Reductant Heater Control Circuit Low
The P20C7 code indicates that the powertrain control module (PCM) has detected a low voltage condition 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. A low circuit condition typically means the voltage is below the expected threshold, often due to a short to ground, faulty heater element, or wiring issues.
01. Most Common Causes
- Faulty reductant heater element
- Short to ground in the heater control circuit
- Open or damaged wiring/connectors
- Failed PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance or limp mode
- Increased diesel exhaust fluid consumption
- Possible DEF system warning messages
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve all stored codes and freeze frame data.
Step 2: Visually inspect the reductant heater wiring and connectors for damage, corrosion, or loose connections.
Step 3: Measure resistance of the heater element; compare to manufacturer specifications (typically 0.5-2 ohms).
Step 4: Check for voltage at the heater connector with the ignition on; should be battery voltage. If low, trace circuit for shorts or opens.
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 system may not function properly, leading to reduced engine performance and potential damage to the SCR system. In some cases, the vehicle may enter limp mode.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for diagnosis and repair, depending on the cause. Replacing the heater element or repairing wiring may cost more if parts are needed.