AutoCodes – Lexus – P0AA1 Lexus

P0AA1 Lexus Code - Hybrid Battery Positive Contactor Circuit Stuck Closed

Quick Answer

The SMRs (System Main Relays) connect and disconnect the high-voltage power supply circuit in accordance with requests from the HV control ECU. Common causes include Faulty System Main Relay, System Main Relay harness is open or shorted, System Main Relay 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: P0AA1 Lexus indicates Hybrid Battery Positive Contactor Circuit Stuck Closed.
Common causes: Common causes include Faulty System Main Relay, System Main Relay harness is open or shorted, System Main Relay 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 4,132

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
FAQs
Comments
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Code P0AA1 Lexus Description

The SMRs (System Main Relays) connect and disconnect the high-voltage power supply circuit in accordance with requests from the HV control ECU. To ensure a reliable operation, they consists of a total of 3 relays (1 for the negative side and 2 for the positive side).
To connect, SMR1 and SMR3 turn ON initially. Then, SMR2 turns ON and SMR1 turns OFF. This process protects the circuit from the high-voltage surge current by allowing the limit current to flow via the resistor. To disconnect, SMR2 and SMR3 turn OFF in that order. The HV control ECU checks that the relays have turned OFF properly.
The HV control ECU monitors the proper operation of the SMRs (CON1, CON2 and CON3) to check for a malfunction.

OBDII Code P0AA1 Lexus - Hybrid Battery Positive Contactor Circuit Stuck Closed - AutoCodes.com — P0AA1 Lexus Code - Hybrid Battery Positive Contactor Circuit Stuck Closed

What does this mean?

What are the Possible Causes of the DTC P0AA1 Lexus?

Faulty System Main Relay
System Main Relay harness is open or shorted
System Main Relay circuit poor electrical connection
Faulty HV control ECU

How to Fix the DTC P0AA1 Lexus?

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 P0AA1 Lexus 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 P0AA1 Lexus code?

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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.

Frequently Asked Questions about P0AA1 Lexus Code

1. What does the OBDII code P0AA1 mean on a Lexus?

The P0AA1 code indicates that the hybrid battery positive contactor circuit is stuck closed, preventing proper control of the high-voltage battery's power flow.

2. What are the common symptoms of the P0AA1 code on a Lexus?

Symptoms include the illumination of the check engine light, hybrid system warning light, reduced vehicle performance, and possible failure to start.

3. What causes the P0AA1 code on a Lexus?

Common causes include a malfunctioning hybrid battery contactor, damaged wiring or connectors in the contactor circuit, or a fault in the hybrid control module.

4. Can I drive my Lexus with the P0AA1 code?

It is not recommended to drive with this code, as it may result in reduced performance or damage to the hybrid system.

5. How is the P0AA1 code diagnosed on a Lexus?

A technician will use a scan tool to confirm the code, check for related codes, inspect the contactor circuit wiring, and test the hybrid battery contactor for proper operation.

6. How do I fix the P0AA1 code on my Lexus?

Fixes may include replacing the hybrid battery contactor, repairing or replacing damaged wiring, or reprogramming or replacing the hybrid control module.

7. How much does it cost to repair the P0AA1 code on a Lexus?

Repair costs vary depending on the exact issue, but replacing a hybrid battery contactor can cost between $300 and $1,000, excluding labor.

8. Can a dead 12V battery cause the P0AA1 code on a Lexus?

A weak or dead 12V battery is unlikely to directly cause this code but may contribute to related issues in the hybrid system.

9. Is the P0AA1 code exclusive to Lexus vehicles?

No, the P0AA1 code can appear on other hybrid vehicles, but the specific diagnosis and repair steps may vary by make and model.

10. Can I reset the P0AA1 code without repairs?

Clearing the code without addressing the underlying issue may temporarily turn off the warning lights, but the problem will likely return and could damage the hybrid system.