Pics ~ Exposed Optical Sensor Filter Harness 12553327

[buddy]

polarized capacitors have stripes too. If you just have an ohm meter and check the ohms across the line and resistance climbs for a while then its a capacitor.

Diodes are typically used for voltage regulation. The PCM regulates this voltage to 5VDC. Capacitors are used as close to an IC as possible on a power source to clean it up.

I believe it is there to provide as clean of a reference as possible for the high resolution timing source within the Optical Sensor. A small variation in the reference voltage would offset the feedback to the PCM.

Although if it were a diode you would only get an ohm readiing through it one way. And could be used to shunt voltage spikes to protect the PCM as JiFaire says. A diode alone is not a good way to protect a circuit, but maybe there are some tiny resistors on there too?

 

[dazed]

Okay I checked it with my ohm meter on the 2000k (highest) scale here are my findings...

My Digital display climbs up until it hits the 2000k

At any point I stop.... lets say 600 on the meter...and then i go back and resume It starts at the number I left off at.

If I short the pins out it restarts at 0 again.

I can even reverse polarity on the meter (switch leads around) and it will then count back to zero and continue counting up.


So it appears its holding a charge like a battery...acts like a capacitor as far as I can tell.

There is that other small chip (stamped IRO) and it appears to be in series on the Grey wire before the other chip on the way to the OS....so my guess is that some kind of resistor. I measure 1.0 on the 200 (lowest setting) scale of that IRO chip.

 

[dazed]

Okay got to thinking....maybe thats not stamped IRO but 1RO (one RO)...makes sense only 1 ohm resistance.

Or is that 1 Resistance Ohm....I dont know.

 

[buddy]

Thats a capacitor then, and the resistor is to smooth out its charge and discharge rates.

 

[JiFaire]

Yep, buddy's on it. It appears to be a clipping gate setup. Not a great one, either...

 

[JMJNet]

So what is a better DIY solution?

 

[buddy]

Instead of buying that new harness could wire in a single 4.7 uF Multi-Layer Ceramic Capacitor that is rated to 125C.

http://mouser.com/ProductDetail/Kem...=sGAEpiMZZMuAYrNc52CMZG3VgYp6UHXc6APHHSPl3Rk=


Or since the smaller ones are cheap throw on a couple more like 0.01uF and 0.1uF, with each capacitor in parallel
http://mouser.com/ProductDetail/Kem...GAEpiMZZMuAYrNc52CMZKgV%2bAI0ikNBqLfAZD2ZEhU=

These would go between the power and ground.

That resistor in there will slow the capacitors charge rate (current draw) and also provide some protection should the capacitor fail shorted, which is probably what happens when these things start causing problems.

Dazed are the resistor traces connected between the white ground wire and the capacitor?

 

[dazed]

So what is a better DIY solution?

Yes....that seems to be the million dollar question...oh heck, $85 Plus shipping from a vendor.:biggrin:

It would be nice to have a Homemade, or DIY solution on these forums..... I haven't seen it anywhere else, OTHER THAN what most people seem to get away with ....just removing it.

But when your throwing codes its hard to justify spending that kind of money and find out that wasn't the problem... Heck maybe a vendor could even make a parts kit, or fabricate there own.

It would be nice to have a valid test to know if its bad or not working. I'm not that electronics savy....maybe Buddy or JiFaire or anybody else for that matter could steer us in the right direction.

I also Like JiFaire mention of the quality "Not a great one" ....maybe there is room for improvement. :thumbsup:

 

[dazed]

Aw heck...I type to slow.... Buddy beat me to the post (already comming up with a fix)...

The resistor or 1RO is on the A terminal ( I believe it was Grey at one time).

No continuity to the D or white wire....just in series on that Grey wire then capacitor, then off to OS

 

[buddy]

Thats something Id need to see a close up of the wire traces, because it wouldnt make sense that there would be a resistor in line on the grey/power wire that goes to OS pin A.

Then by removing it we would be removing a resistance and affecting the reference voltage seen at the OS.

Can you measure from pin to pin on each of those harnesses and post the results
grey wire (A to A?):
white wire (D to D?):

I would expect each to have direct continuity and the capacitor/resistor circuit runs across them in parallel with the OS, so that it doesnt actually affect the voltage that the OS gets.

 

[dazed]

I can email you some better higher quality pics or you can click on my attachment in the 1st post
(the side with the 25 mark on the capacitor goes straight up and down with one end of the capacitor laying on it).

....So were on the same page, my response i was just talking about the resistor..being in series ...the capacitor does run in parallel on the grey (A) and white (D)

on a 200 ohm scale is Plug end A to A is 1.0 .... D to D plug end is 0.0

But I don't know if this filter is in "good working order" (minus the rubber)
Otherwise if someone has a new one (or an old one for reference) now that we know which termianls to measure across.

 

[buddy]

I guess the OS is high enough resistance that 1 ohm doesnt impact it much. Such as if OS is 100 ohms then current draw through the resistor would only drop voltage by .05V. The wires between the PCM and OS can easily add up to 1 ohm of resistance.

 

[dazed]

Here are some more close-ups CLICK TO ENLARGE




and those VEGTABLE PLANTS are Bhut Jolokia, Trinidad Scorpion, and Chocolate Bhut Jolokia in the background IN CASE YOUR WONDERING!

The Hottest Peppers in the world....

.

 

[jrsavoie]

Dang, I wanted to read a happy ending.

Did anybody ever come up with an aftermarket harness?

If not I'm going to buy one. The clip that holds the plug on the 94 is broke off and it's zip tied

 

[ak diesel driver]

there's been one on ebay for awhile

 

[ak diesel driver]

just looked I guess it's gone

 

[jrsavoie]

Dangf. I just looked a short while ago and didn't see one. Your first post got me all excited. hummerpartsonline has one for 69.95 shipped

 

[wiggle]

Hate to chirp in here now but if this was used to save the computer why wouldn't you just install a 1 ohm 10 watt resistor on the white wire [ground]....they are a little bulky 2 inches,plus wire ends

 

[jrsavoie]

As far as I know an optic sensor filter harness is not necessary on any vehicle. I've been taking them off and pitching them.

Have I been doing wrong?

 

[THEFERMANATOR]

As far as I know an optic sensor filter harness is not necessary on any vehicle. I've been taking them off and pitching them.

Have I been doing wrong?

The origanal purpose of the optic filter harness from what I found in some old GM bulletins was to surpress AM radio interference from the pump. This was why it was done away with in 96 or so as it wasn't really needed.