Reductant Heater Control Circuit High
The P20C0 code indicates that the powertrain control module (PCM) has detected a high voltage condition in the reductant heater control circuit. This circuit is responsible for heating the diesel exhaust fluid (DEF) in the tank to prevent freezing in cold temperatures. A high voltage reading typically points to a short to power, a faulty heater element, or a wiring issue. This code is common in diesel vehicles equipped with selective catalytic reduction (SCR) systems.
01. Most Common Causes
- Short to power in the reductant heater circuit
- Faulty reductant heater element
- Damaged wiring or connector
- Failed PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance or limp mode
- DEF system warning messages
- Increased emissions
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect the DEF heater wiring and connector for damage or corrosion.
Step 3: Measure voltage at the heater connector with the ignition on; compare to specifications.
Step 4: Test the heater resistance using a multimeter; replace if out of range.
Step 5: Check for shorts to power or ground in the control 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, as the DEF may freeze in cold weather, leading to reduced engine performance and potential damage to the SCR system.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for diagnosis and repair, but can be higher if the heater assembly or PCM needs replacement.