P2B59: Engine Coolant Flow Control Valve Control Circuit/Open

P2B59 is the open-circuit check for the drive of the coolant flow control valve. In GM's 25OBDG04B (3.0 L Duramax) the driver reports a load resistance above 200 kΩ, meaning one of the motor wires is disconnected; 80 of 100 samples set a Type B fault. Hyundai and Kia also use the code on the 2.5-litre Theta III engines with an integrated thermal management module (ITM): bulletins 26-EM-009H (Sonata, Tucson) and Kia TSB ENG 264 (K5, Sorento, Sportage, 2024–2025) describe P2B59F0 caused by an ECU logic error and fix it with new software, noting no driveability effect. Otherwise check the connector, the harness and the valve motor. Shorts to ground and to supply are reported separately as P2B5A and P2B5B.

Symptoms

• MIL on, often without any noticeable driveability change
• Valve stays in its default position, slower warm-up possible

Most likely causes

• ECU judgement logic on Hyundai/Kia 2.5 Theta III (software update 26-EM-009H / ENG 264)
• Valve connector unplugged, loose or with a pushed-out terminal
• Motor wire broken in the harness or valve motor winding open

What to check, in order

Start with the simplest. You can tick off each step.

1. With the engine cold, check the coolant level; never do this when the system is hot
2. Check the continuity of the wire between the component and the control module.
3. Check the actual temperature in live data
4. Make sure the fan comes on when it should
5. Check the thermostat and connector
6. Measure the sensor and replace it if its readings do not make sense

Good to know

• Repair difficulty: medium
• It affects emissions.

What each character of P2B59 means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• B: Subsystem depends on the code range
• 59: Specific fault in that system

Frequently asked questions

Can I keep driving with code P2B59?

Watch the temperature gauge. If it climbs or a warning appears, stop the car in a safe place and turn off the engine: overheating can cause serious damage.

What causes code P2B59?

The most common causes are: eCU judgement logic on Hyundai/Kia 2.5 Theta III (software update 26-EM-009H / ENG 264); valve connector unplugged, loose or with a pushed-out terminal; motor wire broken in the harness or valve motor winding open.

Related codes

• P2B5AEngine Coolant Flow Control Valve Control Circuit Low
• P2B5BEngine Coolant Flow Control Valve Control Circuit High
• P2B58Engine Coolant Flow Control Valve Motor Current High
• P2B5CEngine Coolant Flow Control Valve Supply Circuit Low

Sources

• gsi.ext.gm.com: 25OBDG04B
• static.nhtsa.gov: MC 11030329 0001
• static.nhtsa.gov: MC 11030379 0001
• static.nhtsa.gov: MC 10224856 0001

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.