What Does P202C Mean?
The DEF tank heater control circuit voltage is higher than expected. This indicates an open circuit, high resistance, or lack of current flow in the reductant heating system.
Common Causes
35%
Open circuit in DEF heater wiring or connector
30%
Failed open DEF tank heater element
20%
Poor ground connection for heater circuit
10%
High resistance in power supply circuit to heater
5%
Failed control module unable to complete circuit
Diagnostic Steps
1
Step 1: Check DEF heater connector for proper connection, bent pins, or corrosion
2
Step 2: Measure resistance of DEF tank heater element (should show specified resistance, not infinite)
3
Step 3: Test ground circuit continuity from heater to chassis ground
4
Step 4: Check for voltage drop in power supply circuit during heater operation
5
Step 5: Monitor control module command signal and actual current draw with scan tool
Estimated Repair Cost
$150 - $850
Parts + labor, varies by vehicle and location
The DEF tank heater control circuit voltage is higher than expected. This indicates an open circuit, high resistance, or lack of current flow in the reductant heating system.
The most common cause of P202C (Reductant Tank Heater Control Circuit High) is: Open circuit in DEF heater wiring or connector
Typical repair costs for P202C range from $150 to $850, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive temporarily. DEF may freeze in cold conditions leading to SCR system malfunction and eventual engine power reduction per emissions regulations.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P202C to identify the root cause.
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Quick Info
Category
Powertrain
System
Selective Catalytic Reduction (SCR) Emissions System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
