P0599 on Chevrolet: How to Diagnose & Fix
Thermostat Heater Control Circuit High
2 Chevrolet models · 2 documented issues · $150-$1,800 repair
P0599 on Chevrolet by model: symptoms, diagnosis and fix
Camaro owners report persistent overheating issues, particularly at idle, caused by cooling fan failures, faulty fan relays, clogged radiators, failing water pumps, and thermostat problems. Temperatures reaching 240-250°F have been reported.
Common Symptoms
- Temperature gauge reading above normal (240-250°F)
- Overheating primarily at idle or low speeds
- Coolant loss without visible external leaks
- Cooling fans not engaging
- Steam or coolant smell from engine bay
How to Fix
Radiator flush or replacement for clogged radiators. Cooling fan motor or relay replacement. Thermostat replacement. Water pump replacement. Coolant system pressure test to find leaks.
Sources for this issue (1)
The 2011-2016 Cruze 1.4L turbo engine has chronic coolant leaks from the water outlet housing and thermostat housing. These plastic components crack from heat cycling. The turbo coolant feed and return lines also develop leaks at the crimped rubber-to-metal connections. Some owners report replacing the water outlet multiple times.
Common Symptoms
- Coolant puddle under vehicle
- Low coolant warning light
- Overheating in traffic
- Sweet coolant smell from engine bay
- Visible coolant residue on water outlet or thermostat housing
How to Fix
Sources for this issue (1)
P0599 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0599 mean on a Chevrolet?
P0599 stands for "Thermostat Heater Control Circuit High." This code relates to the engine cooling system's thermostat heater control circuit, used on engines with an electrically heated (map-controlled) thermostat that the computer can open early to fine-tune coolant temperature. The 'high' designation means the computer detected the control circuit voltage was higher than expected, indicating an electrical fault such as a short to voltage or an open circuit. It is generally an electrical/wiring problem rather than a mechanical cooling failure. It can affect how precisely the engine manages its operating temperature and fuel economy. On Chevrolet it is documented across 2 models: Camaro, Cruze.
What are the most common causes of P0599?
The most common causes of P0599 are: Faulty electronically heated thermostat element/heater, Short to voltage in the heater control circuit, Open or damaged wiring/connector, Corroded or loose connector at the thermostat, Poor electrical ground, Faulty PCM/ECM driver (less common). The specific cause varies by vehicle.
How much does it cost to fix P0599 on a Chevrolet?
Published repair estimates on Chevrolet range from $150 to $1,800 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0599 on a different make?
View P0599 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.