Open or high-resistance wiring in the sensor A circuit; Failed battery pack air temperature sensor A; Corroded or loose electrical connector at the sensor or control module; Short to voltage on the sensor signal circuit; Faulty battery energy control module or hybrid control module; Physical damage to the sensor or its wiring harness from debris or heat

DTC codes / P0Axx · Hybrid propulsion / P0AAF

P0AAFHybrid/EV Battery Pack Air Temperature Sensor A Circuit High

P0AAF indicates that the hybrid or electric vehicle battery pack air temperature sensor A circuit is reporting a voltage higher than the manufacturer's expected range. The battery energy control module sets this code when the sensor signal voltage exceeds the normal threshold, which typically means the circuit is open, shorted to voltage, or the sensor has failed.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaHybrid propulsion

Symptoms you may notice

Illumination of the check engine light or hybrid system warning light
Often no symptoms besides the warning light
Reduced hybrid system performance or forced limp mode
Battery cooling fan may run continuously or not at all
Possible reduction in electric-only driving range
In rare cases, the vehicle may refuse to start or enter ready mode

Common causes, most likely first

Open or high-resistance wiring in the sensor A circuit
Failed battery pack air temperature sensor A
Corroded or loose electrical connector at the sensor or control module
Short to voltage on the sensor signal circuit
Faulty battery energy control module or hybrid control module
Physical damage to the sensor or its wiring harness from debris or heat

How to diagnose and fix it

Use a scan tool to verify P0AAF is current and check for related codes in the hybrid control module
Inspect the sensor connector and wiring for corrosion, damage, or loose pins
Measure the sensor resistance and compare it to the manufacturer's temperature-resistance chart
Backprobe the sensor signal circuit to check for an open or short to voltage
Check the reference voltage and ground circuits at the sensor connector
Replace the battery pack air temperature sensor if resistance is out of specification
Clear codes and perform a road test to confirm the repair

What the battery air sensor code hides

A common oversight is assuming the sensor itself is faulty when the real problem is a chafed wire harness near the battery pack, which can cause an intermittent open circuit.
The code can be set by a poor connection at the hybrid control module even when the sensor and wiring test good, so always check both ends of the circuit.
Some vehicles use multiple battery air temperature sensors, and a high-voltage code for sensor A does not automatically mean the others are fine, so inspect all related sensors.
A weak or failing 12-volt auxiliary battery can cause erratic sensor readings and set this code on some hybrids, so load-test the battery before condemning the sensor.
After replacing the sensor, the hybrid control module may require a relearn or calibration procedure, and skipping it can leave the code stored or cause poor battery cooling performance.

Can I keep driving with P0AAF?

You can usually drive the vehicle short distances to a repair shop, but avoid heavy acceleration or long trips because the battery pack may not cool properly. If the hybrid system warning light is on or the vehicle enters limp mode, stop driving and have it towed to prevent battery damage.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.