Reductant Heater Control Circuit Performance
The P20C2 code indicates that the powertrain control module (PCM) has detected a performance issue in the control circuit of the diesel exhaust fluid (DEF) heater. This heater is responsible for preventing DEF from freezing in cold temperatures, ensuring proper operation of the selective catalytic reduction (SCR) system. The code is set when the heater's current draw or voltage is outside the expected range, often due to a faulty heater element, wiring issues, or a defective relay.
01. 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
02. Symptoms You Will Notice
- Illuminated check engine light
- Reduced engine performance or limp mode
- Increased diesel exhaust fluid consumption
- Possible failure of SCR system to reduce NOx emissions
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve all stored codes and freeze frame data.
Step 2: Visually inspect the DEF heater wiring and connectors for damage, corrosion, or loose connections.
Step 3: Test the heater circuit for proper voltage and ground using a multimeter.
Step 4: Measure the resistance of the DEF heater element and compare to manufacturer specifications.
Step 5: Check the fuse and relay for the DEF heater circuit.
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 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 P20C2 typically ranges from $50 to $150 for parts and labor, depending on the root cause. Replacing the DEF heater element may cost more if the part is expensive.