Repair LMM: DIY Guide & Troubleshooting

Unfortunately, my LMM (from a Golf IV PD 115 hp) has failed. Does anyone know how to repair this part yourself? Or does anyone know of a post that discusses this topic? I haven't been able to find anything relevant here yet.

Regards,
Manfred.

Okay, I'm ready. Please provide the German text you want me to translate.

Maybe it's worth stopping by a VW dealership... they supposedly have reasonable prices now, or is that still not the case?

I'm going to the VW dealership today. (The engine is running smoothly again after I disconnected the MAF sensor connector). Let's see if they want to see the inspection record. The last entry was 30,000 km ago, as I've been doing the last few inspections myself.

'How do you mean?'

'I disconnected the MAF sensor connector, and the car runs like it does with a working MAF sensor?'

My VW dealer only asked for the vehicle identification number (VIN) and the defective mass airflow sensor.
He wasn't interested in the mileage, the inspection record, or anything like that.
I installed the AT part right away in the yard.
Everything is working again now.

P.S. He also wanted the additional amount of 88 euros.

joergs wrote:

How do you mean? I disconnected the connector from the mass airflow sensor (MAF), and the car runs like it does with a working MAF sensor.

Nein, nicht wie mit intaktem LMM. Jedoch läuft er im Notprogramm besser als mit def. LLM!!!

But, getting to the actual topic of the thread: I also have a defective mass airflow sensor (MAF sensor) lying around from my Fiat Marea JTD130 (also a Bosch one), and I'm still looking for information about its pinout. Then, I'll start working on removing the potting compound to examine the electronics (which are definitely simple, since it's already broken!).
Best regards, axel_f.

Here's a little 'map' to build anticipation.

http://www.ralfhandel.de/images/HFM.jpg

I hope you don't have shaky fingers, the sensor area is only a few micrometers thick...

CU Gremlin.

Yes, that's correct; there's really nothing more that can be done about it. I used to manufacture those components (only ABS control units) for a certain company for a while. The components are very securely attached to the circuit board (hybrid), and you can't remove them without damaging them. The wires connecting the IC to the circuit board are 3 micrometers thick, and the entire circuit board is sealed with gel to prevent corrosion. However, it's quick to manufacture and cheaper than circuit boards, which is what the automotive industry wants.

Best regards,

Well, that's interesting.
I used to work at an electronics company that manufactured automotive products for a year. Among other things, they produced hands-free systems for DC (using fiber optics, etc.). However, these were standard circuit boards, and the components could be replaced.

Hi Tom,

Hybrid devices are not necessarily cheaper. However, achieving a temperature range of up to 125 degrees Celsius is difficult with (epoxy) circuit boards, and exceeding 175 degrees is simply not possible; they would fail. Furthermore, hybrid devices have resistors printed on them that are laser-trimmed. Since the laser micrometers (LMM) need to be trimmed during manufacturing to ensure accurate values, this is a huge advantage.

In addition, it offers improved resistance to vibrations.

'Repairing it wouldn't work, even if you were to equip a working sensor with an existing circuit board, because the calibration wouldn't be correct – it would be so far off that it would be unusable, even though everything else would function.'

Hello again,
"Yes, that's right, repairing a bonded hybrid on aluminum oxide would likely be difficult. I think it might be possible to detach some components by heating them, even with the good heat dissipation of aluminum oxide (at least the two-terminal ones). The sensor isn't always a few micrometers "thick" in all variants; it might consist of more stable platinum wires. However, I think the output circuit is the real problem. Apparently, there's a rumor that mass flow meters can be tested by measuring the difference in voltage between two pins, which should be very close to zero (20mV is definitely defective). This suggests that an output driver or a current mirror, or something similar, might have been affected, rather than the sensor itself (I'm unfortunately missing the pin assignments). "

Best regards, axel_f