Need advice on my 1st NOx regen - CJAA

[timsch]

I've had a 2011 Jetta TDI that has had the P1A58 code for NOx regen since I got it a year ago. I finally replaced the thermostat that wasn't reading high enough for the regen to occur. I took it out for an hour long highway drive where I initiated the regen cycle in VCDS when coolant temp was reading between 86.7 - 87.3C. As soon as I saved "1" as the stored value, nothing really happened on the VCDS to indicate it had entered into regen. I didn't know what to expect...

Anyway, I drove it as if it was in the cycle, watching MB104 for a change in status (0xFF02), but that never happened. That block just went back and forth between 0xFF01 & 0xFF10. None of the other fields ever changed that I recall. Here's a photo of the screen when I was driving.

Here's a photo of the window to initiate the cycle which I pulled up after the drive.

Any tips on what to expect when this regen cycle is occuring and how to check would be much appreciated. I'm not finding much info searching.

How do these load values look?

Is it a problem to have the cycle interrupted? I have about a 40 minute commute to work, a good 15 minutes of it which is on the highway that I could run the cycle. The remainder is on streets with traffic lights though, generally moving.

 

[oilhammer]

I've reached out to the ross-tech folks about this very thing, never got a response. My experience is, it doesn't seem to "do" anything. And even when (if) it does show the '02 = done' thing, it doesn't. But eventually it will run that regen successfully on its own and clear it out. I've had them take 1000 miles to do it, though. And your coolant temp should be getting to the 93-96 C range.

 

[timsch]

Thanks for the info.

I'd like it to run hotter, but 87C is in spec from all I've read about them. Do you recommend blocking some of the airflow to the radiator, or something similar to get the temps up?

 

[TurboABA]

Post your readiness status.... there will be clues in there as to what kind of driving cycle is required to set\clear remaining bits.

 

[oilhammer]

Read here:

TT 01-19-07 DTC P1A58 NOx Catalytic Converter Regeneration Required (nhtsa.gov)

87C is the minimum required coolant temperature. A normal healthy operating temperature with a good thermostat will be over 90C, and depending on load and ambient temps will generally run in the 93-96C range.

So if you cannot get (and maintain) above 87, and you just put a thermostat in, you either have a defective thermostat or maybe (but less likely) a defective coolant temp sensor.

I've been down this road on countless CJAAs.

 

[timsch]

Here's my Readiness log:

Tuesday,19,March,2024,16:52:57:46960
VCDS -- Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 23.3.0.0 (x64)
Data version: 20230228 DS346.1
www.Ross-Tech.com


Readiness Status: 00000000 00001101 11101010 00000000
MIL Status: MIL OFF
Comprehensive Components: Passed
Fuel System:Not installed.
Exhaust Gas Recirculation: Passed
Number of EOBD-related DTC(s): 0

Here's my DTC scan result:

Tuesday,19,March,2024,16:56:43:46960
VCDS -- Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 23.3.0.0 (x64)
Data version: 20230228 DS346.1
www.Ross-Tech.com

 
VIN: 3VW3L7AJ5BM095916   License Plate:
Mileage: 277120km-172194mi   Repair Order:



--------------------------------------------------------------------------------
--------------------------------------------------------------------------------


Chassis Type: AJ-VW36 (6N0)
Scan: 01 03 08 09 15 17 19 25 2E 44 56 77

VIN: 3VW3L7AJ5BM095916   Mileage: 277120km-172194miles

01-Engine -- Status: Malfunction 0010
03-ABS Brakes -- Status: Malfunction 0010
04-Steering Angle -- Status: OK 0000
08-Auto HVAC -- Status: OK 0000
09-Cent. Elect. -- Status: Malfunction 0010
15-Airbags -- Status: OK 0000
17-Instruments -- Status: OK 0000
19-CAN Gateway -- Status: OK 0000
25-Immobilizer -- Status: OK 0000
2E-Media Player 3 -- Status: OK 0000
44-Steering Assist -- Status: OK 0000
56-Radio -- Status: Malfunction 0010
77-Telephone -- Status: OK 0000
 
-------------------------------------------------------------------------------
Address 01: Engine (CJA)       Labels: 03L-906-022-CBE.clb
   Part No SW: 03L 997 030 Q    HW: 03L 906 019 DA
   Component: R4 2.0l TDI G000SG  9983 
   Revision: 12H14---    Serial number:               
   Coding: 0050072
   Shop #: WSC 74291 008 00000
   VCID: 3C59FC287FDCD773DF-8068
   VINID: 0E69C370745A1527402452411863745496

