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 heater is part of the selective catalytic reduction (SCR) system, which uses diesel exhaust fluid (DEF) to reduce NOx emissions. A high voltage reading suggests a short to power, a faulty heater element, or a wiring issue. This can prevent the DEF from being properly heated, leading to reduced system efficiency and potential emissions non-compliance.
1. Most Common Causes
- Short to power in the reductant heater circuit
- Faulty reductant heater element
- Damaged wiring or connectors
- Corroded or loose electrical connections
- Failed PCM (rare)
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance
- Increased exhaust emissions
- Possible DEF system warning messages
- Failed emissions test
3. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for related codes.
Step 2: Visually inspect the reductant heater wiring and connectors for damage, corrosion, or loose connections.
Step 3: Measure the resistance of the heater element with a multimeter; compare to manufacturer specifications.
Step 4: Check for voltage at the heater connector with the ignition on; if voltage is present when it shouldn't be, trace the short to power.
Step 5: If all else is normal, test the PCM output or replace the PCM as a last resort.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally safe to drive short distances, but the vehicle may enter limp mode or fail emissions tests. Prolonged driving can damage 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 element or PCM needs replacement.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.