I have a code P0491 coming up on my 2004 Dodge Stratis, this is a secondary fuel injection system and don't know wear to start to correct this.

codes p 0410, 0411, 0412 all refer to the secondary air injection system--malfunction, incorrect flow detected and circuit malfunction ===causes are --wiring--sir valve---air solenoid--ECM--air pump, air hose/s--ECM
code p 0491 refers to secondary air injection bank 1 --malfunction or insufficient flow=== causes are the same with a mechanical fault added
so to analyze -- the most common cause is air hoses, followed by valve or solenoid of the air injection system followed by ECM which be as little as a bad pin connection in the wiring

Did you check the Vacuum lines to the Secondary air Valve Controls. They may be rotten. Can you do a Smoke test. Replace dry rotted lines with either 3/16 Fuel or Power Steering Hoses if you do not get ORM Vacuum lines/hoses. There are many Vedios on You Tube showing this specific problem solving on German cars. you can check out these,
Secondary Air Injection Systems on German Vehicles E39) 2001 BMW 525i Resolve P0491/P0492 for less than $2.00 in approx 15min. How to Fix and Diagnose BMW P0491 P0492 Secondary Air / Vacuum Leak E36 E46 E39 E53

I’m happy to assist further over the phone at https://www.6ya.com/expert/uttamjeet_2f3adc18600f8ede

bank 1 is the side of the number 1 cylinder ---you didnt specify vehicle but this is a generic code and the following link will help you in solving your problem
P0491 Secondary Air Injection System Insufficient Flow Bank 1

can be fuse. wiring. valve. house is same think the dealer misssda at the diagnostic

P0491 - Secondary Air Injection System Insufficient Flow Bank 1
Possible causes
- Intake leak
- Damaged AIR system components
- Faulty AIR Solenoid Valve
- Faulty AIR system relay

P0491 Secondary Air Injection System (Bank 1)
P0492 Secondary Air Injection System (Bank 2)
Good luck for you!
OBD2 code reader

it can be the turbo

P0491 Secondary Air Injection System (Bank 1)
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car key programmer

P0410 - SECONDARY AIR INJECTION (AIR) SYSTEM
P0491 - SECONDARY AIR INJECTION (AIR) SYSTEM INSUFFICIENT FLOW (BANK 1)

Secondary air injection (trademarked as Air Injection Reactor) is a process where fresh air is injected into the exhaust system to allow for a fuller combustion of exhaust gasses.

The possible causes are:
SAIR pump low or now air flow
SAIR bypass solenoid leaking/blocked or stuck open/closed
SAIR diverter valve leaking/blocked or stuck open/closed
SAIR air hose restriction
SAIR vacuum hose restriction or leaking

Check to make sure your air filter isn't dirty - and replace if needed. Otherwise I would suggest having your local trusted auto repair facility diagnose and repair the issue. A scan tool will be needed to properly diagnose the issue.

P0491 Secondary Air System (Bank 1)