What Does P20F6 Mean?
The DEF injector on Bank 1 Unit 1 is mechanically stuck in the open position and cannot close properly. This causes continuous DEF injection even when not commanded.
Common Causes
45%
DEF crystallization causing injector valve to seize in open position
30%
Internal injector solenoid failure preventing valve closure
15%
Contaminated DEF causing deposits and valve sticking
8%
Failed injector return spring or damaged valve seat
2%
Shorted DEF injector driver circuit keeping injector energized
Diagnostic Steps
1
Step 1: Command DEF injector off and monitor system pressure; pressure should hold if injector closes properly
2
Step 2: Disconnect DEF injector electrical connector and retest pressure holding to rule out electrical short
3
Step 3: Remove DEF injector and inspect for crystallization, deposits, or mechanical damage
4
Step 4: Test injector solenoid resistance and compare to specifications (typically 3-8 ohms)
5
Step 5: Check DEF control module output for proper switching and absence of shorts to power
Estimated Repair Cost
$350 - $1,500
Parts + labor, varies by vehicle and location
The DEF injector on Bank 1 Unit 1 is mechanically stuck in the open position and cannot close properly. This causes continuous DEF injection even when not commanded.
The most common cause of P20F6 (Reductant Injection Valve Stuck Open Bank 1 Unit 1) is: DEF crystallization causing injector valve to seize in open position
Typical repair costs for P20F6 range from $350 to $1,500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle is safe to drive but will experience rapid DEF depletion and potential SCR catalyst damage. May trigger engine derate if condition persists.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P20F6 to identify the root cause.
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Quick Info
Category
Powertrain
System
Emissions Control System (SCR)
Difficulty
Type
Generic (SAE)
Recommended Tools
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