Reductant Heater Control Circuit Performance
The P20C6 code indicates that the powertrain control module (PCM) has detected a performance issue in the reductant heater control circuit. This heater is part of the Selective Catalytic Reduction (SCR) system, which uses diesel exhaust fluid (DEF) to reduce NOx emissions. The heater prevents DEF from freezing in cold temperatures. A performance fault means the circuit is not operating within expected parameters, often due to high resistance, short, or open circuit.
01. Most Common Causes
- Faulty reductant heater element
- Open or shorted wiring in the heater circuit
- Corroded or damaged connector at the heater
- Failed reductant heater relay or fuse
- Defective PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine power or limp mode
- Increased diesel exhaust fluid consumption
- Poor fuel economy
- Possible DEF system warning message on dashboard
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve freeze frame data and confirm the code.
Step 2: Visually inspect the reductant heater connector and wiring for damage, corrosion, or loose connections.
Step 3: Measure resistance of the heater element with a multimeter; compare to manufacturer specs (typically 0.5-5 ohms).
Step 4: Check for voltage at the heater connector with the ignition on; should be battery voltage (12V).
Step 5: Test the heater relay and fuse; replace if blown or faulty.
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, increased emissions, and potential damage to the SCR system. In cold climates, the DEF may freeze, causing further issues.
How much does it cost to fix?▼
The cost to fix P20C6 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 more expensive.