What it means
The system voltage feedback of the coolant heater A control module is outside the expected window.
At a glance
- Usually lights the check-engine light
How it works
The control module for coolant heater A monitors a feedback signal representing system voltage. P2DA7 sets when that feedback falls outside the expected window, which can prevent the heater from operating even if its heater element is intact.
Common causes
Most likely first.
- System voltage drifted
- Feedback wire fault
Symptoms
- Coolant heater may not operate
- Reduced cabin heating in cold weather
How to diagnose it
- Record freeze-frame data and check live system-voltage feedback for coolant heater A alongside the vehicle’s reported system voltage.
- Check whether heater A is commanded on and whether its status changes, noting whether the fault appears only during starting or other voltage changes.
- Inspect the heater control module’s feedback wire and connectors for damage, corrosion, loose terminals, or a poor ground.
- Test the feedback circuit for an open, short, or excessive resistance using the wiring diagram and compare readings with the manufacturer’s specification.
- If wiring and vehicle system voltage are within specification, follow the manufacturer’s procedure to check the heater control module’s voltage feedback function.
Common fixes
- Repair a loose, corroded, or damaged feedback-wire connection at coolant heater A.
- Repair an open, short, or high-resistance fault in the feedback circuit.
- Correct a vehicle system-voltage problem if live data shows voltage drift outside specification.
- Replace the coolant heater A control module if its feedback remains incorrect with sound wiring and correct system voltage.
Can I keep driving?
Driving is generally possible if the vehicle has no other warnings or drivability problems, but coolant heater A may not operate and cabin heating can be reduced in cold weather. Follow any hybrid-system warning that calls for stopping.
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.