Reductant Purge Control Valve Stuck Closed
The P20A5 code indicates that the reductant purge control valve, part of the diesel exhaust fluid (DEF) system, is stuck in the closed position. This valve is responsible for purging excess DEF from the system to prevent crystallization and blockages. When stuck closed, DEF cannot be purged, leading to potential system pressure buildup, injector clogging, and reduced NOx conversion efficiency. This can trigger the check engine light and may eventually cause the vehicle to enter limp mode to protect the emissions system.
01. Most Common Causes
- Faulty reductant purge control valve
- Electrical issues (open/short circuit in valve wiring)
- DEF contamination or crystallization blocking the valve
- Faulty DEF control module
02. Symptoms You Will Notice
- Check engine light illuminated
- Reduced engine performance or limp mode
- Increased diesel exhaust fluid consumption
- Possible DEF system warning messages on dashboard
03. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm code P20A5 and check for related codes.
Step 2: Visually inspect the reductant purge control valve and its wiring for damage or corrosion.
Step 3: Test the valve's electrical resistance with a multimeter; compare to manufacturer specs.
Step 4: Check for DEF crystallization around the valve and clean if necessary.
Step 5: If valve is faulty, replace it and clear the code; test drive to verify repair.
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 DEF system. The vehicle may enter limp mode, limiting speed and drivability.
How much does it cost to fix?▼
The cost to fix P20A5 typically ranges from $50 to $150 for parts and labor, depending on the valve price and shop rates. DIY replacement can be cheaper if you have the tools.