What does it mean?
P1423 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Secondary Air Pump Valve Plausibility . This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms
- MIL on and the secondary air monitor never sets to ready
- Pump runs on cold start but the expected exhaust reaction is missing or delayed
- Rough or uneven idle in the first minute of running
- Increased hydrocarbon emissions and possible test failure
- Occasional loud pump noise or a rattling valve
Likely causes
- Air valve stuck partly open or closed by carbon and moisture deposits
- Check valve leaking exhaust gas back into the air line, corroding the valve seat
- Weak or failing air pump that does not build the expected pressure
- Blocked or restricted air injection passages so pressure does not fall as expected
- Vacuum leak or split hose in the valve control line, leaving the valve partly actuated
- Pressure or flow sensor in the secondary air line reading incorrectly
- Damaged or disconnected air hose between the pump, valve and exhaust
How to fix it
- Watch live data on a cold start, comparing commanded valve state with the measured air pressure or flow value
- Inspect all air hoses for splits, softening and disconnection, and check the clamps
- Remove the air valve and check that it moves freely, cleaning carbon from the seat and plunger
- Test the check valve for reverse leakage by blowing through it in both directions
- Verify the pump builds pressure by measuring it in the delivery line while the pump is commanded on
- Test the valve control, whether vacuum or electric, and repair any leaking control hose
- Replace the failed valve, check valve or pump, then confirm plausibility with a fresh cold start monitor run