Secondary Air Injection System Pump Stuck Off (Bank 1)

Possible causes

• CommonSeized air pump, usually from water ingestion
• CommonBlown fuse on the pump circuit
• CommonFailed pump relay
• CommonWiring or connector fault at the pump
• CommonFailed check valve, which is what let the water in
• PossibleCorroded earth at the pump

What you might notice

• No pump noise on a cold start
• Check engine light on
• Failed emissions test
• Rough running for the first minute from cold
• Usually no symptom the driver notices

What to check, in order

1. Check the fuse and swap the relay first. Both are cheap and both are common.
2. Check for battery voltage at the pump connector while the system is commanded on a cold start. Voltage present with no pump running confirms a seized pump.
3. Check the pump earth connection.
4. Replace the one-way check valve at the same time as the pump. This is the important part: if you fit a new pump and leave the failed check valve in place, exhaust moisture will reach the new pump and it will seize as well.
5. Inspect the hoses for water sitting in them, which confirms the check valve has been letting exhaust gas through.