What does P0598 mean?
The thermostat heater control circuit voltage is lower than expected.
Quick Decision Guide
- Low coolant
- Faulty cooling fan relay
- Blown fuse
When to stop driving
Stop driving immediately if the temperature gauge rises, steam appears, coolant leaks heavily, or an overheat warning appears.
Reviewed by ratchit Automotive Solutions for clarity and inspection-first safety framing. Not a substitute for professional diagnosis.
Repair Decision & Cost Guide
Use this guide to decide what to inspect first, what it may cost, and when to move from DIY checks to professional diagnosis.
P0598 affects warm-up performance — confirm the actual coolant temperature with a scanner before replacing the thermostat or sensor.
DIY vs. Shop
Can you keep driving?
Best first DIY check
Don't replace this first
When to seek a shop
Recommended next action
Estimated Repair Cost
Inspection cost
$0–$25 DIY scanner
Shop diagnostic cost
$80–$150 (typical shop diagnostic fee)
Shop repair cost
$80–$900
Diagnostic uncertainty: This code points to a system or condition, not a guaranteed failed part. Inspect before replacing.
Cost variation: Costs vary by vehicle, location, part quality, labor rate, and the confirmed root cause.
Inspect Before Replacing
These checks are cheap, fast, and rule out the most common causes before spending money on parts.
- 1Check coolant level only when the engine is cool.
- 2Watch the temperature gauge and stop driving if the engine overheats.
Track this cooling issue
Save this issue to My Garage, track what you inspect, and build service history for this vehicle.
V-IQ readiness preview: Medium impact — resolving and tracking this issue may improve your V-IQ readiness. Tracking active codes and resolutions builds a service history we use to estimate V-IQ readiness over time.
Understanding P0598 in detail
P0598 indicates the engine computer detected a problem in the cooling control system. Depending on the code, this may involve the cooling fan circuit, thermostat heater circuit, coolant temperature behavior, or related wiring. Cooling faults can affect warm-up time, fuel economy, emissions readiness, and overheat protection. Check coolant level, fan operation, fuses, relays, wiring, and live coolant temperature data before replacing the thermostat, fan assembly, or sensor.
Symptoms of P0598
- Check engine light
- Engine runs hot
- Cooling fan not running
- Cooling fan runs constantly
- Poor heater performance
- Slow warm-up
- Failed emissions readiness
Common causes
- Low coolant
- Faulty cooling fan relay
- Blown fuse
- Damaged fan wiring
- Faulty thermostat/heater circuit
- Coolant temperature sensor issue
How to diagnose P0598
Steps ordered by urgency — tackle Now items first.
- NowCheck coolant level only when the engine is cool.
- NowWatch the temperature gauge and stop driving if the engine overheats.
- SoonCheck fuses, relays, and fan operation with the A/C commanded on.
- SoonCompare live coolant temperature data to actual engine temperature.
- LaterTest thermostat heater or fan control circuits before replacing major parts.
How to fix P0598
Fixes listed in order of likelihood and cost-efficiency.
- 1Top off/repair coolant leak
- 2Replace fan relay or fuse
- 3Repair cooling fan wiring
- 4Replace cooling fan assembly
- 5Replace thermostat or thermostat heater
- 6Replace coolant temperature sensor
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Recommended tools & parts
These recommendations appear because this issue commonly requires inspection in this system area. ratchit does not recommend replacing parts until the likely cause is confirmed.
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Estimated Repair Cost — P0598
Ranges vary by vehicle, region, and shop. Use as a ballpark — always get a quote.
DIY estimate
$5 – $60
Shop estimate
$80 – $220
DIY estimate
$30 – $180
Shop estimate
$200 – $600
DIY estimate
$80 – $350
Shop estimate
$350 – $900
Cost data is estimated and may not reflect your specific vehicle or location.
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Frequently Asked Questions
Track this cooling issue — track what you inspect and build service history for this vehicle.
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