What does it mean?
P1420 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Secondary Air Injector Valve Circuit Electrical Malfunction .
Symptoms
- MIL on with the secondary air readiness monitor incomplete
- Air injection valve does not open, so no air reaches the exhaust during cold start
- Elevated hydrocarbon emissions and possible test failure
- Slightly rough cold idle that improves after warm up
- No audible click from the valve when it is commanded with a scan tool
Likely causes
- Open or high resistance in the valve control wire or its supply feed
- Corroded, loose or backed out terminals in the valve connector
- Internally open or shorted valve solenoid winding
- Damaged harness where it passes hot exhaust components or a sharp bracket
- Poor ground connection for the air injection circuit
- Blown fuse feeding the valve or a failed relay upstream of it
- PCM driver stage fault, only after all circuit checks pass
How to fix it
- Command the valve on and off with a scan tool and listen for the solenoid clicking
- Inspect the valve connector for corrosion, spread terminals and heat damage
- Measure the solenoid resistance and compare against specification; open or very low readings both indicate a faulty valve
- With the key on, verify battery voltage on the supply side of the valve connector
- Perform a voltage drop test on the control wire between the valve and the PCM while it is commanded
- Check the fuse and any relay feeding the air injection circuit
- Repair the wiring fault or replace the valve, then rerun a cold start monitor to confirm the repair