What Does P20EB Mean?
The power relay supplying the DEF control module is remaining energized longer than specified during shutdown. This timing issue can affect proper system purge and may drain the battery.
Common Causes
40%
Stuck DEF power relay contacts
30%
Failed DEF control module not releasing relay properly
15%
Shorted relay control circuit or wiring
10%
Faulty engine control module not sending proper shutdown signal
5%
Corroded or welded relay terminals
Diagnostic Steps
1
Step 1: Monitor relay control signal during shutdown with scan tool or oscilloscope
2
Step 2: Test relay for stuck contacts by measuring voltage at output terminal after shutdown
3
Step 3: Check DEF control module ground circuits for proper connection
4
Step 4: Inspect relay control wire for shorts to power or ground
5
Step 5: Test communication between engine control module and DEF control module during shutdown
Estimated Repair Cost
$150 - $900
Parts + labor, varies by vehicle and location
The power relay supplying the DEF control module is remaining energized longer than specified during shutdown. This timing issue can affect proper system purge and may drain the battery.
The most common cause of P20EB (Reductant Control Module Power Relay De-Energized Performance - Too Late) is: Stuck DEF power relay contacts
Typical repair costs for P20EB range from $150 to $900, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Minor safety concern. Extended relay energization may drain battery over time. May also affect proper DEF system purge procedures.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P20EB to identify the root cause.
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Quick Info
Category
Powertrain
System
Diesel Emissions Aftertreatment (SCR)
Difficulty
Type
Generic (SAE)
Recommended Tools
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