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 the DEF from freezing in cold temperatures, ensuring proper selective catalytic reduction (SCR) system operation. The code is set when the heater's current draw or resistance is outside the expected range, often due to a faulty heater element, wiring issues, or a defective relay.
1. Most Common Causes
- Faulty internal reductant heater 'C' (resistance out of specification)
- High resistance, corrosion, or damage in the heater 'C' circuit wiring or connectors
- Faulty reductant control module (RCM) or PCM
- Contaminated, incorrect, or frozen DEF fluid preventing proper heat transfer
- Blown fuse or defective heater power relay
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, corrosion, or loose connections.
Step 3: Test the heater element resistance with a multimeter and compare to manufacturer specifications.
Step 4: Check the fuse and relay for the reductant heater circuit.
Step 5: If all else is okay, replace the reductant heater assembly.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code for extended periods, as it can lead to reduced engine performance, increased emissions, and potential damage to the SCR system. In cold climates, the DEF may freeze, causing the vehicle to enter limp mode.
How much does it cost to fix?▼
The cost to fix a P20C2 code typically ranges from $50 to $150 for parts and labor, depending on the cause. Replacing the heater element or relay is usually affordable, but if wiring repairs are needed, costs may be higher.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.