AutoCodes – Generic – P0A91

P0A91 Code - Drive Motor 'B' Performance

Quick Answer

The HV transaxle consists of a planetary gear unit, MG1 and MG2. Common causes include Faulty Engine assembly, Faulty HV transaxle assembly (shaft or gear), Faulty Transmission input damper. 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: P0A91 indicates Drive Motor 'B' Performance.
Common causes: Common causes include Faulty Engine assembly, Faulty HV transaxle assembly (shaft or gear), Faulty Transmission input damper.
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 6,905

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 May 11, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
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Code P0A91 Description

The HV transaxle consists of a planetary gear unit, MG1 and MG2.
A gear unit uses the planetary gear to split engine output in accordance with a driving request during driving the vehicle or charging its internal HV battery.
The MG2 provides assistance to the engine output while increasing the drive force of the vehicle.
Furthermore, the MG2 effects regenerative braking by converting the energy (which is consumed in the form of heat during normal braking) into electrical energy and recovering it into the HV battery. Through regenerative braking, as well as decelerating the vehicle, the MG2 generates high-voltage electrical power which is used for the purpose of charging the HV battery.
The MG1 supplies electrical power, which is used for charging the HV battery or for driving the MG2. It also has a stepless transmission function to control the transaxle by regulating the amount of generation of electrical energy, which effectively varies the MG1 speed. In addition, the MG1 is used as a starter motor to start the engine.
The transmission input damper absorbs the shock that accompanies transmission of the drive force from the engine.

OBDII Code P0A91 - Drive Motor 'B' Performance - AutoCodes.com — P0A91 Code - Drive Motor 'B' Performance

What does this mean?

What are the Possible Causes of the DTC P0A91?

Faulty Engine assembly
Faulty HV transaxle assembly (shaft or gear)
Faulty Transmission input damper
Wire harness or connector
HV control ECU

How to Fix the DTC P0A91?

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 P0A91 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.

Need more information about the P0A91 code?

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Information for Specific Makes

P0A91 Lexus — Drive Motor 'B' Performance
P0A91 Nissan — Drive Motor 'B' Performance
P0A91 Toyota — Drive Motor 'B' Performance

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.