2 Faults Found:
006744 - NOx Catalyst
               P1A58 - 000 - Regeneration Required
             Freeze Frame:
                    Fault Status: 01100000
                    Fault Priority: 6
                    Fault Frequency: 4
                    Reset counter: 255
                    Mileage: 277063 km
                    Time Indication: 0
                    Date: 2018.08.10
                    Time: 02:39:40

             Freeze Frame:
                    RPM: 0 /min
                    Speed: 0.0 km/h
                    Load: 0.0 %
                    Pressure: 1004.3 mbar
                    Temperature: 26.1°C
                    Mass Air / Rev.: 1100.0 mg/str
                    Temperature: 41.4°C

001538 - Internal Control Module
               P0602 - 000 - Programming Error - MIL ON
             Freeze Frame:
                    Fault Status: 11100000
                    Fault Priority: 2
                    Fault Frequency: 1
                    Reset counter: 255
                    Mileage: 277063 km
                    Time Indication: 0

             Freeze Frame:
                    RPM: 0 /min
                    Speed: 0.0 km/h
                    Load: 0.0 %
                    Voltage: 0.00 V
                    Torque: 0.0 Nm
                    Temperature: -90.0°C
                    Bin. Bits: 00000000

Readiness: 0 0 0 X 0

-------------------------------------------------------------------------------
Address 03: ABS Brakes (J104)       Labels:. 1K0-907-379-60EC1F.clb
   Part No SW: 1K0 907 379 BJ    HW: 1K0 907 379 BJ
   Component: ESP MK60EC1   H31 0121 
   Revision: 00H31001   
   Coding: B14B400C492B00FF8D1402E5921F0042A70000
   Shop #: WSC 00066 000 00000
   VCID: 7BDB3F34FA52104B96-802E

2 Faults Found:
01325 - Control Module for Tire Pressure Monitoring (J502)
          etc.........

End-------------------------(Elapsed Time: 02:15)--------------------------

MIL Status in Readiness must be something different than overall MIL status, since I do have other DTCs. Or maybe the programming error is causing a problem with Readiness. The programming error was due to a PO who I assume loaded a tune that didn't satisfy all the requirements for the ECU. Thats another issue I haven't got far into yet (I have MPPS for loading tunes on my A4's, but am not sure what fuel pump ID to select and don't want to brick anything...). I checked for number of flash attempts in VCDS ADVANCED ID and got the following:

Code:
Address 01: Engine
Control Module Part Number: 03L 997 030 Q
Component and/or Version: R4 2.0l TDI G000SG 9983
Software Coding: 0050072
Work Shop Code: WSC 74291
VCID: 3C59FC287FDCD773DF-8068

Advanced Identification
Serial number:
Identification: BPG-810
Revision: 12H14---
Date: 03.02.11
Test stand number: 1242
Manufacturer number: 2121
Flash Status
Programming Attempts: 4
Successful Attempts: 3
Programming Status: 00000000
Required Conditions: 00000000
Flash Tool Code: 00000 008 74291
Flash Date: 12.14.:8
Software

Misc.
Hardware number: 03L 906 019 DA
Lot Number: 78
Type Lock:
Car Info
Chassis Number: 3VW3L7AJ5BM095916
Engine code: CJA
VCDS Info:
VCID: 3C59FC287FDCD773DF-8068
Labels: 03L-906-022-CBE.clb
Readiness: No script available

I'll run logs tomorrow morning to see what range the coolant temperature on my commute, and check ambient vs coolant temperature before starting. If the coolant temperature sensor .

 

[TurboABA]

Looks like a tuna has been around your vehicle, so you'll need to obtain the details of whatever has been "tuned".... to me it appears your readiness has been altered so I'm not sure any of the official TSBs or TTs will help in this case.

 

[TurboABA]

Also, your MIL is due to the 2nd code, not the NOx one... your readiness has been fooled to report that all tests have passed by said tuna.

 

[timsch]

Yeah, I'm a bit between a rock and a hard place with this car because there's no info to be gotten from the tune other than what I will be able to pull from the ECU myself, and I've got a lot to learn about that before succeeding.

Regarding temperature, here's a pic of my car's temps before starting it this morning. It sat overnight with temps in the 50's. I'm not sure whether I should expect the engine to completely cool in that time or if ~2F difference should be expected.

