P0599: Thermostat Heater Control Circuit High
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. According to Au7o's database, this code appears across 16 vehicle models from 7 manufacturers, with repair costs ranging from $60 to $6,000. Full vehicle-specific causes and solutions at au7o.io.
Common Causes
Typical Repair Cost
Range based on 18 documented vehicle-specific issues. Actual cost depends on the root cause, your vehicle, and whether you DIY or visit a shop.
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 by P0599
Click any vehicle to see the full issue details, symptoms, and repair guide.
Related Codes
Frequently Asked Questions
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 — Au7o documents vehicle-specific causes for 16 models.
How much does it cost to fix P0599?
Repair costs for P0599 range from $60 to $6,000, depending on the specific vehicle and root cause. Some fixes like cleaning a MAF sensor are under $50, while others like replacing a catalytic converter can exceed $2,000.
Which vehicles are affected by P0599?
Au7o has documented P0599 across 16 vehicle models from 7 manufacturers: Audi, BMW, Cadillac, Chevrolet, Dodge, Jeep, MINI. See the full list below for vehicle-specific causes and repair costs.
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