What Does P20CA Mean?
The reductant (DEF/urea) injection system has detected an air pressure leak in the delivery circuit. This affects the selective catalytic reduction (SCR) system's ability to properly inject emissions-reducing fluid into the exhaust stream.
Common Causes
35%
Damaged or cracked reductant supply lines or fittings
25%
Faulty reductant pressure sensor providing incorrect readings
20%
Leaking reductant pump seals or internal pump failure
15%
Failed reductant injector seals allowing air intrusion
5%
Loose or corroded electrical connections at pressure sensor
Diagnostic Steps
1
Step 1: Perform visual inspection of all DEF lines, connections, and fittings for visible damage, crystallization, or leaks
2
Step 2: Monitor live data for reductant pressure readings during system operation and compare to manufacturer specifications
3
Step 3: Perform smoke test or pressure decay test on reductant delivery system to isolate leak location
4
Step 4: Test reductant pressure sensor with multimeter and compare resistance/voltage to specifications
5
Step 5: Inspect DEF pump and injector for seal integrity and proper mounting
Estimated Repair Cost
$200 - $1,200
Parts + labor, varies by vehicle and location
The reductant (DEF/urea) injection system has detected an air pressure leak in the delivery circuit. This affects the selective catalytic reduction (SCR) system's ability to properly inject emissions-reducing fluid into the exhaust stream.
The most common cause of P20CA (Reductant Injection Air Pressure Leakage) is: Damaged or cracked reductant supply lines or fittings
Typical repair costs for P20CA range from $200 to $1,200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Not immediately dangerous to drive but will cause emissions system failure. May result in reduced engine power (derate) if not repaired within system-defined timeline.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P20CA to identify the root cause.
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Quick Info
Category
Powertrain
System
Emissions Control - Selective Catalytic Reduction
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
