Wife's car 23,000 miles bought 2 years ago from main dealer failed MOT on Check Engine Light Showing. This is the saga

🇨🇬

Check Engine light shows 2 days prior to MOT date, duly fails 25Aug26.☹️

• Connect ODB reader & it shows one DTC. (P0441 “Incorrect Purge Flow”)

• Check fuel tank cap & seal (All OK)

• Clear DTC

• Code returns within 1 mile whilst driving.

• Code P0441 detected

• Recheck fuel cap seal & start research in manual, forums & online. First port of call seems N80 solenoid valve.

• Code cleared,

• Code returns within 1 mile of driving.

• Cleaned pipes on inlet manifold & checked electrical connectors to N80 solenoid & GV 344 Pressure sensor.

• Small crack found on insulation of Pin1 wire on GX 344 sensor (manifold pressure), so checked conductor continuity – OK, but reinsulated wire with liquid tape.

• Used hot air gun to soften hard plastic pipes, removed & checked N80 Evap system solenoid valve – OK on & off the car – both solenoid & pipes are completely clean – no sign of debris/dust/charcoal.

• Code cleared,

• Code returns within 1 mile of driving.

• Conclude GX 344 sensor faulty – not available separately so:

• Bought new genuine VW/AG N80/GX344 plus pipe assembly (all in one with quick connectors) & fitted. (£117)

• Code cleared

• Test drive of 15-20 miles All OK😀

• Check Engine light shows following morning 1 mile after restart.😡🤔

• Connect ODB reader & it shows one DTC. (P0441 again)

• Remove rear wheel & wheelarch liner, investigate activated charcoal canister & blow through all pipes.

• Remove canister & weigh – 1.700 Kg

• Check for weight of new one which is 1.330 Kg

• Conclude canister is contaminated, so order new VW/AG one. (£167) 01Sep2026

• LLL Parts take 5 days to dispatch an apparently "in-stock" item then DPD/Evri delays so part gets to me late Sep 11th (outside of my 10 working days free MOT retest)😠

• Fit new canister (after checking weight!) Sat 12th & arrange retest for today 14th Sept (I've dealt with this garage for MOT's for over 35 years so they squeezed me in)

• PASS MOT

The actual mechanical work is very straightforward, I could change sensors/pipes & canister in an hour now I know exactly what to do, but I have a nagging thought that only the canister needed replacing & my gx344 & N80 were fine - I know the N80 is certainly OK. It took hours of reading about these over complex modern petrol engines to find why & how to do the job, but the job was simple even at my advanced years (76☹️)

Anyway, wifey is now happy so I suppose it was £384 well spent - cheaper than a new cooker anyway😇

Not much wrong with messing with cars when you are 76, keeps the brain active with the many challenges you meet and hopefully beat!

Edit:- a big 👍 to getting it sorted though.

Edited 11 hours ago11 hr by rum4mo

6 hours ago, JRL said:

Wife's car 23,000 miles bought 2 years ago from main dealer failed MOT on Check Engine Light Showing. This is the saga

🇨🇬

Check Engine light shows 2 days prior to MOT date, duly fails 25Aug26.☹️

• Connect ODB reader & it shows one DTC. (P0441 “Incorrect Purge Flow”)

• Check fuel tank cap & seal (All OK)

• Clear DTC

• Code returns within 1 mile whilst driving.

• Code P0441 detected

• Recheck fuel cap seal & start research in manual, forums & online. First port of call seems N80 solenoid valve.

• Code cleared,

• Code returns within 1 mile of driving.

• Cleaned pipes on inlet manifold & checked electrical connectors to N80 solenoid & GV 344 Pressure sensor.

• Small crack found on insulation of Pin1 wire on GX 344 sensor (manifold pressure), so checked conductor continuity – OK, but reinsulated wire with liquid tape.

• Used hot air gun to soften hard plastic pipes, removed & checked N80 Evap system solenoid valve – OK on & off the car – both solenoid & pipes are completely clean – no sign of debris/dust/charcoal.

• Code cleared,

• Code returns within 1 mile of driving.

• Conclude GX 344 sensor faulty – not available separately so:

• Bought new genuine VW/AG N80/GX344 plus pipe assembly (all in one with quick connectors) & fitted. (£117)

• Code cleared

• Test drive of 15-20 miles All OK😀

• Check Engine light shows following morning 1 mile after restart.😡🤔

• Connect ODB reader & it shows one DTC. (P0441 again)

• Remove rear wheel & wheelarch liner, investigate activated charcoal canister & blow through all pipes.

• Remove canister & weigh – 1.700 Kg

• Check for weight of new one which is 1.330 Kg

• Conclude canister is contaminated, so order new VW/AG one. (£167) 01Sep2026

• LLL Parts take 5 days to dispatch an apparently "in-stock" item then DPD/Evri delays so part gets to me late Sep 11th (outside of my 10 working days free MOT retest)😠

• Fit new canister (after checking weight!) Sat 12th & arrange retest for today 14th Sept (I've dealt with this garage for MOT's for over 35 years so they squeezed me in)

• PASS MOT

The actual mechanical work is very straightforward, I could change sensors/pipes & canister in an hour now I know exactly what to do, but I have a nagging thought that only the canister needed replacing & my gx344 & N80 were fine - I know the N80 is certainly OK. It took hours of reading about these over complex modern petrol engines to find why & how to do the job, but the job was simple even at my advanced years (76☹️)

Anyway, wifey is now happy so I suppose it was £384 well spent - cheaper than a new cooker anyway😇

Under no circumstances whatsoever should 0.37kgs of sediment or whatever you wish to call it build up in 3 years and 23K miles, I have had 3 different family VWs, each well over 20 years old when scrapped and never had any problem like that, that canister is supposed to trap vapours, can only imagine that overfilling the tank at every refill might cause this in such a short period, it would be interesting though to see if all all new canisters are of equal weight.

Edited 10 hours ago10 hr by Johngerard

It will just be fuel in there, not sediment.

A pal of mine had a similar problem on a newish Octy, which was eventually fixed by dealer. They told him this:

" They fixed the engine light problem.

Apparently it is a known problem on some models, not usually on Octavia, where the vapour cartridge and pipe are undersized. The fix has been to replace these with the newer, larger, design.

Done under warranty."

I'd never heard anything like it.

Edited 3 hours ago3 hr by Breezy_Pete

It seems to me the trouble lies in two areas:

1 The canister should be sited so that no liquid petrol could reach it (short of a rollover!)

2 The logic in the ECU that the purge flow is "incorrect" is too picky - it's effect on engine performance is surely infinitesmal.

Personally I really can't see why these "vapours", which would be free of hydrocarbons after travelling through the charcoal canister anyway, shouldn't merely be vented rather than monitored & re- breathed.

The irony is that I only went to petrol to avoid the lunacies of modern diesel systems! It seems heads they win, tails they win🤔

18 minutes ago, JRL said:

Personally I really can't see why these "vapours", which would be free of hydrocarbons after travelling through the charcoal canister anyway, shouldn't merely be vented rather than monitored & re- breathed.

The idea is that the charcoal temporarily adsorbs the vapours, then releases them to be integrated into normal engine fuelling when engine is running. Lossless and clean.

Edited 20 minutes ago20 min by Breezy_Pete
Sp