P0491 - Secondary Air Injection Insufficient Flow Bank 1?

Hi all,

Background:
I have Citroen C3 (model year 2005) with the petrol engine (73hp).

Problem:
I am receiving the P0491 "insufficient air flow" fault code. However, it does not come always. Sometimes it comes after 1 week of driving, sometimes after 2 weeks. I.e. inconsequent behaviour even though my driving pattern is more or less the same every day.

Good to know:
I have Lexia and I have deactivated the secondary air pump in BSI through the configuration possible.
The pump is also detached from engine physically.

Questions:
Why is this specific diagnostic monitor still running( and thus popping P0491 DTC) if the car now is configured with not having the secondary air pump? No other diagnostic related to the secondary air injection pump is running (otherwise I would have received other electrical fault codes related to the pump as well if the car still believed the pump was there).

Is there something else I need to deactivate with Lexia? What is it?

/Tomson

Tomson wrote: ↑Thu Mar 23, 2023 6:42 pm
Good to know:
I have Lexia and I have deactivated the secondary air pump in BSI through the configuration possible.
The pump is also detached from engine physically.

Each ECU can "throw up" a fault code. You have mentioned "removing" the air injection system in the BSI but what about the engine ECU?
I am not familiar with the secondary air injection system on the C3. I know what it's for and how it works, I just don't know the specifics of the C3!
I would have assumed that the engine ECU would have had a say in the air injection system.
Nothing about air injection in the engine ECU?

Disconnecting any of the engine related electrical components will bring up a fault code. That is how the engine has been designed.

The engine Ecu is expecting to see the effects of a particular actuator relative to its performance Map. If the signal is sent to operate the actuator and no result is detected, a fault can be set.