P2434 Secondary air system: signal drops out at times (bank 1)

By: Diagno editorial team · Updated: 2026-10-15

P2434 means: Secondary air system: signal drops out at times (bank 1). The secondary air system blows air into the exhaust on a cold start so the catalytic converter warms up faster. OK to drive, but have it checked soon. The repair usually costs about €50–250 in Estonia.

What it means

The secondary air system blows air into the exhaust on a cold start so the catalytic converter warms up faster. The computer found too little air or a fault in the pump or valve control. The signal drops out now and then. The most common cause is a loose connector or a chafed wire.

What you may notice

• Engine light on
• Unusual pump noise on a cold start
• Usually no change in driving

What could be wrong

1. 1Connector loose, damp or corroded
2. 2Wire broken or chafed
3. 3Faulty air pump or valve
4. 4Engine computer fault (rare)

Repair difficulty: Moderate

What you can check yourself

First look at the connector and wiring: anything loose, melted or green with corrosion? On a cold start, listen for the pump droning in the engine bay for a few seconds. You can check the simple things yourself, but the repair is best done in a workshop.

How we fix it

1. We read the fault data on the diagnostic tool and check whether the fault is constant
2. We measure the circuit's supply, ground and signal
3. We repair the wire or replace the connector
4. If the wiring is fine, we replace the air pump or valve

Standard SAE description: Secondary Air Injection System Air Flow/Pressure Sensor Circuit Intermittent/Erratic Bank 1