P0598 code meaning
Thermostat Heater Control Circuit Low
Powertrain system Generic code P05xx codes Check engine light
What P0598 means
A map-controlled thermostat is a wax thermostat with a built-in heating resistor (Valeo: about 10 Ω). Unheated it opens late, for hot running at part load; the engine module heats it by map under full load or towing so it opens earlier. CARB requires the thermostat to be monitored and the heater circuit counts as an output component. GM switches it to ground with a low-side driver and checks it every second, fault after 15 of 30 samples, type B; Hyundai/Kia/Genesis and VW/Audi use the codes as well. P0598 means the control line is shorted to ground – GM detects 0.5 Ω with the driver off. With a low-side driver the heater then stays on permanently and the thermostat opens early, so the engine runs cool; Kia's Cadenza bulletins list it with P0128 and replace the thermostat.
P0598 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor1 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P0598
- Check engine light on
- Engine slow to reach operating temperature (possibly P0128)
- Weak cabin heating in winter, higher consumption
Common causes of P0598
- Most likelyInternal short in thermostat or heater, coolant in the connector
- PossibleControl line shorted to ground (chafing)
- Less likelyEngine module driver
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
MAP controlled thermostatThermostat heaterHeater wiringEngine control module
What each part of P0598 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 5 | Area: vehicle speed, idle control and auxiliary inputs. |
| 98 | The exact fault in that area. |
What to do next
- Note P0598 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0598
What does P0598 mean?
P0598 means "Thermostat Heater Control Circuit Low". A map-controlled thermostat is a wax thermostat with a built-in heating resistor (Valeo: about 10 Ω). It is a generic code, so it means the same on every make.
Is it safe to drive with P0598?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P0598 fail an emissions test?
Yes, it can. P0598 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0598 to fix?
Difficulty: medium. A typical repair takes 1 to 3 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0598 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.