SCR NOx Catalyst Over Temperature Bank 1
The P20EC code indicates that the Selective Catalytic Reduction (SCR) catalyst on Bank 1 has exceeded its maximum operating temperature. This can lead to catalyst degradation and reduced NOx conversion efficiency. The SCR system uses diesel exhaust fluid (DEF) to reduce nitrogen oxides; overheating may be caused by excessive exhaust temperatures, DEF injection issues, or a malfunctioning temperature sensor.
01. Most Common Causes
- Faulty exhaust gas temperature sensor
- DEF injector malfunction or clogging
- Excessive engine load or regeneration cycles
- Exhaust system leaks or restrictions
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine power or limp mode
- Increased DEF consumption
- Poor fuel economy
03. Step-by-Step Diagnosis
Step 1: Scan for additional codes and freeze frame data.
Step 2: Inspect exhaust gas temperature sensor wiring and connector for damage.
Step 3: Check DEF injector for proper operation and spray pattern.
Step 4: Monitor live data for exhaust temperatures and DEF injection rates.
Step 5: Inspect exhaust system for leaks or blockages.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as overheating can damage the SCR catalyst, leading to costly repairs. Limp mode may activate, reducing power.
How much does it cost to fix?▼
Diagnosis typically costs $50-$150. Repair costs vary: sensor replacement $100-$300, DEF injector $200-$600, catalyst replacement $1,000-$3,000.