P0402 and P1A58 codes some wierd going on here!

Runtmp

Member
Joined
Jul 24, 2020
Location
California
TDI
11 Golf MK6 TDi
So i got a 11 golf tdi with 49800miles on it.
My dpf light comes and goes(usually on when i start the car but goes away after 10min). Check engine light is on too. The car in Drive or reverse would not go above 1000-1100rpm. Dealer wont look at it since i have put GTI muffler on it even though its still under warranty until Sept 2023, and still want to charge me a kidney and a liver for exhaust replacement when they cant guarantee it'll fix the problem. Vcds comes up with 2 codes p0402 and p1a58 which has to do with excessive flow. So I took off the dpf, intake manifold, egr filter, egr valve, egr cooler, throttle body and have cleaned them very nicely. I cleaned it with this chemical that is used to clean commercial oven burners. After soaking everything for 2 days the solution looks like oil with ash, its very dark....could probably use it as engine oil.

So after everything was cleaned out and put back together still have the same problem. While in park or neutral it reaches 2500rpm easily but in drive or reverse wont go past 1000rpms. Right before the codes appeared i had the fuel system replaced by dealer under warranty because of shavings in fuel filter. And i began to notice that throttle response had a lag.

Im stuck and dont know what else I should check or do. Any suggestions or comments will be greatly appreciated.

Thank you,
Tim
 

Runtmp

Member
Joined
Jul 24, 2020
Location
California
TDI
11 Golf MK6 TDi
@Lightflyer1 thank you for responding. I've been arguing with the dealership for the past month over this, and waiting for response from VWoA.
I replaced the MAF sensor, it helped but still underboosting cleared codes but they came back
 

Lightflyer1

Top Post Dawg
Joined
Sep 13, 2005
Location
Round Rock, Texas
TDI
2015 Beetle tdi dsg
What exactly was done when the dealer replaced the fuel system? If that wasn't done correctly and completely, that could be a possible issue.
 

Runtmp

Member
Joined
Jul 24, 2020
Location
California
TDI
11 Golf MK6 TDi
The fuel filter had metal shavings, since its covered under warranty the dealer replaced the entire fuel system. Im going to replace n75 valve and if that dont help ill be going after the actuator next to the turbo. Also the mpg is bad I average about 25mpg combined. If I drive it hard the mpg was worse, and theres a smell of burning oil.
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
You first need to do a login and reset for the DeNOx catalyst, you cannot "clear" that DTC until you do.

Second, if there was any soot (and "black", of any kind) in the low pressure EGR filter pipe, the EGR cooler, or anything in the exhaust post-DPF, then your DPF is bad and needs to be replaced.
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
If there is any soot inside aft of the DPF, then yes, it is cracked/bad and needs to be replaced. Very common. There is a TSB about it even before Dieselgate, they are much worse now. The dealer knows this, they cannot possibly be that stupid. They should stock all of the parts on the shelf, ours does. I had three of them in here last week alone.
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
Neither of your DTCs show anything to do with underboost. The underboost DTC is typically a P0299, and in some cases some form of MAF-related DTC may also show up, like a P0101 or 103.
 

Runtmp

Member
Joined
Jul 24, 2020
Location
California
TDI
11 Golf MK6 TDi
@oilhammer thank you for your help! It is more than greatly appreciated. I got a tdi muffler earlier today, going to take the gti muffler off put it on a the tdi one back on. Also got an appointment at a different dealership to have the dpf replaced. Will keep forum posted about what the outcome will be
 

Runtmp

Member
Joined
Jul 24, 2020
Location
California
TDI
11 Golf MK6 TDi
Just got the car back from dealer the EGR was replaced under warranty. The egr was sticking badly. But after about 30min of driving I got a p0401 code. Bringing the car back in tomorrow for more warranty coverage.
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
I have never, ever, even once, seen an EGR valve itself cause a P0401 EGR flow DTC on a CJAA TDI. It is ALWAYS the EGR filter tube plugged up, which is ALWAYS a symptom of a cracked DPF. I have also never seen a P0402 on on these, either.

In any event, as stated previously, there is a TSB for this, it is SUPER COMMON, and if your tailpipes are sooty, your DPF is bad. Period.
 

Runtmp

Member
Joined
Jul 24, 2020
Location
California
TDI
11 Golf MK6 TDi
I have stated what you @oilhammer have told me about the DPF is bad or cracked, but they basically said they're techs will find the problem and fix it, so now they're back at it.
 

Runtmp

Member
Joined
Jul 24, 2020
Location
California
TDI
11 Golf MK6 TDi
So now they're saying they can't replace the dpf because the MAF was replaced and because of that, the warranty is voided. Talked with manager and explained to him if he looks at the VW of what's covered under the emissions warranty it says nothing about MAF. He said he'll get back to me so waiting to hear back what they'll say now
 
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