Reductant Consumption Too High
The P20F5 code indicates that the engine control module (ECM) has detected that the diesel exhaust fluid (DEF) consumption is exceeding the expected rate. This is typically caused by issues in the selective catalytic reduction (SCR) system, such as a faulty DEF injector, incorrect DEF quality, or a malfunctioning NOx sensor. The system monitors DEF usage and compares it to engine operating conditions; when consumption is too high, the code is set to alert the driver and technician.
01. Most Common Causes
- Faulty DEF injector causing over-injection
- Incorrect DEF concentration or contamination
- Malfunctioning NOx sensor providing false readings
- Leaking DEF lines or connections
- ECM software issues or calibration errors
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance or power
- Increased DEF consumption
- Possible limp mode activation
- Excessive exhaust smoke or odor
03. Step-by-Step Diagnosis
Step 1: Scan the vehicle for all stored codes and freeze frame data.
Step 2: Inspect DEF level and quality; test with a refractometer.
Step 3: Check DEF injector operation and spray pattern.
Step 4: Monitor NOx sensor readings with a scan tool.
Step 5: Inspect DEF lines and connections for leaks.
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 performance and potential damage to the SCR system. The vehicle may enter limp mode, limiting speed and power.
How much does it cost to fix?▼
The cost to diagnose and repair P20F5 typically ranges from $50 to $150 for diagnosis, plus parts and labor. DEF injector replacement can cost $200-$500, while NOx sensor replacement may be $300-$600.