AutoCodes – Generic – P0AC9

P0AC9 Code - Hybrid/EV Battery Temperature Sensor 2 Circuit Erratic

Quick Answer

Hybrid/EV Battery Temperature Sensors are used to monitor the battery temperature. Common causes include Faulty Hybrid/EV Battery Assembly, Hybrid/EV Battery Assembly harness is open or shorted, Hybrid/EV Battery Assembly circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P0AC9 indicates Hybrid/EV Battery Temperature Sensor 2 Circuit Erratic.
Common causes: Common causes include Faulty Hybrid/EV Battery Assembly, Hybrid/EV Battery Assembly harness is open or shorted, Hybrid/EV Battery Assembly circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 1,814

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Mar 22, 2024

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
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Code P0AC9 Description

Hybrid/EV Battery Temperature Sensors are used to monitor the battery temperature. The non-serviceable battery temperature sensors are located within the battery sections. Two temperature sensors are located in each battery section. The temperature sensor is a variable resistor that measures the temperature of the battery cell group. The hybrid/EV interface control module supplies 5 V to the signal circuit and is a ground for the low reference circuit. The battery temperature sensor resistance changes with battery temperature. As the temperature decreases, the sensor resistance increases. As the temperature increases, the sensor resistance decreases.
Each Hybrid/EV Battery Interface Control Module communicates the temperature sensor values to the Hybrid/EV Powertrain Control Module via serial data.
The Hybrid/EV Powertrain Control Module uses the battery temperature sensors to determine the Hybrid/EV Battery Module temperature in order to control the battery cooling system operation.
The Diagnostic Trouble Code (DTC) will be set when the hybrid battery temperature sensor is intermittent or has changed by 10°C (18°F) or greater for 4 out of 5 seconds.

OBDII Code P0AC9 - Hybrid/EV Battery Temperature Sensor 2 Circuit Erratic - AutoCodes.com — P0AC9 Code - Hybrid/EV Battery Temperature Sensor 2 Circuit Erratic

What does this mean?

What are the Possible Causes of the DTC P0AC9?

Faulty Hybrid/EV Battery Assembly
Hybrid/EV Battery Assembly harness is open or shorted
Hybrid/EV Battery Assembly circuit poor electrical connection
Faulty Hybrid/EV Battery Interface Control Module

How to Fix the DTC P0AC9?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0AC9 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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Information for Specific Makes

P0AC9 Buick — Hybrid/EV Battery Temperature Sensor 2 Circuit Erratic
P0AC9 Cadillac — Hybrid/EV Battery Temperature Sensor 2 Circuit Erratic
P0AC9 Chevrolet — Hybrid/EV Battery Temperature Sensor 2 Circuit Erratic
P0AC9 GMC — Hybrid/EV Battery Temperature Sensor 2 Circuit Erratic
P0AC9 Lexus — Hybrid Battery Temperature Sensor 'B' Circuit Intermittent/Erratic
P0AC9 Toyota — Hybrid Battery Temperature Sensor 'B' Circuit Intermittent/Erratic

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.