Reductant Heater Control Circuit Low
The P20C3 code indicates that the powertrain control module (PCM) has detected a low voltage condition in the control circuit for the diesel exhaust fluid (DEF) heater. This heater is essential for preventing DEF from freezing in cold temperatures, ensuring proper selective catalytic reduction (SCR) system operation. A low circuit condition typically points to a short to ground, open circuit, or a faulty heater element.
1. Most Common Causes
- Faulty DEF heater element
- Short to ground in heater control circuit
- Open circuit in heater wiring or connector
- Failed PCM (rare)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine power or limp mode
- Poor fuel economy
- Increased diesel exhaust fluid consumption
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and freeze frame data.
Step 2: Visually inspect DEF heater wiring and connector for damage, corrosion, or loose connections.
Step 3: Using a multimeter, measure resistance of the DEF heater element; compare to manufacturer specs.
Step 4: Check for voltage at the heater connector with the ignition on; if no voltage, test the control circuit for shorts or opens.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
Driving short distances in warm weather may be okay, but prolonged driving or cold temperatures can cause the DEF to freeze, leading to reduced engine power and potential SCR system damage. It's best to repair promptly.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on whether the heater element or wiring needs replacement. Diagnostic fees may add $50-$100.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.