What Does P20A0 Mean?
The powertrain control module has detected an open circuit or complete loss of communication with the diesel exhaust fluid (DEF) reductant purge control valve. This valve is responsible for purging air and preventing DEF crystallization in the injection system.
Common Causes
35%
Broken or disconnected wiring harness to purge valve
30%
Failed reductant purge control valve
20%
Corroded or damaged electrical connector terminals
10%
Blown fuse or failed relay in purge valve circuit
5%
PCM internal fault or software issue
Diagnostic Steps
1
Step 1: Visually inspect the purge valve connector and wiring for damage, corrosion, or disconnection
2
Step 2: Check fuses and relays related to the DEF/SCR system
3
Step 3: Measure voltage at the purge valve connector with key on to verify power supply
4
Step 4: Test purge valve resistance with multimeter (compare to specifications)
5
Step 5: Check wiring continuity between PCM and purge valve connector for open circuits
Estimated Repair Cost
$150 - $800
Parts + labor, varies by vehicle and location
The powertrain control module has detected an open circuit or complete loss of communication with the diesel exhaust fluid (DEF) reductant purge control valve. This valve is responsible for purging air and preventing DEF crystallization in the injection system.
The most common cause of P20A0 (Reductant Purge Control Valve Circuit /Open) is: Broken or disconnected wiring harness to purge valve
Typical repair costs for P20A0 range from $150 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle remains safe to drive temporarily but may enter reduced power mode. Continued operation without repair will lead to emission system degradation and potential DEF system crystallization.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P20A0 to identify the root cause.
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Quick Info
Category
Powertrain
System
Emissions Control System (SCR/DEF)
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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