Thread: MAF resistance values

Could any body point me in the direction of a tutorial that may show me how to use a multimeter to check resistance..

I have tried a few you tube ones but i'm not sure I have done it correctly.

I have a reasonable digital multimeter.

Cheers

Originally Posted by onebob

Okay just back from JAYCAR with new meter and here's my MAF resistances.....

Pins 1-2 = 16.8 Kohm
Pins 1-3 = 21 Mohm
Pins 2-3 = 21 Mohm

16 Kohm across pins 1 and 2 is said to be a constant irrespective of MAF condition, So looking at the Mohm values and if an example of a dead one is 6.25Mohm and new ones are 34 Mohm then mine is still 'serviceable' i guess - am I correct?

onebob

Have been noticing that the D2 is not as "perky" as she once was and so decided to measure my MAF resistances and compare them with the last time i did it and that was 4 years and 5 months ago!! (see quote above)

Hope that forum members find the comparisons interesting although I gotta say that I'm not sure of what the actual ramifications of the readings are except for a simple mans conclusion that the ECU is probably not being fed accurate data which in the IT world translates as "garbage in = garbage out"

here are the results :-

Pins 1-2 = 16.8 Kohm
Pins 1-3 = 15 Mohm
Pins 2-3 = 15 Mohm

onebob

What's important if you want to make comparisons is to make measurements at the same ambient temperature and same multimeter cos the elements are temperatrure and voltage sensitive and if there is a noticeable difference between the temperatures where the measurements were made or the multimeter works on different voltage or even if it's battery is weaker or stronger than it was at a previous measurement the readings on the output side might be different....resistance mesurements on this kind of "active" devices are not the best way to diagnose them, eventually if you get to the circuit, isolate the sensing elements and measure only on those taking into account what i've already said about temps and voltage

Originally Posted by sierrafery

What's important if you want to make comparisons is to make measurements at the same ambient temperature and same multimeter cos the elements are temperatrure and voltage sensitive and if there is a noticeable difference between the temperatures where the measurements were made or the multimeter works on different voltage or even if it's battery is weaker or stronger than it was at a previous measurement the readings on the output side might be different....resistance mesurements on this kind of "active" devices are not the best way to diagnose them, eventually if you get to the circuit, isolate the sensing elements and measure only on those taking into account what i've already said about temps and voltage

Thanks SF for your input, for the record both times the MAF unit was out of circuit removed from the vehicle and taken indoors (into controlled atmosphere) and measurements taken using the same multimeter. Certainly not as strict as you advise but from a before and after broadbush comparison there is an obvious trend towards ultimate failure. Time for a new one i reckon

Yes, i've always been under the impression that the MAF "wears" out in time and will start giving erratic readings sooner or later... which is valid for any sensor IMO

Originally Posted by sierrafery

Yes, i've always been under the impression that the MAF "wears" out in time and will start giving erratic readings sooner or later... which is valid for any sensor IMO

Noted!!

I went for a 4 hour drive today in hilly country and the roads were a mix of black top and dirt but on all the D2 was noticeably down on power. The driving experience was the same as before I had the chipped (upgraded) ECU fitted 6 years ago. Throttle response is fuzzy and it seems to me that the TD5 is under fueling, also I noted that the EGT's were running lower than normal.

As an experiment I uplugged the MAF and drove for an hour but the engine reponse was the same - not better - not worse! So I guess the MAF is still functioning but supplying inaccurate data.

I'll have a new MAF this week but should I change the MAP sensor as well?

IMO if you can afford putting a new genuine sensor instead of an old one is a good move anyway no matter which one, even the sensors can get "tired" after a prolonged exposure to that unfriendly environment.... i've replaced the ECT sensor some time ago as the old one was still the original so i thought it's time for it to ''retire'' ... surprise, the new one was reading 4* higher at fully warmed engine(92) which reduced slightly the fuel consumption.

Originally Posted by onebob

Noted!!

I went for a 4 hour drive today in hilly country and the roads were a mix of black top and dirt but on all the D2 was noticeably down on power. The driving experience was the same as before I had the chipped (upgraded) ECU fitted 6 years ago. Throttle response is fuzzy and it seems to me that the TD5 is under fueling, also I noted that the EGT's were running lower than normal.

As an experiment I uplugged the MAF and drove for an hour but the engine reponse was the same - not better - not worse! So I guess the MAF is still functioning but supplying inaccurate data.

I'll have a new MAF this week but should I change the MAP sensor as well?

After some further research I learned about how MAFs actually worked and how to test them and discovered that it's all about voltage output so I tested the voltage output from the MAF sensor. It is said that the output should be 1.95V at idle and rise with engine speed to a maximum of 5V. The result for mine was 1.88V at idle rising to max of 3.70V and then it starts to fall away at 3000RPM. Clearly the ECU is receiving erroneous data and is a likely contributor (and maybe not the only one) for the power loss I'm experiencing recently.

Here's the link to a vid i recorded at the time...
https://youtu.be/rLJ1BxZ1LTw

And the link to the tutorial that was the main source of my information that I took on trust as being accurate and reliable.
https://www.youtube.com/watch?v=JzrP1saTm9A

Now I've demonstrated to myself that the MAF is out of specification it'll easier to part with the $$'s.