTSA has issued 7 recall campaigns covering the 2009 Mazda CX-9, affecting an estimated 71,340 vehicles. A recall is a different kind of evidence from a complaint: it is the regulator and the manufacturer agreeing that something has to be fixed, and the fix is free for as long as the car exists.

The campaigns cover air bags:frontal:passenger side:inflator module. Whether the work was actually done on the car in front of you is a question only the VIN can answer, and the manufacturer or NHTSA will answer it free.

One caution about reading these together: a recall usually raises the complaint count for the same part, because owners who read about it go and file. The mileages stay informative; the counts get noisy.

Better and worse years of the same car

High risk for a 2009 — 182nd riskiest of the 295 2009 vehicles we can rate. Every score on this site is a rank inside its own model year, which is what makes a 2004 and a 2019 comparable at all.

Across the 16 model years of this car that carry enough reports to score, 2007 comes out best at 64 and 2018 worst at 82, with 2009 itself at 69.

If the model year is negotiable, 2007 and 2023 score lower than 2009 by a margin worth acting on. Same body, same engines, different luck — usually a supplier change or a mid-cycle fix, which the complaint data can show but never explain.

Within the 2007–2015 generation specifically, 2007 is the strongest year at 64 and 2010 the weakest at 74.

What to look at before buying one

The mileages below are where the first quarter of reports for each mode had already been filed, which makes them the point at which a fault is worth looking for rather than the point at which it happens: master cylinder or brake booster failure from about 87k.

On a 2009 Mazda CX-9 with more miles than that on it, the useful question to put to a seller or a mechanic is whether master cylinder or brake booster failure has been dealt with, and if so with what parts and at whose expense. A car that has already had the repair is in a different position from one that has not.

Treat it as where to point the inspection, not as a prediction. A well-maintained example can sail past every mileage on this page, and a neglected one can fail well before the first of them.

The limits of complaint data

66 owner reports; fleet size estimated from this year's own recall paperwork. Every count on this page is therefore a floor: it is the number of owners who went to the trouble of filing with a federal agency, which is a small and self-selected fraction of the owners who had the fault.

Of those 66 reports, 43 carried an odometer reading, so the mileages here describe 65% of the sample rather than all of it. Owners also round: readings pile up on multiples of ten thousand, which is why this site publishes "about 90,000 miles" and not "91,438".

The failure modes are assigned by software reading the owner's own words, which is accurate in bulk and wrong in individual cases. A mode with a handful of reports may contain a misfiled one.

And nothing here predicts what one car will do. These are other people's complaints, filed years apart, on cars maintained by strangers. Read the page as a map of where this model year has previously gone wrong, then have the specific car in front of you inspected.