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Home / DTC / P20CA — Reductant Injection Air Pressure Leakage

P20CA — Reductant Injection Air Pressure Leakage

Detailed page for trouble code P20CA.

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P20CA

Generic P — Powertrain

Reductant Injection Air Pressure Leakage

Brand: Generic
Type: P — Powertrain
Views: UK: 19 EN: 19 RU: 24
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Page language: EN

Causes

  • Air supply line or fittings leaking (crack, loose, or disconnected)
  • Faulty air pressure sensor or incorrect sensor reading
  • Failed air supply solenoid/valve or stuck actuator
  • Damaged or clogged air filter / inlet restriction
  • Failed air pump/compressor or insufficient output
  • Cracked or degraded reductant dosing module seals or housing

Symptoms

  • MIL (check engine light) illuminated with P20CA stored
  • Reduced or inhibited reductant dosing leading to aftertreatment performance faults
  • Possible increased NOx emissions or regeneration faults
  • Hissing air noise from underhood or near reductant module
  • Warning messages related to SCR or DEF system
  • Hard starting or limp-home mode in severe cases (depending on vehicle strategy)

What to check

  • Retrieve freeze frame and freeze/clear code then attempt to re-create condition
  • Visually inspect all air lines, fittings, clamps and reductant injector sealing surfaces for damage or disconnection
  • Listen for air leaks during system activation (use care near moving parts and hot components)
  • Check air pressure sensor voltage or pressure reading with a scan tool while commanding system
  • Inspect operation of air supply pump and solenoids; verify power, ground and control signals
  • Check for contamination or crystallized reductant in lines and at injector

Signal parameters

  • Air supply line pressure (kPa or bar) — compare to specified target when commanded
  • Pressure sensor voltage or frequency signal at rest and during commanded pressurization (V)
  • Command duty cycle or ON/OFF status of air solenoid(s) (%)
  • Current draw of air pump/compressor (A) while operating
  • Time to reach target pressure or pressure decay rate when isolated (s / kPa/min)
  • Injector actuator feedback (position or response if applicable)

Diagnostic algorithm

  1. Connect a diagnostic scan tool, record freeze frame and live data for air pressure and related parameters. Clear the code and attempt to re-create while watching live data.
  2. Visually inspect air supply hoses, fittings, clamps and reductant injector for cracking, loose connections or external damage. Repair or replace as needed.
  3. With the system inactive, pressurize the air supply circuit (hand pump or shop pressure source limited to manufacturer-safe pressure) and check for leaks using soapy water or an electronic leak detector. Isolate and repair detected leaks.
  4. Command the air pump and solenoids with the scan tool. Verify pump runs, solenoid actuates and pressure rises to specification. If pump won’t run, check fuses, relays, power and ground.
  5. Measure pressure sensor output with a multimeter or compare to scan tool values. Replace sensor if out of range or inconsistent with applied pressure.
  6. Inspect and, if necessary, remove and clean or replace the air filter, check valve, and any moisture/contaminant traps. Clear any crystallized reductant from lines and injector interfaces.
  7. If no external leaks and components operate within specs, perform a bench test on solenoids and pump. Replace any components that fail electrical or functional tests.
  8. After repairs, clear DTCs, perform required regeneration or system learn procedures and verify the system holds pressure and the code does not return during road test or cyclic activation.
  9. If intermittent or unexplained, perform a smoke test of the complete air circuit and inspect wiring harnesses and connectors for corrosion or intermittent faults. Consider software/ECU updates if manufacturer bulletins apply.

Likely causes

  • Loose or split hose between compressor/air source and reductant injector
  • Faulty or leaking air pressure sensor (incorrect voltage/pressure reading)
  • Sticking/leaking purge or isolation solenoid in the reductant air circuit
  • Air pump not developing rated pressure due to wear or electrical fault
  • Damaged O-ring/seal at reductant injector or dosing module causing blow-by

Fault status

⚠️ Status
Reductant injection air pressure leakage detected — air supply to the reductant dosing system is leaking or not reaching required pressure. Diagnose air lines, pump/solenoid, pressure sensor and seals.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5-3.0 hours

Similar codes

P0442 P0440 P0299 P20C0 P20C1
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