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P0599 Audi Code - Thermostat Heater Control Circuit High

Quick Answer

The P0599 Audi OBD-II trouble code refers to an issue with the thermostat heater control circuit being detected as high. Common causes include Faulty thermostat heater control circuit: A malfunction in the circuit itself can trigger this trouble code, Defective thermostat: If the thermostat is not working correctly, it can cause issues with the heater control circuit, Wiring issues: Damage or corrosion in the wiring connected to the thermostat heater can disrupt the circuit's operation. 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
P0599 Audi indicates Thermostat Heater Control Circuit High.
Common causes
Common causes include Faulty thermostat heater control circuit: A malfunction in the circuit itself can trigger this trouble code, Defective thermostat: If the thermostat is not working correctly, it can cause issues with the heater control circuit, Wiring issues: Damage or corrosion in the wiring connected to the thermostat heater can disrupt the circuit's operation.
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.
What is this?
Table of contents Created and updated by William Orellana on Sep 08, 2024
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Code P0599 Audi Description

The P0599 Audi OBD-II trouble code refers to an issue with the thermostat heater control circuit being detected as high. The thermostat in a vehicle is responsible for regulating the engine's temperature by controlling the flow of coolant through the engine. The thermostat heater control circuit is a component that helps to warm up the thermostat quickly to reach the optimal operating temperature more efficiently. When this circuit is detected as high, it means that there is an electrical fault in the system, causing the thermostat heater to operate at a higher than normal voltage level.

OBDII Code P0599 Audi - Thermostat Heater Control Circuit High
P0599 Audi Code - Thermostat Heater Control Circuit High

Common Causes of P0599 Audi

  1. Faulty thermostat heater control circuit: A malfunction in the circuit itself can trigger this trouble code.
  2. Defective thermostat: If the thermostat is not working correctly, it can cause issues with the heater control circuit.
  3. Wiring issues: Damage or corrosion in the wiring connected to the thermostat heater can disrupt the circuit's operation.
  4. Engine control module (ECM) failure: A malfunction in the ECM can also lead to the thermostat heater control circuit high code.

Symptoms of P0599 Audi

  1. Engine overheating: One of the most common symptoms associated with this code is the engine overheating due to the thermostat not functioning properly.
  2. Poor fuel efficiency: The engine may run inefficiently, leading to increased fuel consumption.
  3. Check engine light: The vehicle's onboard diagnostic system may trigger the check engine light to alert the driver to a problem.
  4. Engine misfires: The engine may misfire or run rough due to the incorrect engine temperature.

How to Fix P0599 Audi

  1. Diagnose the issue: Use an OBD-II scanner to read the trouble code and pinpoint the exact cause of the problem.
  2. Inspect the thermostat heater control circuit: Check the wiring and connections for any signs of damage or corrosion.
  3. Test the thermostat: Verify if the thermostat is functioning correctly and replace it if necessary.
  4. Repair or replace faulty components: Address any issues found with the thermostat heater control circuit, wiring, or ECM.
  5. Clear the trouble code: Once the repairs are completed, clear the trouble code from the vehicle's memory using the OBD-II scanner.

Cost to Fix P0599 Audi

The typical repair costs for addressing a P0599 Audi trouble code can range from $200 to $500, depending on the specific cause of the issue and the parts and labor required for the repair. It's important to note that the actual cost can vary based on factors such as the vehicle's make and model, the location of the repair shop, and the extent of the repairs needed. Additionally, the diagnosis time and labor rates at auto repair shops can vary, with rates typically ranging between $80 and $150 per hour. It's advisable to inquire with local repair shops for a more precise estimate based on your specific circumstances.

What does this mean?

Tech Notes for P0599 Audi

If there are no coolant system leaks, replace the thermostat to fix the problem.

When is the Code Detected?

The P0598 is triggered when there is an open or short thermostat heather control circuit.

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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 P0599 Audi Code

1. What does the OBDII code P0599 mean on an Audi?

P0599 indicates a high voltage issue in the thermostat heater control circuit, which is responsible for regulating the engine's operating temperature.

2. What are the symptoms of a P0599 code on an Audi?

Symptoms may include an illuminated check engine light, poor fuel efficiency, engine overheating, or the engine taking too long to reach operating temperature.

3. What causes the P0599 code on an Audi?

Common causes include a faulty thermostat heater, damaged wiring or connectors in the thermostat control circuit, a failed coolant temperature sensor, or a malfunctioning engine control module (ECM).

4. Can I drive my Audi with a P0599 code?

While the vehicle may still run, driving with this code can lead to engine overheating or inefficient engine performance, potentially causing further damage over time.

5. How is the P0599 code diagnosed on an Audi?

A mechanic will typically use an OBDII scanner to confirm the code, inspect the thermostat heater and wiring, and test the voltage and resistance of the thermostat control circuit.

6. How do you fix a P0599 code on an Audi?

Repairs may involve replacing the thermostat assembly, repairing damaged wiring or connectors, or in rare cases, replacing the ECM.

7. How much does it cost to fix a P0599 code on an Audi?

The cost varies depending on the issue, but replacing the thermostat typically costs between $200 and $500, including parts and labor.

8. Can a P0599 code be caused by low coolant levels?

Low coolant levels are unlikely to directly cause this code but can lead to overheating, which may indirectly affect the thermostat’s operation.

9. Does clearing the P0599 code fix the problem?

Clearing the code will temporarily turn off the check engine light, but the underlying issue must be addressed to prevent the code from returning.

10. How can I prevent the P0599 code from occurring again?

Regular maintenance, including checking coolant levels and inspecting wiring for damage, can help prevent issues with the thermostat heater control circuit.

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