AutoCodes – Cadillac – P0597 Cadillac

P0597 Cadillac Code - Thermostat Heater Control Circuit Open

Quick Answer

The Engine Control Module (ECM) controls the Pulse Width Modulated (PWM) thermostat. Common causes include Failed Engine Cooling Thermostat Heater, Engine Cooling Thermostat Heater harness is open or shorted, Engine Cooling Thermostat Heater circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P0597 Cadillac indicates Thermostat Heater Control Circuit Open.
Common causes: Common causes include Failed Engine Cooling Thermostat Heater, Engine Cooling Thermostat Heater harness is open or shorted, Engine Cooling Thermostat Heater circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 3,004

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on May 27, 2024

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
Comments
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Code P0597 Cadillac Description

The Engine Control Module (ECM) controls the Pulse Width Modulated (PWM) thermostat. The engine coolant thermostat heater controls coolant flow and regulates the engine operating temperature. The ECM supplies 12 V to the thermostat. The ECM controls the engine coolant thermostat heater by grounding the control circuit with a solid-state device called a driver. The driver is equipped with a feedback circuit that is pulled-up to a voltage. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage. The Diagnostic Trouble Code (DTC) will be set when the ECM detects that the commanded state of the driver and the actual state of the control circuit do not match for greater than 15 s.

OBDII Code P0597 Cadillac - Thermostat Heater Control Circuit Open - AutoCodes.com — P0597 Cadillac Code - Thermostat Heater Control Circuit Open

What does this mean?

What are the Possible Causes of the DTC P0597 Cadillac?

Failed Engine Cooling Thermostat Heater
Engine Cooling Thermostat Heater harness is open or shorted
Engine Cooling Thermostat Heater circuit poor electrical connection

How to Fix the DTC P0597 Cadillac?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

The engine coolant thermostat heater has a mechanical fail-safe in case of an electrical condition with the engine coolant thermostat heater. The mechanical thermostat will open at approximately 104Â°C (220Â°F). The mechanical thermostat will cycle from approximately 104Â°C (220Â°F) to approximately 98Â°C (208Â°F). The heater is part of the thermostat. The engine coolant thermostat heater and the thermostat housing are serviced as an assembly.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0597 Cadillac code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.