P0AE9: Hybrid/EV Battery Temperature Sensor D Circuit Range/Performance

P0AE9 is the plausibility check for battery temperature sensor D, GM's sensor 4: its reading is compared with the other pack sensors. In GM's 2016 and 2019 tables it fails when the value is more than 25 °C away from the average of the others in 50 of 67 samples; the two-mode hybrid tables of 2011 and 2013 use more than 15 °C in 90 of 100; the eAssist table 13OBDG05C allows 8.55 °C after a long module off time; GM's 2018 table uses 20 °C for 5 s within 6.7 s. All are Type B, two trips. Volt bulletin 18-NA-342 counts P0AE9 among sensor codes that set falsely in cold weather and fixes them by reprogramming. Otherwise a drifting sensor or a real hot spot in one module is the likely cause.

High severity. Can I keep driving?If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

Symptoms

Malfunction indicator lamp after two trips
Battery Too Cold message despite mild weather (Volt)
Reduced charge and electric drive power

Most likely causes

Outdated controller software (GM Volt, bulletin 18-NA-342)
Temperature sensor D drifting out of tolerance
Genuine local temperature difference in one battery module
Increased contact resistance in the sensor circuit

What to check, in order

Start with the simplest. You can tick off each step.

Read the codes with a hybrid-compatible scanner and write down the freeze frame data
Compare the reading with other engine data while varying the engine speed.
Make sure the battery cooling air intake is clean
Check the 12 V auxiliary battery, which can also trigger warnings
Leave any high-voltage measurements to a specialized repair shop

Good to know

It can trigger limp mode.
It affects emissions.

What each character of P0AE9 means

P: Powertrain: engine and transmission
0: Generic code: same on every make
A: Hybrid or air and fuel
E9: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0AE9?

If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

What causes code P0AE9?

The most common causes are: outdated controller software (GM Volt, bulletin 18-NA-342); temperature sensor D drifting out of tolerance; genuine local temperature difference in one battery module.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.