Fault Code P0491
Code meaning, symptoms, possible causes, part number, and estimated cost.
P0491
Secondary Air Injection System Insufficient Flow (Bank 1)
This code indicates insufficient flow in the secondary air injection system on Bank 1. This system helps reduce emissions after a cold engine start.
Part Details
Part Name
Secondary Air Injection System
Reference P/N (OEM)
N/A
General part number for this fault code — not necessarily for your specific vehicle
Estimated Cost
₪500 - ₪1800
Engine Location
Exhaust system
Symptoms
- Check Engine Light on
- Failure of emissions test
- Unusual noise from air pump
- Slight decrease in engine performance
Possible Causes
- 1Faulty secondary air injection pump
- 2Stuck or faulty check valve
- 3Clogged or leaking vacuum/air hoses
- 4Damaged wiring or relay
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