SCR NOx Pre-Catalyst Over Temperature Bank 2
The P20F1 code indicates that the Selective Catalytic Reduction (SCR) system's pre-catalyst NOx sensor on Bank 2 has detected an excessively high exhaust temperature. This can be caused by over-fueling, a malfunctioning diesel particulate filter (DPF) regeneration process, or a faulty temperature sensor. Prolonged overheating can damage the SCR catalyst and other exhaust components.
1. Most Common Causes
- Faulty NOx sensor or temperature sensor
- Excessive DPF regeneration frequency or duration
- Engine over-fueling or injector issues
- Exhaust gas recirculation (EGR) system malfunction
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance or limp mode
- Increased exhaust smoke
- Poor fuel economy
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and check freeze frame data.
Step 2: Inspect the NOx sensor and temperature sensor wiring and connectors for damage.
Step 3: Monitor live data for NOx sensor and exhaust temperature readings.
Step 4: Check DPF regeneration history and perform a forced regeneration if needed.
Step 5: Test fuel injectors and EGR system for proper operation.
4. 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 and other components. Limp mode may limit speed.
How much does it cost to fix?▼
Costs vary from $150 for a sensor replacement to $600 or more if the SCR catalyst or DPF needs replacement.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.