P1423 Secondary Air Injection System, Bank 1: Flow Too Low

Not urgent

The measured value is lower than the ECU expects here. Treat this as a real physical shortfall first - check the part and what feeds it before suspecting the wiring.

Can you drive it? This is an emissions/EVAP fault. It will not hurt the engine and the car drives normally, but it will fail an emissions test and keeps the light on.

The definition

P1423: Secondary Air Injection System, Bank 1: Flow Too Low.

P1423 is a manufacturer-specific powertrain code (the engine or gearbox). Its meaning is set by the carmaker rather than by the SAE standard, so a generic OBD-II reader will often show it as an unknown code or misread it.

What to check first

Cheapest and fastest checks first:

Read the freeze-frame data stored with the fault - engine speed, load and temperature at the moment it logged tell you whether this happens cold, hot or under load.
Check the connector at the part for corrosion, and that it is fully seated.
Clear the code and see whether it returns, and under what conditions.

Reading the code is the easy part

A code names the circuit that complained. What tells you why is watching the sensor behind it while the engine runs — and that is where a code reader stops and a diagnostic tool starts.

VAGPULSE reads every module in a VW, Audi, Skoda or SEAT — not just the engine — shows the live measuring blocks behind this fault, gives you the freeze-frame conditions it was logged under, and clears it once you have fixed it. It also does what a generic OBD reader cannot on a VAG: service resets, coding, adaptations, and Stage 1–3 flashing with your original file saved first.

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Prefer to work on your phone? The VAGPULSE Android app is a free download and its demo mode runs against a sample car with no hardware at all, so you can see exactly what it reads before spending anything. Reading your car with it needs the VAGPULSE cable, which comes with the licence.

Common questions

What does P1423 mean?

P1423 means Secondary Air Injection System, Bank 1: Flow Too Low. The measured value is lower than the ECU expects here. Treat this as a real physical shortfall first - check the part and what feeds it before suspecting the wiring.

Can I drive with P1423?

This is an emissions/EVAP fault. It will not hurt the engine and the car drives normally, but it will fail an emissions test and keeps the light on.