P0597 on Chevrolet: How to Diagnose & Fix
Thermostat Heater Control Circuit Open
2 Chevrolet models · 2 documented issues · $150-$1,800 repair
P0597 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 Sonic uses a molded plastic thermostat housing (coolant outlet) on both the 1.8L LUW/LWE and 1.4L turbo engines. Repeated thermal cycling embrittles the plastic, and the housing cracks at the seams, at the hose-neck stubs, or the integrated O-ring seal takes a set. Coolant weeps down onto the transmission bell housing and the block, so owners often mistake it for a transmission or oil leak. Because the thermostat is integral to the housing, a stuck-open thermostat frequently accompanies the leak, producing slow warm-up and poor heater output. Sonic Owners Forum members list the coolant outlet alongside the surge tank and plastic coolant elbows as a cluster of thermal-fatigue failures that show up on higher-mileage cars. This is a separate component from the water pump, which has its own well-known failure.
Common Symptoms
- Orange/pink coolant dripping onto the transmission or under the front of the engine
- Sweet coolant smell after driving
- Coolant reservoir level dropping with no visible puddle at first
- Temperature gauge reading low or heater blowing cool
- Engine overheating in severe cases
- Check engine light
How to Fix
Pressure-test the cooling system cold to confirm the source before parts are thrown at it. If the housing body is intact, replacing the thermostat/housing seal is sometimes enough, but most shops replace the complete housing assembly with a new thermostat since the two are integrated. Clean the mating surface on the head, torque the fasteners to spec (roughly 89 in-lb - they strip easily), then refill and bleed the system properly to purge air pockets. Several owners upgrade to an aluminum aftermarket housing to avoid a repeat failure. Inspect the plastic coolant elbows and T-fittings at the rear of the engine at the same time, as they fail from the same cause.
Sources for this issue (3)
P0597 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 P0597 mean on a Chevrolet?
P0597 stands for "Thermostat Heater Control Circuit Open." P0597 is a cooling-system code indicating an open electrical circuit in the control for the heated (electronically controlled) engine thermostat. Many modern engines use a thermostat with a built-in heater element that the computer can energize to open the thermostat sooner for better temperature management and emissions. When the PCM commands that heater but detects no electrical continuity (an open circuit), it sets this code. It generally means the thermostat heater isn't being controlled, which can affect coolant temperature regulation, fuel economy, and emissions. On Chevrolet it is documented across 2 models: Camaro, Sonic.
What are the most common causes of P0597?
The most common causes of P0597 are: Failed thermostat heater element or integrated control thermostat, Open or broken wiring to the thermostat heater circuit, Corroded, loose, or disconnected thermostat connector, Blown fuse or open in the heater power feed, Poor ground or control-circuit fault from the PCM, Damaged PCM driver for the heater (rare). The specific cause varies by vehicle.
How much does it cost to fix P0597 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 P0597 on a different make?
View P0597 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.