P0599: Thermostat Heater Control Circuit High
17 vehicles · 8 makes · $60-$6,000 repair
P0599 is an OBD-II diagnostic trouble code meaning “Thermostat Heater Control Circuit High.” The electronically heated thermostat control circuit has excessive voltage. Applies to vehicles with electronically controlled thermostats. This code appears across 17 vehicle models from 8 manufacturers, with repair costs ranging from $60 to $6,000.
Common Causes
Typical Repair Cost
Based on 19 documented vehicle-specific issues. Actual cost depends on root cause and vehicle.
Diagnostic Tools
To diagnose P0599, you'll need an OBD-II scanner. Here are our recommendations at every price point.
ANCEL AD310 Classic OBD-II Scanner
by ANCEL
A simple, affordable code reader that reads and clears check engine codes. Great for quick diagnostics on any OBD-II vehicle (1996+).
- Read & clear engine codes
- View freeze frame data
- I/M readiness status
- No batteries or app needed
BlueDriver Pro Bluetooth Scanner
by BlueDriver
Bluetooth OBD-II scanner with a free companion app. Provides enhanced diagnostics, smog readiness, and repair reports sourced from a database of verified fixes.
- Enhanced diagnostics (ABS, SRS, transmission)
- Repair Reports with verified fixes
- Smog check readiness
- Free app (iOS & Android)
LAUNCH CRP123X OBD-II Scanner
by LAUNCH
A professional-grade handheld scanner that reads all four major systems (engine, transmission, ABS, SRS) with live data streaming and graphing.
- Engine, transmission, ABS, SRS diagnostics
- Live data stream & graphing
- AutoVIN for vehicle identification
- Free lifetime updates via Wi-Fi
Autel MaxiCOM MK808S Diagnostic Tool
by Autel
Shop-level diagnostic tablet with bi-directional control, active tests, and full system coverage. Ideal for serious DIYers and small shops.
- All-system diagnostics (25+ modules)
- Bi-directional control & active tests
- Oil reset, EPB, BMS, TPMS, injector coding
- 7-inch touchscreen with Android OS
As an Amazon Associate, we earn from qualifying purchases. Prices are approximate and may vary.
Vehicles Affected (17)
Water Pump/Thermostat Failure
Water Pump and Thermostat Failure (Overheating)
Coolant Leaks (Thermostat Housing and Hoses)
Water Pump and Thermostat Housing Failure (EA888 Gen 3)
Water Pump and Thermostat Housing Failure (2.0 TFSI)
Thermostat Housing Coolant Leak / Cracking
Engine Overheating / Water Pump and Radiator Fan Failure
Thermostat Housing Coolant Leak
Engine Overheating / Cooling System Failures
FAQ
What does P0599 mean?
P0599 stands for "Thermostat Heater Control Circuit High." The electronically heated thermostat control circuit has excessive voltage. Applies to vehicles with electronically controlled thermostats.
What are the most common causes of P0599?
The most common causes of P0599 are: Failed heated thermostat, Wiring short to power, Faulty thermostat control module, Corroded connector, ECU fault. The specific cause varies by vehicle.
How much does it cost to fix P0599?
Repair costs for P0599 range from $60 to $6,000, depending on the vehicle and root cause.
Which vehicles are affected by P0599?
Au7o has documented P0599 across 17 vehicle models from 8 manufacturers: Audi, BMW, Cadillac, Chevrolet, Dodge, Jeep, MINI, Mercedes-Benz.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.