VinCanary

Reliability report · 2020 Mazda CX-9 · Updated July 2026

The quiet middle year — the last one CSP11 covers, with the engine story shifting from coolant to oil.

The 2020 file is small, but it sits on a fault line. The cracked-cylinder-head coolant leak still surfaces, and 2020 is the last model year covered by CSP11 — a Customer Service Program extending the powertrain warranty to 10 years or 120,000 miles for that repair. At the same time, the complaint mix begins shifting toward the oil-consumption pattern that dominates 2021, and toward driver-aid faults (phantom braking, front-radar and Smart Brake Support malfunctions).

One recall applies: 21V750 (Mazda 5221I), covering 2020-2021 CX-9s with 60/40 split second-row seats, where the left-side seat can slide forward in a crash (a Federal Motor Vehicle Safety Standard non-compliance). The remedy is a free replacement of internal seat parts. This is a Chirping year: do a real engine check for both coolant loss and oil consumption, confirm CSP11 status while it still applies, and clear the seat recall by VIN.

Evidence: 19 NHTSA complaints · 1 recall campaigns · 7 mechanic & forum sources

Canary status

Chirping

What that means: 19 federal complaints — small — but the mix is the story: the cracked-head coolant leak still appears (and 2020 is the final year covered by Mazda's CSP11 warranty extension), the oil-consumption pattern is beginning, and one recall covers a second-row seat that can slide in a crash. A quiet, mostly-covered year that rewards a careful engine check.

CalmChirpingSquawkingFainted

19

Federal complaints

1

Recall

$0 (covered)

If CSP11 window applies

several thousand

Cylinder-head repair if outside CSP11 (owner/mechanic reports)

Known issues

Ranked by the cost of ignoring them. Every claim carries its source.

Cracked-head coolant leak (final CSP11 year) and emerging oil consumption

major
  • 2.5L turbo (SkyActiv-G)

The engine story is in transition on 2020. The cracked-cylinder-head coolant leak still appears in the file, and 2020 is the last year CSP11 covers it (powertrain warranty to 10 years or 120,000 miles, with reimbursement). Meanwhile the oil-consumption pattern that defines 2021 is beginning here — owners reporting the low-oil light between changes. Inspect for coolant residue at the back of the block, check oil level and consumption between changes, and confirm where the car sits in the CSP11 window, because after 2020 that safety net ends.

What to check

Pink and cleanServiced. Proceed.

Dark brownDamage underway.

Cylinder-head repair if outside CSP11 (owner/mechanic reports)

several thousand

If CSP11 window applies

$0 (covered)

Sources: NHTSA complaint database, 2020 Mazda CX-9 · NHTSA recalls + manufacturer communications (21V750, CSP11 window, campaign documents) · Independent mechanic and owner/specialist channel transcripts (CX-9 second generation, 2.5T)

Second-row seat recall (21V750)moderate

Recall 21V750 (Mazda 5221I) covers 2020-2021 CX-9s with 60/40 split bench second-row seats: the left-side second-row seat may slide forward unexpectedly during a crash, failing Federal Motor Vehicle Safety Standard 210 (seat-belt anchorages) and transferring excessive force onto a belted occupant. The remedy is a free replacement of the affected seat's internal parts; owner letters were mailed November 4, 2021. Confirm completed by VIN — this is the most common spot for a child seat.

Sources: NHTSA recalls + manufacturer communications (21V750, CSP11 window, campaign documents)

Driver-aid false activations (phantom braking, sensor malfunctions)minor

A recurring low-frequency pattern that becomes more visible as the engine noise fades: the i-ACTIVSENSE suite throwing 'Smart Brake Support malfunction,' front-radar-sensor and forward-collision faults, sometimes with a brief loss of acceleration, and occasional phantom braking with nothing ahead. No recall. Test the automatic emergency braking and adaptive cruise on the drive, and pull codes if the dash shows any safety-system malfunction history.

Sources: NHTSA complaint database, 2020 Mazda CX-9

2020 is the last CX-9 year Mazda's cylinder-head warranty extension (CSP11) reaches — and the year the engine complaints start shifting from coolant leaks to oil consumption.
7 mechanic & owner sources

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  1. 21V7502020-2021 CX-9 with 60/40 split second-row bench seats: left-side second-row seat may slide forward in a crash (fails FMVSS 210). Free replacement of internal seat parts; letters mailed November 4, 2021. Mazda code 5221I.open

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