P111A on Mazda: How to Diagnose & Fix
Engine Coolant Over Temperature Condition - Forced Limited Power
1 Mazda model · 1 documented issue · 1 critical · $2,300-$9,500 repair
P111A on Mazda by model: symptoms, diagnosis and fix
The turbocharged 2.5T cylinder head can crack in the aluminum casting near the exhaust manifold flange / stud-bolt holes, where thermal load concentrates. This produces a slow external (and sometimes internal) coolant leak: the reservoir drops with no obvious puddle, a sweet coolant odor appears after shutdown, and white crystallized residue forms on the exhaust side of the head. Left unaddressed the crack widens with heat cycles and can lead to overheating and engine failure. Mazda documented it across TSB 01-013-21, 01-007-22 and 01-002-23, and it is the subject of a U.S. class-action lawsuit covering 2019-2024 CX-5 (and CX-9/Mazda6).
Common Symptoms
- Coolant level dropping with no visible puddle
- Sweet coolant smell after driving
- White/crystallized coolant residue near exhaust manifold
- Overheating or temperature gauge climbing
- Low coolant warning
How to Fix
Confirm the leak source at the exhaust side of the head (not a hose or water pump). The fix is replacement of the cylinder head assembly with the revised service part (Service Alert SA-058/20) using updated gaskets that redistribute load to the exhaust manifold; severe cases need a long-block/engine. Qualifying VINs built before June 2020 may be covered under Mazda's goodwill Customer Service Program (reported as CSP11, up to ~10yr/120k mi) — check VIN eligibility before paying out of pocket. Out-of-warranty head replacement runs into the thousands; full engine replacement can reach $5,000-$10,000.
Sources for this issue (3)
P111A code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P111A mean on a Mazda?
P111A stands for "Engine Coolant Over Temperature Condition - Forced Limited Power." Mazda-specific code seen across SkyActiv-G gasoline and SkyActiv-D diesel engines. The PCM watches engine coolant temperature through the ECT sensor and sets this code when coolant temperature exceeds the calibrated over-temperature threshold (Mazda service information cites roughly 122 C / 252 F) for a set period. To protect the engine, the PCM forces a reduced-power mode. The driver typically sees the high coolant temperature warning light plus a noticeable loss of power. This is a protective action, not a nuisance code - the engine is either actually overheating or the PCM believes it is, and continuing to drive risks head gasket or piston damage. Note that Mazda issued service information for 2014-2015 Mazda3 vehicles where this set from a sensor/wiring fault rather than true overheating. On Mazda it is documented across 1 model: CX-5.
What are the most common causes of P111A?
The most common causes of P111A are: Low coolant level or air trapped in the cooling system after a leak or service, Failed or stuck-closed thermostat, Cooling fan or fan control module not commanding the fan on, Faulty engine coolant temperature sensor or its wiring reporting false high readings, Failing water pump or a restricted/clogged radiator, Head gasket failure pushing combustion gases into the cooling system. The specific cause varies by vehicle.
How much does it cost to fix P111A on a Mazda?
Published repair estimates on Mazda range from $2,300 to $9,500 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P111A on a different make?
View P111A across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.