Reductant Heater Control Circuit Performance
The P20C6 code indicates that the powertrain control module (PCM) has detected a performance issue in the control circuit of the reductant heater, which is part of the selective catalytic reduction (SCR) system. This heater warms the diesel exhaust fluid (DEF) to prevent freezing and ensure proper injection. The code sets when the heater's actual performance deviates from expected parameters, often due to electrical faults or heater element failure.
1. Most Common Causes
- Deteriorated DEF heater element 'D' with resistance out of specification
- Harness, connectors, or terminals with corrosion, moisture, or high resistance in the control or power circuit
- Short to ground or voltage in the heater circuit wiring
- Faulty or open relay or fuse dedicated to the DEF heater
- Internal failure of the heater control driver in the powertrain control module (PCM)
2. Symptoms You Will Notice
- Illuminated check engine light
- Reduced engine performance or limp mode
- Increased diesel exhaust fluid consumption
- Failed emissions test
3. Step-by-Step Diagnosis
Step 1: Use a scan tool to confirm the code and check for related codes.
Step 2: Visually inspect the reductant heater wiring and connector for damage or corrosion.
Step 3: Test the heater circuit voltage and ground at the connector using a multimeter.
Step 4: Measure the resistance of the heater element; compare to manufacturer specs.
Step 5: Check the heater relay and fuse; replace if faulty.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally safe for short distances, but continued driving may lead to reduced performance, increased emissions, and potential damage to the SCR system. It's best to address the issue promptly.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on the cause. A simple relay or fuse replacement is cheaper, while a heater element replacement may be higher.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.