OBD error - fuel system status - closed loop, using O2 sensor for fuel mix

[NeilTee]

I have 2001 1.4L 6N2, with 107k miles.

The check engine light intermittently appears, and after a few weeks it extinguishes, and then will re-appear...

I have connected an OBD module and it is telling me the following:
"fuel system status - closed loop, using O2 sensor for fuel mix"

if I rev it slightly, with the OBD module connected, as the revs die I also get the follow appear, before returning to the above message at idle:
"fuel system status - open loop due to engine load or deceleration"

Both are linked to an error code of P0441

The car runs fine, engine temp is stable. I've now cleared the error & check engine light (again), and drove to work this morning, and it's not re-appeared, but it will...

Does anyone know what is causing this?

Thanks.

[alexperkins]

VAG Error Code: 16825
EOBD II Error Code: P0441

Fault Location:
Evaporative Emission (EVAP) System - Incorrect Flow Detected

Possible Cause:
Malfunction Indicator Lamp (MIL)(K83) active.

Missing or loose fuel cap.
Incorrect fuel filler cap used.
Fuel filler cap remains open or fails to close.
Foreign matter caught in fuel filler cap.
Incorrect fuel tank vacuum relief valve.
Evaporative Emission (EVAP) Purge Solenoid (N80) faulty/jammed.
Evaporative Emission (EVAP) Canister Purge Solenoid Valve (N115) faulty/jammed.
Evaporative Emission (EVAP) Canister Sealing faulty.
Pipes between Tank Breathing and Throttle Body leaky/blocked.
Hose connection(s).
Intake leak.

Possible Solutions:
Check Evaporative Emission (EVAP) Purge Solenoid (N80).
Perform Output Test.
Check Evaporative Emission (EVAP) Canister Purge Solenoid Valve (N115).
Check Evaporative Emission (EVAP) Canister.
Perform Basic Setting.
Check Pipes between Tank Breathing and Throttle Body.

Special Notes:
When found in the North American Region (NAR) 1.8T Audi A4 1.8T check Technical Service Bulletin (TSB) 24-08-78 or 2010268/3 or Pass-Thru equivalent Technical Service Bulletin (TSB).
When found in the North American Region (NAR) 1.8T VW Passat 1.8T check Technical Service Bulletin (TSB) 01-09-09 or 2005554 or Pass-Thru equivalent Technical Service Bulletin (TSB).
Note: The Passat 26E5 or "R5" recall includes the same software update.
Make sure the quick release lines for the Check Evaporative Emission (EVAP) Purge Solenoid (N80) and vacuum line to LDP are not crossed.
This can also make the engine hard to start after filling up the fuel tank.

Tech Notes:
The P0441 code means that the control module has detected a leak in the Evaporative Emission (EVAP). Loose fuel tank filler cap is the most common cause that triggers the P0441 code.

When is the code detected?:
Pressure in charcoal canister and fuel tank does not drop during purge control (2 trip detection logic).

Description:
The Engine Control Module (ECM) tests the Evaporative Emission (EVAP) system for the following conditions:

- Large and small leaks.
- Excess vacuum.
- Purge flow during non-commanded conditions.
- Fuel Level and Fuel Pressure sensor faults.
- EVAP Purge and Vent Valve faults.

The Engine Control Module (ECM) monitors the Fuel Tank Pressure sensor in order to determine the level of vacuum/pressure in the EVAP system. The ECM commands both the EVAP Purge Solenoid and the EVAP Vent Valve ON when the conditions are met in order to apply an engine vacuum to the EVAP system. The Engine Control Module (ECM) commands the EVAP Purge Solenoid OFF once the system has reached a predetermined level of vacuum. This test verifies if a vacuum can be achieved in the EVAP system. Failure to develop a vacuum may be caused by a large leak or a restriction.

[NeilTee]

many thanks Alex.

What actually is EVAP?

[alexperkins]

It's the charcoal canister that helps control emissions

[NeilTee]

Thanks Alex.

so a couple more Q's, if I may, as you clearly know your stuff...

1. where do I find the charcoal canister?
2. I've read several items suggesting it can be removed?

TIA.

[alexperkins]

Its on the left hand side of the engine bay under the air intake near the wing

I wouldnt set about removing it - youll get a fuelly smell at the front of the car, plus it might drop your economy.

[NeilTee]

Again, thanks Alex.