Reductant Tank Heater Control Circuit/Open
The P202A code indicates a fault in the reductant (DEF) tank heater control circuit. The powertrain control module (PCM) has detected an open or malfunction in the electrical circuit that controls the heater element inside the DEF tank. This heater prevents DEF from freezing in cold temperatures. An open circuit means there is a break in the wiring, connector, or the heater element itself, preventing current flow.
01. Most Common Causes
- Open or shorted wiring in the reductant tank heater circuit
- Faulty reductant tank heater element
- Corroded or damaged connector at the heater
- Blown fuse or relay for the heater circuit
- Failed PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine performance or limp mode
- Increased diesel exhaust fluid (DEF) consumption
- Possible inability to start in cold weather if DEF freezes
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect the DEF tank heater connector and wiring for damage, corrosion, or loose connections.
Step 3: Using a multimeter, check for continuity and resistance in the heater circuit. Compare to manufacturer specifications.
Step 4: Check the fuse and relay for the reductant tank heater; replace if blown.
Step 5: If all else is good, test the heater element itself by measuring resistance at the tank; replace if open or out of spec.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally safe to drive short distances in warm weather, but in cold climates the DEF may freeze, causing the vehicle to enter limp mode or prevent starting. It's best to repair promptly.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on whether it's a simple wiring repair or replacement of the heater element.