Post Injection 3 consistently showing 1.0–1.3 mg/str – DGTE / Delphi DCM6.2
Hello everyone,
I would appreciate some technical insight into the Post Injection 3 parameter displayed by the VAG DPF application.
Vehicle and ECU information:
- Vehicle: 2019 SEAT Ateca 1.6 TDI DSG
- Engine code: DGTE
- ECU: Delphi DCM6.2
- ECU software number: 04L906056TG
- Software version: 7226
- Hardware number: 04L907445G
- ECU identifier: D11EV_ECM16TDI030
- Current mileage: approximately 93,000 km
1. Post Injection 3 behaviour at idle
Even when the engine is fully warm and idling, Post Injection 3 frequently shows approximately 1.21–1.31 mg/str.
Post Injection 1 and Post Injection 2 remain at 0.00 mg/str.
This behaviour is not limited to active DPF regeneration.
2. Post Injection 3 behaviour while driving
I have also monitored the parameter while driving, and its behaviour is particularly interesting:
- During normal driving with the accelerator pressed, Post Injection 3 generally shows approximately 1.21–1.31 mg/str.
- When I release the accelerator and the vehicle enters engine braking/deceleration, the value drops to 0.00 mg/str.
- As the vehicle slows down further, without pressing the accelerator again, Post Injection 3 becomes active again and returns to approximately 1.21–1.31 mg/str.
- This behaviour occurs regardless of the DSG gear.
- Post Injection 1 and 2 remain at 0.00 mg/str during these observations.
The value appears to change according to the engine operating condition rather than being associated exclusively with DPF regeneration.
3. Observations from actual driving
I recorded two screenshots during my morning commute:
At 92,992 km:
- Post Injection 3: 1.00 mg/str
- Post Injection 1 and 2: 0.00 mg/str
- Calculated soot mass: 14.07 g
- Distance since last DPF regeneration: 102 km
- Regeneration duration: 0 minutes
- DPF inlet gas temperature: 207 °C
At 93,000 km:
- Post Injection 3: 1.23 mg/str
- Post Injection 1 and 2: 0.00 mg/str
- Calculated soot mass: 14.47 g
- Distance since last DPF regeneration: 109 km
- Regeneration duration: 0 minutes
- DPF inlet gas temperature: 192 °C
Therefore, Post Injection 3 is not simply appearing during an active DPF regeneration.
4. Fuel consumption
The vehicle has no noticeable drivability problems.
- No fault codes currently present.
- Engine runs normally.
- No noticeable loss of power.
- No abnormal smoke.
- No obvious injector-related symptoms.
However, compared with other vehicles equipped with the same 1.6 TDI engine, my vehicle consumes approximately 1 litre/100 km more fuel under comparable driving conditions.
I am wondering whether the persistent Post Injection 3 reading could be related to this difference in fuel consumption.
5. Questions for the developer and experienced users
I found the previous forum explanation stating that Post Injection 3 is used less frequently during normal driving, while all three post-injections can be used during DPF regeneration.
This is why my observations are confusing.
Could you please clarify:
1. What exactly does the Post Injection 3 value represent in the VAG DPF application?
2. Is it the actual commanded quantity of the third late post-injection, or a calculated/requested value?
3. Can Post Injection 3 legitimately remain around 1.0–1.3 mg/str during normal driving and warm idle, outside active DPF regeneration?
4. Can this behaviour be related to NOx catalyst desulphurisation or another emissions-control strategy?
5. Has the Post Injection 3 parameter been fully verified on the DGTE engine with Delphi DCM6.2 software version 7226?
6. Could there be a PID/CAN parameter mapping difference on this ECU software version?
7. Is there any known reason why this parameter becomes zero during engine braking and returns while the vehicle is slowing down?
I would particularly appreciate clarification from the application developer regarding the exact ECU signal and its interpretation.
I am not assuming that the reading indicates a fault. I simply want to understand why Post Injection 3 behaves this way on my vehicle and whether it could explain the approximately 1 L/100 km higher fuel consumption.
Thank you in advance for your help.
Post Injection 3 consistently showing 1.0–1.3 mg/str – DGTE / Delphi DCM6.2
Re: Post Injection 3 consistently showing 1.0–1.3 mg/str – DGTE / Delphi DCM6.2
I've always owned TDI cars with BOSCH ECUs, so I'm not sure we can trust in my experience for a DELPHI ECU engine.
Anyway, in my logs I've always seen the 3rd post injection active during the regeneration only. The other 2 was active (sometimes) also in normal running instead.
I checked in my VAG documents and I found those details about TDI and DPF system.
Consider that those come from not so recent documents because they refer to the first EA288 TDI family engines like CLHA,CRBC, CAYC.
These paragraphs are aligned with my experience confirming the third injection related to the regeneration process with the purpose to send uncombusted fuel in the DPF, where it will burn.
But I repeat, don't consider these information as a statement because there's no clear link to your engine code and we know how many engine variants VAG created in its history.
A possible reason could be a new approach for the emissions or the engine noise that involves the third injection in more recent engines only.
Moreover, before to consider it an issue for your engine, I suggest to double check the app values with another diagnostic software, even better with an official VAG software.
Of course a direct experience from another DGTE user would be very useful.
Anyway, in my logs I've always seen the 3rd post injection active during the regeneration only. The other 2 was active (sometimes) also in normal running instead.
I checked in my VAG documents and I found those details about TDI and DPF system.
Consider that those come from not so recent documents because they refer to the first EA288 TDI family engines like CLHA,CRBC, CAYC.
From SSP442 "The 1.6 ltr. TDI Engine with Common Rail Injection System" > Common rail fuel injection system
Very small quantities of fuel in the pilot injections are followed by the main injection and then several secondary injections for active regeneration.
While the pilot injections make the rise in pressure in the combustion chamber more constant and thus reduce the combustion noise, the secondary injections are intended for exhaust gas treatment. Together with the powerful control unit and the injectors with small tolerances, the common rail injection system clearly reduces consumption and emissions. At the same time, it increases the engine power and allows quieter running.
From SSP514 "The New EA288 Diesel Engine Family" > Actions of the engine control unit to raise the exhaust temperature during active regeneration
- The intake air supply is regulated via the throttle valve module.
- Shortly after “retarded” main injection, one or two post-injections are introduced to increase the combustion temperature.
- Further post-injection is introduced long after main injection. The injected fuel does not combust in the cylinder, but evaporates in the combustion chamber.
- The uncombusted hydrocarbons contained in the fuel vapour are oxidised in the oxidising catalytic converter. The heat that is generated during this process reaches the particulate filter via the air flow and increases the exhaust gas temperature upstream of the particulate filter to approximately 620 °C.
- For the calculation of the injection quantity for the retarded post-injection, the engine control unit uses the signal from exhaust gas temperature sender 3 G495.
- The charge pressure is adapted so that during regeneration torque does not change noticeably for the driver.
These paragraphs are aligned with my experience confirming the third injection related to the regeneration process with the purpose to send uncombusted fuel in the DPF, where it will burn.
But I repeat, don't consider these information as a statement because there's no clear link to your engine code and we know how many engine variants VAG created in its history.
A possible reason could be a new approach for the emissions or the engine noise that involves the third injection in more recent engines only.
Moreover, before to consider it an issue for your engine, I suggest to double check the app values with another diagnostic software, even better with an official VAG software.
Of course a direct experience from another DGTE user would be very useful.