What Does P20BD Mean?
The PCM has detected an open circuit or loss of continuity in the control circuit for reductant heater B. This prevents the heater from functioning, risking DEF freezing in cold conditions.
Common Causes
35%
Open circuit in wiring harness or broken wire
25%
Disconnected or loose electrical connector
25%
Failed reductant heater B element (open circuit)
10%
Corroded connector pins causing high resistance/open
5%
Faulty heater control module
Diagnostic Steps
1
Step 1: Visually inspect all connectors in heater B circuit for proper seating and secure connections
2
Step 2: Disconnect heater B connector and measure heater element resistance (should be within specifications)
3
Step 3: Check continuity of control circuit wiring from PCM/control module to heater connector
4
Step 4: Inspect wiring harness for physical damage, chafing, or breaks especially near mounting points
5
Step 5: Test voltage supply and ground circuits at heater connector with key on
Estimated Repair Cost
$150 - $700
Parts + labor, varies by vehicle and location
The PCM has detected an open circuit or loss of continuity in the control circuit for reductant heater B. This prevents the heater from functioning, risking DEF freezing in cold conditions.
The most common cause of P20BD (Reductant Heater "B" Control Circuit/Open) is: Open circuit in wiring harness or broken wire
Typical repair costs for P20BD range from $150 to $700, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive in warm weather. In freezing conditions, DEF may crystallize leading to SCR system failure, reduced engine power (derate), and potential no-start conditions.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P20BD 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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