What Does P202A Mean?
The diesel exhaust fluid (DEF) tank heater control circuit is open or not functioning. This prevents proper heating of the DEF/reductant tank in cold conditions, which can lead to DEF freezing and SCR system issues.
Common Causes
35%
Broken or disconnected wiring to DEF tank heater
30%
Failed DEF tank heater element
20%
Blown fuse or failed relay in heater circuit
10%
Failed DEF heater control module or driver circuit
5%
Corroded or damaged heater connector
Diagnostic Steps
1
Step 1: Visually inspect DEF tank heater wiring harness and connectors for damage, corrosion, or disconnection
2
Step 2: Check fuses and relays associated with DEF heater circuit
3
Step 3: Measure resistance of DEF tank heater element, compare to specifications (typically 1-5 ohms)
4
Step 4: Test for power and ground at heater connector with key on, heater commanded on
5
Step 5: Check control module output signal to heater using multimeter or scope
Estimated Repair Cost
$200 - $800
Parts + labor, varies by vehicle and location
The diesel exhaust fluid (DEF) tank heater control circuit is open or not functioning. This prevents proper heating of the DEF/reductant tank in cold conditions, which can lead to DEF freezing and SCR system issues.
The most common cause of P202A (Reductant Tank Heater Control Circuit/Open) is: Broken or disconnected wiring to DEF tank heater
Typical repair costs for P202A range from $200 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive temporarily, but SCR system may not function in cold weather. Extended operation may trigger engine derate or prevent starting 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 P202A 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
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