Reductant Tank Heater Control Circuit High
The P202C code indicates that the powertrain control module (PCM) has detected a high voltage condition in the reductant (DEF) tank heater control circuit. This heater is used to prevent the diesel exhaust fluid from freezing in cold temperatures. A high voltage reading typically points to a short to power, a faulty heater element, or a problem with the control circuit wiring or connector.
01. Most Common Causes
- Short to voltage in the heater control circuit
- Faulty reductant tank heater element
- Damaged wiring or connector in the heater circuit
- Failed PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance or limp mode
- Possible DEF system warning messages
- Inability to start engine in cold weather (if DEF frozen)
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 tank heater wiring and connector for damage, corrosion, or loose connections.
Step 3: Measure resistance of the heater element; compare to manufacturer specifications (typically 1-5 ohms).
Step 4: Check for voltage at the heater connector with the ignition on; should be battery voltage. If voltage is higher than expected, trace short to power.
Step 5: If all checks pass, suspect a faulty PCM and perform further diagnostics per service manual.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally not recommended to drive with this code, as it can lead to reduced engine performance, limp mode, or failure to start in cold weather. Additionally, the DEF system may not function properly, potentially causing emissions issues.
How much does it cost to fix?▼
The cost to fix P202C typically ranges from $50 to $150 for diagnosis and repair, depending on the cause. If the heater element needs replacement, parts can cost $30-$80, and labor $50-$100. Wiring repairs are usually less expensive.