What it means
Coolant heater A reports temperature above the protection threshold. Coolant flow blocked or thermistor failed.
At a glance
- Usually lights the check-engine light
How it works
Coolant heater A heats coolant and monitors its own temperature to protect the heater from overheating. P2DA6 sets when the reported heater temperature exceeds its protection threshold, which may happen if coolant flow is restricted or the thermistor reports incorrectly.
Common causes
Most likely first.
- Coolant flow through heater blocked
- Thermistor failed
Symptoms
- Check-engine or hybrid-system warning light may be on
- Coolant heater may shut down or operate intermittently
- Cabin or engine warm-up may take longer in cold weather
How to diagnose it
- Record freeze-frame data and check coolant heater A’s reported temperature and operating status to see whether it overheated during a heater command.
- After the system has cooled, check the coolant level and look for leaks or signs that coolant flow through heater A may be restricted.
- Inspect accessible coolant hoses and connections serving heater A for kinks, collapse, blockage, or damage.
- Inspect the heater temperature sensor wiring and connector for loose terminals, corrosion, or damage that could distort the temperature reading.
- If coolant flow appears normal, compare thermistor readings with actual temperature using the manufacturer’s diagnostic procedure and specification.
Common fixes
- Restore coolant to the correct level and repair any leak, following the vehicle’s specified filling and bleeding procedure.
- Repair a kinked, damaged, or obstructed coolant hose that restricts flow through heater A.
- Repair the temperature sensor connector or wiring if it is damaged or has a poor connection.
- Replace the failed thermistor or coolant heater A assembly if testing confirms the component fault.
Can I keep driving?
Do not keep commanding the heater if it repeatedly overheats; let the system cool and address the fault before relying on it. The heater may shut down, leaving slower warm-up, and an underlying coolant-flow problem may affect other parts of the cooling system.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.