Reductant Heater Control Circuit Low
The P20BF code indicates that the powertrain control module (PCM) has detected a low voltage condition in the control circuit of the diesel exhaust fluid (DEF) heater. This heater is responsible for preventing the DEF from freezing in cold temperatures, ensuring proper operation of the selective catalytic reduction (SCR) system. A low circuit condition can be caused by a faulty heater element, damaged wiring, or a defective relay or fuse.
1. Most Common Causes
- Faulty DEF heater element
- Open or shorted wiring in the heater control circuit
- Blown fuse or defective relay
- Corroded or loose electrical connectors
2. Symptoms You Will Notice
- Illuminated check engine light
- Reduced engine performance or limp mode
- Increased diesel exhaust fluid consumption
- Possible failure of emissions tests
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve the code and freeze frame data.
Step 2: Visually inspect the DEF heater wiring and connectors for damage or corrosion.
Step 3: Test the heater circuit voltage and resistance with a multimeter.
Step 4: Check the fuse and relay for the DEF heater system.
4. 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 engine performance and potential damage to the SCR system. In some cases, the vehicle may enter limp mode.
How much does it cost to fix?▼
The cost to fix a P20BF code typically ranges from $50 to $150 for parts and labor, depending on the specific cause and vehicle model.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.