AutoCodes – Generic – B0509

B0509 Code - Output Air Temperature Sensor 3 Circuit

Quick Answer

Air temperature sensors allow the Heating, Ventilation, and Air Conditioning (HVAC) Control Module to monitor the temperature of the discharge air in the HVAC ducts. Common causes include Faulty Output Air Temperature Sensor 3, Output Air Temperature Sensor 3 harness is open or shorted, Output Air Temperature Sensor 3 circuit poor electrical connection. Severity is Low - monitor the vehicle and repair when practical. The vehicle can usually be driven if no severe symptoms are present, but symptoms should be checked before extended driving.

What it means: B0509 indicates Output Air Temperature Sensor 3 Circuit.
Common causes: Common causes include Faulty Output Air Temperature Sensor 3, Output Air Temperature Sensor 3 harness is open or shorted, Output Air Temperature Sensor 3 circuit poor electrical connection.
Severity: Low - monitor the vehicle and repair when practical.
Can I drive?: The vehicle can usually be driven if no severe symptoms are present, but symptoms should be checked before extended driving.

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Code Popularity 918

How popular is this code, among other codes? Low

Repair Importance Level

Low (Monitor) (1 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Mar 11, 2021

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code B0509 Description

Air temperature sensors allow the Heating, Ventilation, and Air Conditioning (HVAC) Control Module to monitor the temperature of the discharge air in the HVAC ducts. The module applies 5 volts to internal input resistors that are connected to the signal circuits of the air temperature sensors. The module provides ground to the air temperature sensors through the low reference circuit. The HVAC control module monitors the voltage drops across the air temperature sensors and uses the inputs for automatic control calculations. When the duct air temperatures are cold, the resistances of the sensors are high and the voltage signals are high. When the duct air temperatures are hot, the resistances of the sensors are low and the voltage signals are low. The HVAC control module converts the voltage values to count values where 1 volt is approximately equal to 51 counts.

OBDII Code B0509 - Output Air Temperature Sensor 3 Circuit - AutoCodes.com — B0509 Code - Output Air Temperature Sensor 3 Circuit

What does this mean?

What are the Possible Causes of the DTC B0509?

Faulty Output Air Temperature Sensor 3
Output Air Temperature Sensor 3 harness is open or shorted
Output Air Temperature Sensor 3 circuit poor electrical connection
Faulty Heating, Ventilation, and Air Conditioning (HVAC) Control Module

How to Fix the DTC B0509?

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 does this mean?

Code Tech Notes

B0509 05: Output Air Temperature Sensor 3 Circuit Short to Battery or Open
B0509 02: Output Air Temperature Sensor 3 Circuit Short to Ground

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the B0509 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 B0509 code?

Need more information on how to fix the B0509 code? Get Access to Factory Service Manuals

Need Help with the Code?

Get the B0509 code diagnosed by a professional: Find a repair shop in your area

Information for Specific Makes

B0509 Buick — Output Air Temperature Sensor 3 Circuit
B0509 Cadillac — Output Air Temperature Sensor 3 Circuit
B0509 Chevrolet — Output Air Temperature Sensor 3 Circuit
B0509 GMC — Output Air Temperature Sensor 3 Circuit

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 B0509 Code

1. What are the common symptoms of OBDII code B0509 (Output Air Temperature Sensor 3 Circuit)?

- Common symptoms include poor engine performance, rough idling, decreased fuel efficiency, and potential issues with the vehicle's HVAC system.

2. What are the possible causes of OBDII code B0509?

- The code B0509 can be triggered by a faulty output air temperature sensor, damaged wiring or connectors related to the sensor, or issues with the sensor circuit.

3. How can I diagnose the cause of OBDII code B0509?

- To diagnose the issue, you can use an OBDII scanner to retrieve the specific error code and then inspect the output air temperature sensor, its wiring, and connectors for any visible damage or issues.

4. Is it safe to continue driving with OBDII code B0509 present?

- It is not recommended to continue driving with the B0509 code as it can lead to further engine and performance issues. It is best to address the problem promptly.

5. How can I repair OBDII code B0509?

- Repairing the B0509 code may involve replacing the output air temperature sensor, repairing or replacing damaged wiring or connectors, or resetting the sensor circuit as needed.

6. Can I reset the OBDII code B0509 on my own?

- You can attempt to reset the B0509 code using an OBDII scanner or by disconnecting the vehicle's battery for a few minutes. However, it is important to address the underlying issue causing the code to prevent it from recurring.

7. How much does it typically cost to fix OBDII code B0509?

- The cost of fixing OBDII code B0509 can vary depending on the specific cause of the issue, the labor rates of the repair shop, and the cost of any parts that may need to be replaced. It is advisable to get a diagnostic assessment for an accurate estimate.

8. Can a DIY enthusiast fix OBDII code B0509 at home?

- Depending on the individual's skill level and access to tools, some DIY enthusiasts may be able to address OBDII code B0509 at home by following repair guides or tutorials. However, it is important to ensure the repair is done correctly to avoid further damage.

9. How long does it take to repair OBDII code B0509?

- The repair time for OBDII code B0509 can vary based on the specific cause of the issue and the complexity of the repair needed. It can range from a quick sensor replacement to a more involved wiring repair.

10. Will OBDII code B0509 cause my vehicle to fail an emissions test?

- The B0509 code may affect your vehicle's emissions output, potentially leading to a failed emissions test. It is advisable to address the issue promptly to ensure your vehicle meets emission standards.