P0598 on Audi
Thermostat Heater Control Circuit Low
P0598 on Audi vehicles indicates thermostat heater control circuit low. Au7o has documented this code across 4 Audi models — most commonly on A4, A7, Q5. This code applies to engines with an electronically controlled (heated) thermostat and means the Powertrain Control Module detected an abnormally low voltage in the thermostat heater control circuit. The heater element lets the computer fine-tune coolant temperature for efficiency and emissions by opening the thermostat sooner under certain conditions. P0598 sets when the control or feedback circuit reads lower than expected (often a short to ground or loss of supply). It is found mainly on certain European makes (BMW, Mercedes, VW/Audi, etc.) and usually has little effect on driving. Typical repair costs on Audi range from $150 to $5,000, depending on the specific model and root cause.
Common Causes of P0598
- •Faulty electronically controlled (map-controlled) thermostat
- •Short to ground in the heater control wiring
- •Corroded or loose thermostat connector
- •Open or damaged wiring in the control circuit
- •Low coolant level overheating the thermostat heater
- •Blown fuse or poor power supply to the circuit
- •Faulty PCM control driver
P0598 on Audi by Model
Audi A4(1 issue)
- Water Pump/Thermostat Failure2009-2020
The plastic water pump housing and thermostat are known failure points on Audi 2.0T engines. Leaks and failures typically occur between 60,000-100,000 miles. The plastic components crack from heat cycling.
Audi A7(1 issue)
- Thermostat Housing Coolant Leak2012-2018
The 3.0T V6 thermostat housing in the C7 A7 develops coolant leaks from the plastic housing and its O-ring seals. The housing is located at the front of the engine and cracks or warps over thermal cycling. Coolant leaks onto the serpentine belt area and can cause belt slippage or overheating if coolant loss is significant.
Audi Q5(1 issue)
- Coolant Leaks (Thermostat Housing and Hoses)2009-2017
Audi Q5 (2009-2017) experiences coolant leaks from thermostat housing, coolant flanges, and hoses. Plastic components crack with age/heat cycles, causing leaks. Symptoms include coolant smell, visible leaks under vehicle, low coolant warning, and overheating. If leaks ignored, engine overheats causing severe damage. Common leak points: thermostat housing, upper coolant flange, lower coolant flange, heater core hoses.
Audi Q7(1 issue)
- Water Pump and Thermostat Failure (Overheating)2007-2015
The 2007-2015 Audi Q7 (3.0T, 3.6L, TDI) experiences water pump and thermostat failures causing engine overheating. Plastic impeller water pumps fail from debris clogging or electronic failures. When pump fails, coolant flow drops causing rapid overheating and severe engine damage (warped cylinder heads, blown gaskets). Thermostat housings crack and leak coolant. Failure often occurs around 60k-80k miles. Preventive replacement recommended.
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View P0598 across all makes →Frequently Asked Questions
What does P0598 mean on Audi?▼
P0598 stands for "Thermostat Heater Control Circuit Low." This code applies to engines with an electronically controlled (heated) thermostat and means the Powertrain Control Module detected an abnormally low voltage in the thermostat heater control circuit. The heater element lets the computer fine-tune coolant temperature for efficiency and emissions by opening the thermostat sooner under certain conditions. P0598 sets when the control or feedback circuit reads lower than expected (often a short to ground or loss of supply). It is found mainly on certain European makes (BMW, Mercedes, VW/Audi, etc.) and usually has little effect on driving. On Audi specifically, this code is documented across 4 models.
What causes P0598 on Audi vehicles?▼
Common causes on Audi: Faulty electronically controlled (map-controlled) thermostat, Short to ground in the heater control wiring, Corroded or loose thermostat connector, Open or damaged wiring in the control circuit, Low coolant level overheating the thermostat heater. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0598 on a Audi?▼
Repair costs on Audi range from $150 to $5,000, depending on the specific model and root cause.
Which Audi models have P0598 documented?▼
Au7o has documented P0598 on 4 Audi models: A4, A7, Q5, Q7.