The P20B1: Reductant Heater Coolant Control Valve Circuit/Open fault code indicates an issue where the circuit controlling the reductant heater coolant control valve is open. This valve regulates coolant flow to the DEF heater, which is crucial for maintaining the correct temperature of the diesel exhaust fluid (DEF). An open circuit can disrupt this process, leading to improper DEF function and emissions control issues. Common causes include an open circuit in the wiring, a faulty valve, or a malfunctioning control module.
P20B1 – Quick Overview
| Code | Information |
|---|---|
| Meaning | P20B1: Reductant Heater Coolant Control Valve Circuit/Open |
| Is it serious? | Yes, it can cause the DEF system to malfunction, leading to improper emissions control and increased emissions. |
| Possible causes | – Open circuit in the heater coolant control valve wiring – Faulty heater coolant control valve – Faulty control module |
| How to diagnose? | – Inspect the wiring for open circuits – Test the heater coolant control valve – Check the control module functionality |
P20B1 Meaning
The P20B1 code indicates that the circuit responsible for controlling the reductant heater coolant control valve is open. This valve plays a critical role in heating the diesel exhaust fluid (DEF) to prevent it from freezing in colder temperatures, ensuring proper emissions control. An open circuit can cause the valve to fail, preventing it from regulating the coolant, which affects the DEF heating system.
Step-by-step diagnostic guide
| Action | Description | Tools Needed |
|---|---|---|
| Check for Other Codes | Use an OBD-II scanner to check for additional fault codes related to the emissions system or reductant heater, which might provide more context. | OBD-II Scanner |
| Inspect the Wiring for Open Circuits | Visually inspect the wiring connected to the heater coolant control valve for any signs of breaks, damage, or disconnections causing an open circuit. | Flashlight, Multimeter |
| Test the Heater Coolant Control Valve | Use a diagnostic tool to test the functionality of the valve, ensuring it is operating correctly and within manufacturer specifications. Replace if necessary. | Multimeter, Diagnostic Tool |
| Check the Control Module Functionality | Inspect the control module responsible for sending signals to the valve and ensure it is functioning properly. Check for errors in the control module. | Diagnostic Tool |
| Clear the Code and Test Drive | After completing repairs, clear the code using an OBD-II scanner and take the vehicle for a test drive to confirm that the issue has been resolved. | OBD-II Scanner, Vehicle Owner’s Manual |
| Recheck for Codes | Re-scan the system after the test drive to ensure that the P20B1 code does not return. If the code reappears, further diagnostics may be needed. | OBD-II Scanner |
Free PDF: How to choose OBD2 scanner
I’ve made you a free PDF to choose the OBD2 scanner in 5 minutes.
✅ Which OBD2 scanner is best?
✅ Which type should you get (DIY, Pro, Hobby)
✅ What is the best scanner for the exact brand/feature (e.g best for BMW)
✅ How to get a Bi-Directional tool for as cheap as $40
✅ Discount coupons for scanners
PDF is 100% free and it is designed to help you pick a scanner in less than a few minutes! Not a boring 50-page guide.
Just tell me where to send it.
Hi, I am Juraj “Yuri” Lukacko. I got frustrated by unhelpful and scammy mechanics, so I decided to learn everything about car diagnostics myself. I test dozens of new car diagnostic tools every month along with learning new strategies to fix and customize cars. About Juraj Lukacko (Yuri)