P0598 OBD-II Trouble Code: Thermostat Heater Control Circuit Low

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P0598 is a diagnostic trouble code (DTC) for "Thermostat Heater Control Circuit Low". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

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P0598 OBD-II Trouble Code: Thermostat Heater Control Circuit Low

P0598 code definition

The P0598 code identifies a problem with the control circuit for the thermostat heater.

The P0598 code is often associated with the P0597 and P0599 codes.

What the P0598 code means

P0598 is the OBD-II generic code for a fault involving the thermostat heater control circuit. The thermostat heater is responsible for detecting the temperature of the engine and using that information to dictate the coolant flow through the engine. To ensure that this part is working correctly, the flow of power through the unit it monitored by the powertrain control module. If this voltage reading is low, the P0598 code will be stored in the OBD-II unit.

What causes the P0598 code?

The P0598 code has a number of common causes:

  • Faulty or corroded wiring around the thermostat
  • Faulty or corroded wiring between powertrain control unit and thermostat
  • Low coolant levels
  • Faulty thermostat
  • Faulty powertrain control module

What are the symptoms of the P0598 code?

When the P0598 code appears, the Check Engine light will illuminate on the dashboard after about three ignition cycles with the same occurring problem. In most instances of the P0598 code, there will be little to no change in vehicle performance.

When the thermostat fails, it will be stopped in the position that it was in during failure. This means that coolant flow through the engine will be stuck at the same level during vehicle operation. This could cause overheating or delayed warm-up time for the engine.

How does a mechanic diagnose the P0598 code?

A qualified and skilled technician with an OBD-II scanner capable of taking the factory readings from the vehicle. This scanner will not only show them the codes that were saved by the OBD-II unit, it will show the times at which the codes were stored. The technician will make note of these times and record the information before resetting the error codes and taking the vehicle for a test drive. If the error code was triggered by a consistent problem the error code should be stored again during the test drive.

Upon confirming the location of the issue, the technician will first check the coolant level in the engine. Once that is done, they will check the wiring on and around the circuitry for the thermostat heater. The wiring around the powertrain control module will also be inspected. They will use a voltmeter to measure the power going through the circuits.

Common mistakes when diagnosing the P0598 code

The actual components of the thermostat are often blamed for the P0598 code when the problem actually lies in the electronic components surrounding the unit. This can lead to costly repairs and the replacement of functioning components unnecessarily.

How serious is the P0598 code?

The P0598 code is moderately serious. While it does not have the potential to stop the engine or prevent it from starting, it does have the potential to damage the engine itself. While damage to the engine is unlikely, there is a risk of overheating associated with the P0598 error code. Whenever the engine overheats, components can be damaged. Have a technician diagnose the problem as soon as possible if the P0598 code appears.

What repairs can fix the P0598 code?

The most common repairs to address the P0598 code are as follows:

  • Repair or replace wiring harness around thermostat
  • Repair or replace thermostat heater
  • Repair or replace powertrain control module
  • Replace or replenish coolant in engine

Additional comments for consideration regarding the P0598 code

If there is a buildup of corrosion or other engine residue on the thermostat, then a mixture of water and baking soda can be used to clean it off.

Need help with a P0598 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

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