Engine-CodesCadillac – P0599 Cadillac

P0599 Cadillac Code - Thermostat Heater Control Circuit High

Quick Answer

The P0599 diagnostic trouble code (DTC) for Cadillac vehicles refers to the thermostat heater control circuit being high. Common causes include Faulty thermostat heater, Wiring issues such as shorts or open circuits, Faulty Engine Control Module (ECM). 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 Cadillac indicates Thermostat Heater Control Circuit High.
Common causes
Common causes include Faulty thermostat heater, Wiring issues such as shorts or open circuits, Faulty Engine Control Module (ECM).
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.
Table of contents Created and updated by William Orellana on Aug 25, 2024
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Code P0599 Cadillac Description

The P0599 diagnostic trouble code (DTC) for Cadillac vehicles refers to the thermostat heater control circuit being high. This code typically indicates an issue with the thermostat heater control circuit, which is responsible for regulating the temperature of the engine coolant. The thermostat heater control circuit is an essential component of the engine cooling system, ensuring that the engine operates within the optimal temperature range.

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

Common Causes of P0599 Cadillac

  1. Faulty thermostat heater
  2. Wiring issues such as shorts or open circuits
  3. Faulty Engine Control Module (ECM)
  4. Corrosion or damage to electrical connections
  5. Coolant leaks affecting the thermostat

Symptoms of P0599 Cadillac

  1. Engine overheating
  2. Poor fuel economy
  3. Rough idling or stalling
  4. Check Engine Light illuminated
  5. Inaccurate temperature gauge readings

How to Fix P0599 Cadillac

  1. Begin by diagnosing the root cause of the issue using a diagnostic scanner to confirm the P0599 code.
  2. Inspect the thermostat heater and wiring for any visible signs of damage or corrosion.
  3. Test the thermostat heater control circuit for proper voltage and resistance.
  4. Replace the thermostat heater if it is found to be faulty, and repair any damaged wiring or connections.
  5. Clear the DTC and test drive the vehicle to ensure the issue has been resolved.

Cost to Fix P0599 Cadillac

The cost of repairing a P0599 code can vary depending on the underlying cause of the issue. In general, replacing a faulty thermostat heater or repairing wiring issues may cost between $150 to $400, including parts and labor. However, it's important to note that labor rates can vary significantly between different auto repair shops, so it's advisable to obtain multiple quotes for a more accurate estimate. Additionally, the cost may increase if other components need to be replaced or if further diagnostics are required.

Tech Notes for P0599 Cadillac

The engine coolant thermostat heater has a mechanical fail-safe in case of an electrical condition with the engine coolant thermostat heater. The mechanical thermostat will open at approximately 104°C (220°F). The mechanical thermostat will cycle from approximately 104°C (220°F) to approximately 98°C (208°F). The heater is part of the thermostat. The engine coolant thermostat heater and the thermostat housing are serviced as an assembly.

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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.

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