Fix Bosch MAF Sensor: Repair & Troubleshooting

Hello fellow enthusiasts,

Regarding the Pierburg mass airflow sensor, Ulf has already shown us how to make something old new again.
What about Bosch mass airflow sensors? Assuming you have a Bosch mass airflow sensor...
'If a sensor consistently provides values that are simply too low (without any erratic or extreme fluctuations), and otherwise follows the expected performance curve, wouldn't it be possible to restore its functionality by using a simple, adjustable amplifier circuit? If this circuit were integrated into an adapter plug between the mass airflow sensor and its connector cable, the entire solution would be robust and neatly packaged. What do you think about this approach?'

I'm already working on an MC solution! Be patient! I'll be ready soon!

Hello Jörgs,

I guess I didn't catch that.

Check this out:

I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.

I'm currently working on a 90s4433 project. The pressure measurement should be working, but I'm still struggling with the speed measurement. According to Gremlin, the calculations aren't particularly exciting, and we'll also figure out the D/A conversion. However, I'm not using the STG data as planned, but rather connecting directly to the sensors. Give me a little more time. I have a new job, and I need more 'adjustment time' than I thought. Besides, I'm also working on the diesel mechanic MFA.

Marco wrote:

Suppose you have a Bosch mass airflow sensor. that simply provides values that are too low (without wild, complete failures, etc.), but otherwise follows the desired characteristic curve, then it should be possible to help this device perform better by using a simple, adjustable amplifier circuit.

Hi Marco,

Did you miss this?

I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.

While it hasn't been widely tested yet, it also hasn't been proven to be unusable.

Hi Ulf,



What else can I say? I missed that too, just like Jörg's attempts to create a fake LMM. Sorry! In any case, I'll definitely test that out, because my LMM is slowly but surely starting to fail. @Jörgs, are there any schematics available yet?

standard wiring for the microcontroller, nothing else.

Okay, so I'll apply a reference voltage of 2V to the AREF pin, and connect the boost pressure sensor to channel 0 via a 10:1 voltage divider. I'll also connect a separate pressure sensor for the ambient pressure to channel 1, also via a 10:1 voltage divider. The RPM will be connected to channel 2. That's all for now. The D/A conversion is still missing completely! Once the RPM is working, I'll take care of calculating the output voltage and implementing the conversion.
That would be the complete replacement!

As a pusher, I would also need to adjust the LMM voltage to channel 3.

But nothing has been documented yet! It needs to function properly on the evaluation board before I start creating the final design.

This is definitely the most minimal variant. I would be grateful for further suggestions regarding value inclusion. I think the intake air temperature would also be interesting. Let's see! It looks like I'm my own test subject!

Hi Jörgs,

There are plenty of ideas out there. Why not design it like the MFA replacement, essentially open source? If there's anything I can contribute to the development, I'm in!

It's supposed to become open source eventually. But I want to have something that actually works first, before I put it up for discussion!

There will be plenty more to do soon! We need to design, manufacture/have manufactured, document, and, of course, test the printed circuit boards! This applies to both projects!

@joergs

Great! / Awesome! / Fantastic!
...and allow yourself time for testing. Some Atmel chips have real EMC (Electromagnetic Compatibility) issues. I have a small circuit with a tiny12 that crashes on the vehicle's onboard network, even though it works fine under laboratory conditions .
Good luck!

@lucas

I've already developed the diesel engine control unit (ECU) quite a bit. I've also tested it twice in a car, covering approximately 350 km each time, and there were no stability issues! (It's based on the 8515 platform.)

What did you create with the Tiny?

The 'tiny' device should enable a simple 'one-tap blink function' – similar to what's found in new Audis, Mercedes, etc. This would cause the turn signal to blink three times with a single, short tap. Whether this is a useful feature or not is debatable.
The controller offers advantages through debounced inputs, adjustable timings, and a minimal number of external components – well, we'll see...

small circuit made with a tiny12, which crashes on the vehicle's electrical system even though it works fine under laboratory conditions .
Good luck!

Hey... automotive networks are the worst when it comes to electromagnetic compatibility (EMC). You really have to properly shield everything externally. And I mean everything, including the input/output (I/O) lines.

CU Gremlin.

@ Ulf

Hello Ulf,

'You've probably forgotten that I already had the EGR valve installed, and it's currently installed again. The goal is to reduce the amount of soot produced before the upcoming TÜV inspection by lowering the voltage.'

@ everyone

The experiments with MCs are appreciated, but the curve of the LMM (likely referring to a specific measurement or parameter) changes with age.
The idle value remains practically the same, the full throttle value decreases, and the device simply becomes 'unresponsive.'

As long as the original curve and the degraded curve are not precisely known, any attempt to convert between them is doomed to fail. Furthermore, this situation is constantly changing because the LMM (likely referring to a specific metric or parameter) is continuously deteriorating.
Simply amplify to the maximum output value, or, as I described, an op-amp can do that without needing an MCU. And if it gets worse, just keep increasing the amplification.

But still: have fun and good luck.

@garth

Yes, a regular amplifier can do that. The only thing is, as you mentioned, that you have to 're-align' it from time to time.

The microcontroller calculates the air mass based on sensor readings and generates a voltage for the engine control unit (ECU) via a digital-to-analog conversion. This means that even if the actual mass airflow sensor (MAF) signal were zero, an approximately correct air mass value would still be reported to the ECU, and this without any calibration. At least, that's the idea. In another variant, the air mass per stroke would be read from the engine control unit and the air mass to be reported to the ECU would be determined based on the engine speed. As mentioned, even if the MAF sensor were completely faulty, the system would still function almost as new! That's the theory! Practice will show whether this works or not.

garth.brooks wrote:

I'm sure you've forgotten that I already had the OP circuit installed, and I currently have it installed again.

Hi Garth,

No, I hadn't forgotten, but besides you, I haven't seen similar tests from anyone else.
Although I don't know your body shape, for me, one test pilot fundamentally doesn't represent a wide front (of testing) .