P0491

Secondary Air System Fault Bank 1.

P0491 - Secondary air system fault bank 1.: Last occurrence - minimum signal

Possible causes:
1. Low secondary air flow to bank 1.

1. Low secondary air flow to bank 1.
There is low secondary air flow to one of the cylinder banks.

Check the following:
- Electrical connections between the relay and the pump.
- Secondary air pump is functioning correctly.
- Secondary air valve is opening and sealing correctly.
- Secondary air pipes for leaks and blockages.