Understanding the P1422 Fault Code on Subaru Vehicles
What exactly does the OBD2 code P1422 mean?
The P1422 fault code is a manufacturer-specific code for Subaru that indicates a malfunction in the secondary EGR valve circuit. This system, also called the “secondary exhaust gas recirculation system,” plays a crucial role in reducing polluting emissions, particularly during the engine’s cold start phases. Unlike conventional EGR systems, the secondary system operates mainly during the first few minutes of engine operation to accelerate catalyst heating and improve exhaust gas treatment efficiency.
Operation of the secondary EGR system in Subaru
The Subaru secondary EGR system consists of several key components:
- Secondary EGR valve (electric or pneumatic control)
- Pressure and temperature sensors
- Secondary air accumulation reservoir
- Connection pipes to the exhaust manifold
- Engine control unit (ECU) for system management
This system injects fresh air into the exhaust gas flow to promote afterburning that quickly raises the catalyst temperature, enabling more effective reduction of harmful emissions from startup.
Main Causes of P1422 Code Triggering
Electrical problems and component failures
The most frequent causes of the P1422 code on Subaru include:
- Faulty secondary EGR valve: mechanical wear, blockage, or severe clogging
- Electrical circuit problems: cut wires, oxidized connectors, or poor contacts
- Control relay failure: inability to properly power the valve
- Defective sensors: pressure sensor or temperature probe providing incorrect information to the ECU
Mechanical problems and clogging
Beyond electrical issues, several mechanical factors can trigger P1422:
- Severe pipe clogging: accumulation of carbon deposits obstructing air passage
- System leaks: cracks in pipes or poor sealing joints
- Secondary air pump failure (on certain models): bearing wear or electric motor failure
- Engine vacuum problems: leaks affecting the operation of pneumatic systems
Aggravating factors specific to Subaru models
Certain Subaru models have particular vulnerabilities:
- Subaru Impreza (2002-2007 models): recurring problems with oxidized connectors
- Subaru Forester (SG/SH generations): accelerated clogging in urban use
- Subaru Legacy/Outback (4th generation): early control relay failures
Step-by-Step Diagnostic Procedure
Preparation and necessary tools
Before starting diagnosis, gather the appropriate tools:
- Professional OBD2 scanner compatible with Subaru
- Digital multimeter for electrical measurements
- Vacuum pump (for pneumatic tests)
- Specific cleaner for EGR circuits
- Technical documentation for the concerned model
Electrical diagnosis of the secondary EGR valve circuit
Start by checking the electrical circuit integrity:
- Check the valve supply voltage (generally 12V)
- Verify the circuit ground with the multimeter
- Test the valve coil resistance (specific values according to model)
- Visually inspect the condition of connectors and wiring
Functional tests and mechanical checks
Once the electrical aspect is validated, proceed to mechanical tests:
- Valve operation test with scanner (active command)
- System leak check under vacuum
- Visual inspection of secondary air pipes and conduits
- Inspection of the accumulation reservoir for possible damage
Repair Solutions and Estimated Costs
System cleaning and decoking
For moderate clogging cases, thorough cleaning can solve the problem:
- Disassembly and cleaning of the secondary EGR valve with specific products
- Cleaning of air conduits with compressed air and suitable solvents
- Check and clean the air filter (if present in the circuit)
- Reassembly with replacement of sealing joints if necessary
Replacement of defective components
In case of proven failure, replacement is necessary:
- New secondary EGR valve (original part recommended)
- Control relay and wiring repair if damaged
- Defective piping replaced with certified parts
- Associated sensors if values are out of specifications
Repair cost estimation
The total cost varies according to the necessary intervention:
- Complete system cleaning: €150-300 (labor included)
- Secondary EGR valve replacement: €300-600 depending on model
- Electrical circuit repair: €100-250
- Complete system replacement: €500-900 for the most severe cases
Consequences and Prevention of P1422 Code
Risks if not repaired
Ignoring a P1422 code can lead to serious complications:
- Significant increase in polluting emissions
- Premature degradation of the catalyst (high replacement cost)
- Increased fuel consumption
- Risk of failure at technical inspection
- Possibility of engine entering limp mode
Preventive measures to avoid fault recurrence
To minimize P1422 recurrence risks:
- Use of quality fuel and occasional cleaning additives
- Regular maintenance of the air intake system
- Periodic checks of electrical connections
- Replace air filter according to recommended intervals
- Avoid exclusively very short urban trips
The Subaru P1422 code, although specific, generally responds well to structured diagnostic procedures. A methodical approach allowing precise identification of the root cause avoids unnecessary component replacements and ensures durable repair of your vehicle’s anti-pollution system.