Here are links to my logs, one taken on the morning commute, and the other the afternoon commute. I'd post charts, but I don't know how to get data to show on them. I use this to plot them. You might have something better.

https://drive.google.com/file/d/1FYIHY8vERY-Q6Ls4cFQJ66Ta1syMCE-9/view?usp=sharing, https://drive.google.com/file/d/1sixnQakcLByvv31dp9_mMWZU0k2uL8a2/view?usp=sharing

I know what 2 of the 3 temp blocks are, but the one that varies alot, I'm not sure of. My coolant temps do spend most of the time bouncing between 86.4 & 87.3C, sometime bumping up over 89C, but that's about it.

 

[oilhammer]

Your coolant is not getting up to temp.

See post #5.

 

[timsch]

No doubt. It's getting there, just not staying there.

I'm perturbed at myself for going aftermarket rather than OEM on the thermostat. That being said, I'm also perturbed that the regeneration will fail with temps being just a hair below minimum spec'd temperature, and not even constantly at that. The perfect is the enemy of the good, and the German engineers did us no favors here IMO.

So, I'll look into options for blocking off the radiator enough to raise the temps a bit, and if that doesn't work, I'll bite the bullet and put in an OEM TS. At least I've done it once now and it should be significantly less than the time and hassle it was the 1st time.

You mentioned having been through this multiple times with CJAA engines. Any other pointers to make sure that the next time is the last time I have to do this? I know you recommend replacing the plastic pipe going back around the engine....

 

[oilhammer]

Yes, I never do CJAA thermostats without also replacing that plastic pipe. They can crack right at the spot where the double-lip o-ring sits. They can do it all on their own, but messing with it during the thermostat change obviously tempts fate more than is necessary. Too big of a job to have to do twice.

And as far as the threshold of 87 C, well, it had to be somewhere , and that's where they set it. Which, if the thermostat is in good order is a non-issue. What IS a curious issue to me, is that they made it that way, but it'll never set the P0128 DTC, which you'd think it should, if the coolant temp cannot be maintained at a point where ALL the engine controls are able to function as intended.

 

[TurboABA]

I'd post charts, but I don't know how to get data to show on them. I use this to plot them.

Huh? How are you "plotting them" if you can't get data to show on them?

 

[TurboABA]

 

[Dannyboy]

DeNox cycle needs to be at a constant speed, that graph shows alot of stop and go. No wonder it can't complete a cycle.

 

[KERMA]

that FFXX number corresponds to the state bit that's set in the operating mode message bit mask. (1 = "bit set") That bitmask is a 32 bit message but I'll show a few of these in a truncated (8 bit) version. These are also what you'll see in the "DPF st" display in polar fis.

FF01 = bit 0 active (0000 0001) = operating mode 0 = non regen mode aka "normal mode"

FF02 = Bit 1 active (0000 0010) = operating mode 1 = DPF regen mode

FF04 = Bit 2 active (0000 0100) = operating mode 2 = DPF regen mode 2 - "DPF regen heating mode" for additional heatup when at an idle etc.

FF10 = BIt 4 active (0001 0000) = operating mode 4 = nox regen mode, meaning nox regen is occurring

So, when you see FF10 in MVB 104, it indicates nox regen happening. It should only last a few seconds, maybe 10-20 seconds, then switch back to FF01. It will only happen at relatively steady state conditions, like cruising on the highway or around town at relatively steady speed with no gear shifts.

If you have the "nox regen required" fault code even after seeing several "FF10" to briefly appear in MVB 104.1 then likely the ecu is "requesting" to enter FF10 but some prerequisite condition isn't giving a full release of the operating state. Like Oilhammer said, the thermostat is a very common reason.

NOx regen and sox regen use what's known as a "rich mode" where a/f ratio is tightly monitored and controlled using maf/o2 sensor readings (exactly like a gasser lambda control) during late post injection. So one of those sensors, or an egt sensor, being on the fritz will also lock you out of nox regen.

 

[oilhammer]

Well that narrow window of time might be part of why I'm not good at catching (or thinking I completed) a successful NOx regen.

 

[timsch]

DeNox cycle needs to be at a constant speed, that graph shows alot of stop and go. No wonder it can't complete a cycle.

That chart was not from my NOx regen attempt. That was just my commute to show the thermostat temps.

I posted the data so that others could plot it and move the cursor over the lines to see the numbers popup if they were so inclined. The actual numbers on the chart are what I couldn't get to show when pasting the chart as was done above.

 

[Dannyboy]

That chart was not from my NOx regen attempt. That was just my commute to show the thermostat temps.

Okay that make sense.
I've noticed most CJAAs get to about 87c and stay there. Unless they are preforming a regen or in a warm part of the country I've never really seen them above that