P011AEngine Coolant Temperature Sensor 1/2 Correlation
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- Some engines have two coolant temperature sensors that check each other. P011A is set when both are electrically fine but their readings differ more than a calibrated amount under conditions where they should agree. Mazda documents the code for the 2013–2016 CX-5 and 2014–2016 Mazda6: sensor 2 sits in the heater hose, and a clogged heater core keeps it noticeably colder, so P011A often comes with weak cabin heat although both sensors are good. Mazda's check is to compare both sensors with ambient temperature after an overnight soak and then the temperature difference across the heater hoses. A block heater used below 0 °C can also trigger it.
- What you may notice
- Check engine light on
- Weak cabin heating (typical on Mazda)
- Otherwise often no driving symptoms
- Likely causes
- LikelyClogged heater core or restricted coolant flow at sensor 2
- PossibleOne of the two sensors drifting
- PossibleAir in the cooling system or low coolant level
- RareBlock heater use in frost
- RareContact resistance at one sensor
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €50 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.