Reductant Consumption Too High
The P20F5 code indicates that the diesel exhaust fluid (DEF) or reductant consumption is higher than expected by the engine control module (ECM). This typically points to a leak in the DEF system, a faulty DEF injector, or an issue with the selective catalytic reduction (SCR) system causing excessive dosing. The ECM monitors DEF usage via level sensors and compares it to expected consumption based on driving conditions; when actual usage exceeds the threshold, this code sets.
1. Most Common Causes
- DEF system leak (hoses, tank, injector)
- Faulty DEF injector (stuck open or leaking)
- DEF quality issues (contaminated or incorrect fluid)
- SCR system malfunction (e.g., failed NOx sensor causing over-dosing)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance or limp mode
- Increased DEF consumption (noticeable refills)
- Possible white smoke from exhaust
3. Step-by-Step Diagnosis
Step 1: Visually inspect the entire DEF system for leaks, including hoses, tank, and injector.
Step 2: Use a scan tool to monitor DEF level and consumption data; compare to expected values.
Step 3: Check DEF quality (use a refractometer or test strip) and replace if contaminated.
Step 4: Test the DEF injector for proper operation (leak test or actuation test).
Step 5: Inspect NOx sensors and SCR catalyst for damage or malfunction.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally not recommended to drive long distances, as high DEF consumption can lead to reduced engine performance, limp mode, and potential damage to the SCR system. Short trips may be okay, but the underlying issue should be addressed promptly.
How much does it cost to fix?▼
The cost varies depending on the cause. A simple leak repair may cost $50-$150, while replacing a DEF injector or NOx sensor can range from $200-$600. Diagnosis fees are typically $100-$200.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.