P0599 on BMW: How to Diagnose & Fix
Thermostat Heater Control Circuit High
1 BMW model · 1 documented issue · $500-$1,200 repair
P0599 on BMW by model: symptoms, diagnosis and fix
The F48 X1 commonly develops coolant leaks from the electric water pump and thermostat housing. The electric water pump (auxiliary pump) is a wear item that typically fails between 60,000-100,000 miles. The thermostat housing develops cracks or seal failures, causing coolant leaks. Symptoms include coolant loss, low coolant warnings, and visible leaks. The electric water pump is critical for preventing overheating when the engine is off or during cold starts. This is a common issue across many BMW models with B-series engines.
Common Symptoms
- Low coolant warning on dashboard
- Visible coolant leak under vehicle
- Overheating warning or temperature gauge rising
- Sweet smell (coolant) from engine bay
- White smoke from exhaust (severe leak)
- Heater not working properly
How to Fix
Replace failed water pump or thermostat housing. Electric water pump replacement is 2-3 hours labor. Thermostat housing is 1-2 hours. Always use BMW-approved coolant (blue or orange, do not mix). Properly bleed cooling system after repair to prevent air pockets. Inspect all coolant hoses during repair and replace if cracked. Preventive replacement of water pump at 80,000 miles recommended.
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 BMW?
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 BMW it is documented across 1 model: X1.
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 BMW?
Published repair estimates on BMW range from $500 to $1,200 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.