SCR NOx Pre-Catalyst Over Temperature Bank 2
The P20F1 code indicates that the Selective Catalytic Reduction (SCR) system's NOx pre-catalyst temperature sensor on Bank 2 has detected an excessively high temperature. This can be caused by excessive fuel in the exhaust (e.g., from incomplete combustion or post-injection), a malfunctioning diesel particulate filter (DPF) regeneration process, or a faulty temperature sensor. Overheating can damage the SCR catalyst and reduce NOx reduction efficiency.
01. Most Common Causes
- Faulty NOx pre-catalyst temperature sensor
- Excessive fuel in exhaust due to injector issues or post-injection problems
- Malfunctioning DPF regeneration causing high exhaust temperatures
- Wiring or connector issues in the sensor circuit
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance or power
- Increased fuel consumption
- Possible limp mode activation
03. Step-by-Step Diagnosis
Step 1: Scan for additional codes and freeze frame data.
Step 2: Inspect the NOx pre-catalyst temperature sensor and its wiring for damage or corrosion.
Step 3: Monitor sensor readings with a scan tool; compare to expected values during engine operation.
Step 4: Check for exhaust leaks or issues with DPF regeneration cycles.
Step 5: Test fuel injectors and post-injection system for proper operation.
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 high exhaust temperatures can damage the SCR catalyst and other components. Seek repair promptly.
How much does it cost to fix?▼
Costs vary from $150 to $600 depending on the cause. Sensor replacement is typically $150-$300, while injector or DPF-related repairs can be higher.