What Does P20C1 Mean?
The PCM has detected an open circuit or complete loss of continuity in the control circuit for reductant heater C. This prevents heater operation and may affect DEF system functionality in cold weather.
Common Causes
35%
Broken or open circuit in wiring harness
30%
Failed reductant heater C with open element
20%
Disconnected or improperly seated connector
10%
Severely corroded connector pins creating open circuit
5%
Faulty control module unable to drive circuit
Diagnostic Steps
1
Step 1: Inspect all connectors in heater C circuit for proper connection and locking mechanism engagement
2
Step 2: Disconnect heater C and measure resistance across heater element terminals (compare to specifications)
3
Step 3: Test continuity of control circuit wiring from control module to heater connector
4
Step 4: Inspect wiring harness thoroughly for breaks, especially at flex points and mounting brackets
5
Step 5: Check power supply and ground circuits at heater connector with key on to verify circuit integrity
Estimated Repair Cost
$150 - $700
Parts + labor, varies by vehicle and location
The PCM has detected an open circuit or complete loss of continuity in the control circuit for reductant heater C. This prevents heater operation and may affect DEF system functionality in cold weather.
The most common cause of P20C1 (Reductant Heater "C" Control Circuit/Open) is: Broken or open circuit in wiring harness
Typical repair costs for P20C1 range from $150 to $700, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to operate in warm weather conditions. In freezing temperatures, lack of heater function may cause DEF crystallization, SCR system malfunction, and possible engine derate or performance restrictions.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P20C1 to identify the root cause.
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Quick Info
Category
Powertrain
System
Emissions - Selective Catalytic Reduction (SCR)
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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