Reductant Heater Coolant Control Valve Circuit/Open
The P20B1 code indicates an open or malfunction in the circuit of the reductant heater coolant control valve. This valve regulates coolant flow to the reductant heater, which warms the diesel exhaust fluid (DEF) to prevent freezing. An open circuit means the electrical path is broken, preventing the valve from operating. This can lead to DEF not being heated properly, causing issues with the selective catalytic reduction (SCR) system and increased emissions.
01. Most Common Causes
- Faulty reductant heater coolant control valve
- Open or shorted wiring in the valve circuit
- Corroded or loose electrical connectors
- Blown fuse or relay issue
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance or limp mode
- Increased diesel exhaust fluid consumption
- Possible failed emissions test
03. Step-by-Step Diagnosis
Step 1: Scan the vehicle for codes and note any related codes (e.g., P20B0, P20B2).
Step 2: Visually inspect the reductant heater coolant control valve and its wiring harness for damage, corrosion, or loose connections.
Step 3: Use a multimeter to test the valve's resistance and check for continuity in the circuit. Compare to manufacturer specifications.
Step 4: Check the fuse and relay for the valve circuit; replace if blown.
Step 5: If wiring and power are okay, replace the reductant heater coolant control valve.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances with this code, as it can lead to reduced engine performance, increased emissions, and potential damage to the SCR system. You may experience limp mode.
How much does it cost to fix?▼
The cost to fix P20B1 typically ranges from $150 to $400, including parts and labor. The valve itself costs $50-$150, and labor is about $100-$250 depending on the shop.