P0AAF: Hybrid/EV Battery Pack Air Temperature Sensor A Circuit High

What it means

The control module detects a high signal in the hybrid battery pack air temperature sensor A circuit.

At a glance

• Usually lights the check-engine light
• The engine or gearbox may go into limp mode

How it works

Battery-pack air temperature sensor A provides the control module with a temperature signal for air around the hybrid or EV battery. This code sets when that signal is higher than expected, which can happen if the circuit is open or the sensor cannot pull the signal into its normal range.

Common causes

Most likely first.

1. Open signal wire or circuit
2. Failed sensor
3. Wiring or connector fault

Symptoms

• Hybrid system warning light

How to diagnose it

1. Record freeze-frame data and check sensor A’s live reading against ambient conditions and sensor B, if available, to confirm the high-signal fault.
2. With the vehicle safely powered down according to manufacturer instructions, inspect sensor A’s connector and wiring for a disconnected plug, corrosion, broken conductors, or damaged insulation.
3. Check sensor A’s signal circuit for an open and verify its connector and ground connections using the wiring diagram.
4. Test sensor A using the manufacturer’s procedure to distinguish an internal sensor fault from an open or poor circuit connection.
5. Compare circuit and sensor test results with the manufacturer’s specifications before deciding which part or wiring needs repair.

Common fixes

• Reconnect and secure a loose sensor A connector.
• Repair an open or damaged wire in sensor A’s circuit.
• Clean or repair corroded or poor connector contacts.
• Replace sensor A if it fails the manufacturer’s tests.

Can I keep driving?

The hybrid system may limit output or cooling when sensor A’s reading is unreliable. Avoid hard acceleration and extended trips until checked, and stop if the vehicle shows overheating or a severe power reduction.