Air Flow Sensor Potentiometer Question
 

Hi guys- just a few questions - M103 engine -

Should an air flow sensor test be performed on a cold or warm engine?

For starters, I performed this test on a cold engine, and I got the following results: when I measure resistance between pins 1 and 2, I show a reading of 1.02 ohm. Do I have a bad potentiometer? Or is this reading due to testing on a cold engine?

I've been told that the reading should be closer to 3.6 to 4.4. But again, I don't know if this is on a warm or cold engine or if it makes no difference at all. Thanks!

http://ww2.justanswer.com/uploads/eu...r_flow_pot.PNG

Temp shouldn't matter for the resistance of the potentiometer, however I feel that your test values are wrong.

Did you disconnect the cable that goes away to the ECU?

Yes, I disconnected the cable.

On a side note- if I manually press down on the air flow sensor plate, the value on my multimeter rises (drops when I release), so at least I know that part of the potentiometer is working. But as far as the reading of 1.02, does that indicate a bad potentiometer?

Try this test procedure


Potentiometer adjustment;

3200 to 4800 ohms of resistance between terminals 2 and 3 when the airflow sensor is at rest.

560 to 1060 ohms of resistance from terminals 1 and 2.

The reading should increase to 3760 to 5640 ohms when the plate is at its lowest point.Adjust until this is achieved.

Goodness, now I'm really confused. What's the difference between our tests? I pulled mine right from the manual. On pins 1 and 2, I should get a reading of 3.4k - 4.4K Ohm.

Just to reiterate, when I performed the test I got 1.02K Ohm. So the test pretty much failed.

What's the range?

Readings between pins with flapper up and reading with flapper pushed all the way down.

I'm not sure what the range is. I'll test it when time allows. Do you know what the range needs to be?

I guess it's possible to calibrate these potentiometers. I'm basing that on Ivanerrol's comment about making adjustments. Work has stalled until I can get the special required to loosen the bolts on the pot.

I've just received a brand new Potentiometer.
I'll put in on later on today and give you some readings.

Hmmmmm....readings seem to contradict instructions I was given and posted:confused:

Heres some readings
1-2
http://farm6.static.flickr.com/5184/...a8723276_b.jpg
2-3
http://farm6.static.flickr.com/5181/...4228d540_b.jpg

1-3
http://farm6.static.flickr.com/5107/...48bac3b0_b.jpg

here's an old pot next to a new one - notice the wear marks and "flat" spots on the older one

http://farm6.static.flickr.com/5069/...e1f5b1d5_b.jpg

Ivanerrol, don't want to complicate the discussion, but I'm not seeing the tests for the results you're showing in the FSM. Test step 9.0 @ page 07.3.1122-121/115 indicates neg (-) probe on pin 1 pos (+) probe on pin 3 should read in the range 3.6kOhms - 4.4 kOhms (KOEO). I don't find any tests for (-) on pin 3 (+) on pin 1 or (-) on pin 3 (+) on pin 2. What do those tests indicate?

Tests between pins 1 and 3 on the example above reads 4350 ohms
within spec of what you have posted i.e. 3.6 - 4.4Kohms.
This is a static resistance test with an ohm meter on the unit with no voltage applied - so polarity is irrespective
(last image in the post above)

Oh yes, I see. Electricity is not my strong suit--business administration guy. Thanks for the explanation.

Higher planes, I think some of the confusion is in how the numbers are given. For instance 4.20K is the same as 4200. K means multiply by 1000. Does that help?
Paul