LMM and AGR Off: What Happens? (Under 3000 Miles)

Hello,

I'm new to this forum. I probably have the well-known mass airflow sensor (MAF) problem, and the tip about using a diode as a MAF replacement is really valuable (unfortunately, I don't know who came up with it, but thank you very much!).

'I have an ALH engine that, for some time now, has been reducing the fuel injection amount intermittently when overtaking and on the highway, even with the accelerator pedal fully pressed (the instantaneous fuel consumption displayed on the MFA jumps between 8l and 13l). This results in a wavy acceleration pattern, which, according to other users in this forum, indicates a faulty mass airflow sensor.'

I have now bypassed the LMM (lambda sensor) with the aforementioned diode, and that has eliminated the error (well, it's probably going to be expensive...). To prevent the EGR system from causing the valve to fully open due to this issue, I also disabled the EGR system. However, I wanted to make as few mechanical changes as possible, so I simply disconnected the connector at the EGR solenoid valve; the entry in the error memory isn't that important to me right now.

'Has anyone had experience with this type of EGR deactivation? I'm now experiencing a strange phenomenon where the car feels sluggish up to around 3000 RPM, but then suddenly accelerates like crazy once it exceeds that mark. The yellow warning light in the instrument cluster doesn't illuminate at any time.'

- Perhaps there is already an electronic monitoring system for the connector at the EGR magnetic valve in my ALH model year 2000?

- At what engine speed does the partial load range end, and therefore is the EGR system generally deactivated? Could it be 3000 RPM?

- Can you always identify 'Notruf' (emergency call) by the yellow indicator light, or are there also variations where it is not displayed?

It would be nice if someone could comment on this.

Best regards,
Robert.

robertf wrote:

Perhaps there is already an electronic monitoring of the connector at the EGR magnetic valve in my ALH model year 2000.

Hi Robert,
The EDC essentially monitors the resistance at the solenoid valve connector, but I believe it has been doing so since the first generation of TDI engines.
This then also leads to the error message "Solenoid valve for EGR..."

Quote:

At what engine speed does the partial load range end, meaning when is the EGR system generally closed? Could it be 3000 RPM?

As the name "partial load" suggests, it also depends on "how much throttle you give it." Therefore, a specific speed limit cannot be determined.

- Can you always identify a "Notfall" (emergency) mode by the yellow indicator light, or are there also variations where it is not displayed?

Quote:

Unfortunately, I don't know that.

However, there is an area where the AGR (Abgasrückführung system) is active, and this area is also speed-dependent. Around 3000 RPM is approximately where the AGR shuts off. However, this doesn't affect full-throttle acceleration because you don't have any AGR function at that point anyway!

Hi Ulf and Ben1972!

Thank you for your comments! I have now re-enabled the faulty MAF sensor (the EGR valve is still without power) and I'm a little wiser: The 'limp home' mode (or whatever it is) with low fuel injection rates up to 3000/min is gone, which means that the disconnected EGR valve isn't the cause of it, but rather my diode acting as a MAF sensor replacement!

Could it be that my engine is already 'smart' enough to react to these implausible, very high mass airflow sensor (MAF) values at speeds below 3000 RPM by entering some kind of emergency mode?

'There are some people in this forum who are using a diode as a replacement for the mass airflow sensor (MAF). What engine control unit (ECU) do you have that makes it work so well for you? Could it be that the diode trick only works correctly with the 1Z engine?'

Best regards,
Robert.

robertf wrote:

i.e., the removed EGR valve is not actually to blame, but rather my diode acting as a replacement for the mass airflow sensor (MAF)! Could it be that my engine is already "smart" enough to react to these implausible, very high mass airflow sensor (MAF) values at speeds below 3000 RPM by entering some kind of emergency mode? Here in the forum, there are some people who use a diode as a replacement for the mass airflow sensor (MAF). What is your engine code (MKB)? How do you manage to get it working so well? Could it be that this "diode trick" only works correctly with the 1Z engine?

Hi Robert,

Okay, it also works with the AFN (97).

I've included a scenario similar to the one you experienced in an article about Large Language Models (LLMs), although I wasn't exactly sure which engines might behave that way.

I believe Georg may have once published this technique after experimenting with it using his own ASV... ?

Hello Ulf,

der Fachartikel von Dir war auch meine beste Quelle bei dem ganzen Thema. Absolutely fantastic!

However, I thought I would recognize the emergency exit by the yellow spiral, but apparently, there's also something like a 'partial' emergency exit.

'At least now we know that with the ALH engine, you have to make sure the RPM doesn't drop below 3000. Otherwise, it drives great with the diode; I even think it pulls better than ever before! Maybe my mass airflow sensor (MAF) has been faulty all along. After all, I've only got about 50,000 km on the odometer, which isn't that much for it to fail already, is it?'

Best regards.
Robert.

Bosch mass airflow sensors don't last very long.

Best regards, WarLord.

Hello,

I can relate to Robertf's experience that...

mkb alh
and the diode 1N4148 instead of the original component, which the control unit detects. An entry "MAF sensor - implausible signal" will appear in the fault memory, and the control unit calculates a substitute value of 550 mg of air per revolution.

I tested it myself on a Skoda Octavia ALH. While a test LED bulb didn't cause this error, the driving behavior was unacceptable because there was very little acceleration below 1300 rpm, followed by an abrupt surge of power.
The diode trick is not recognized by ASV.

best regards, georg