P2DA5: Coolant Heater A Supply Voltage Circuit

What it means

Coolant heater A supply voltage circuit reports a fault. Heater may not start when commanded.

At a glance

• Usually lights the check-engine light

How it works

Coolant heater A uses a dedicated supply circuit to power its heater and control electronics. P2DA5 sets when the supply circuit reports a fault, so the heater may fail to start when the vehicle commands it.

Common causes

Most likely first.

1. Supply fuse blown
2. Wiring fault

Symptoms

• Check-engine or hybrid-system warning light may be on
• Cabin or engine warm-up may take longer in cold weather
• Coolant heater may not operate

How to diagnose it

1. Record freeze-frame data and check heater A command and status with a scan tool to confirm whether the heater was requested when the fault occurred.
2. Inspect the coolant heater A supply fuse and its terminals for an open fuse, poor contact, corrosion, or heat damage.
3. With the vehicle made safe according to the manufacturer’s procedure, inspect the heater’s supply wiring and connectors for breaks, chafing, moisture, or loose terminals.
4. Measure supply and ground at the heater connector during a commanded test and compare the readings with the manufacturer’s specification.
5. If the fuse, wiring, supply, and ground are correct, check the heater control module and heater assembly for an internal electrical fault.

Common fixes

• Replace the failed supply fuse after checking for a short or overload that caused it to open.
• Repair damaged or corroded supply wiring and connector terminals for coolant heater A.
• Correct a poor ground or high-resistance connection in the heater circuit.
• Replace the heater or its control module if testing confirms an internal fault.

Can I keep driving?

If the vehicle has no other warnings or drivability problems, it can generally be driven, but coolant heater A may not operate and cabin or engine warm-up can take longer in cold weather. Follow any hybrid-system warning that calls for stopping.