P0599 Fault Code

Thermostat Heater Control Circuit High

• What does that mean?
• Symptoms
• Causes
• Solutions

The P0599 fault code indicates a problem with the thermostat heater control circuit, specifically that the circuit is reading too high. This usually affects the engine's ability to maintain the optimal operating temperature, which can lead to increased emissions and reduced fuel efficiency.

What are the symptoms of the P0599 code?

You may notice several symptoms when dealing with a P0599 code:

• Check Engine Light illuminated on the dashboard
• Engine overheating or running too cold
• Poor fuel economy
• Unusual engine behavior or performance issues
• Increased emissions during vehicle operation.

What causes the P0599 code?

Common causes for the P0599 code include:

• Faulty thermostat
• Short circuit or wiring issues in the thermostat heater control circuit
• Malfunctioning Engine Control Module (ECM)
• Poor connections or corroded terminals in the thermostat circuit.

How to fix P0599?

To resolve the P0599 fault code, consider the following actions:

• Inspect the thermostat for proper operation and replace if necessary.
• Check the wiring and connectors in the thermostat heater control circuit for any signs of damage or corrosion.
• Test the Engine Control Module (ECM) to ensure it’s functioning correctly.
• Clear the fault code and monitor if it reappears after repairs.