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Optic sensor filter

matuva

matuva

Tropical 6.5er
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Location
New Caledonia. An island in south west pacific, cl
Hi all,

couldn't find a thread talking about : is the RF filter in the IP harness on 1995 trucks absolutely necessary ?

What happens if we get rid of it and don't put it back when swapping the IP ?

I know this is a souce of trouble, but I don't know if I must put it back or can bypass it :confused:
 
Matuva, the truck will run fine without the filter, but if you get a miss-fire or bucking after you remove it that might be because of the missing filter.
 
I have never seen one on mine, must have been removed in an IP replacement from original owner.

Is this IP for the truck in the "Another no start" thread, did you do something to diagnose it as a bad IP?
 
No that's from another truck.

The guy was told by a mechanic it's a bad IP.

The guy bought a brand new IP and so he decided to put it on the truck.

The one from the "another no start thread" is still on the side of the road, no spare PMD yet to test
 
IIRC, if you put a new IP and new harness, the newer harness may not need the OS harness. It was a discussion here when the forum just got started.
 
How do you eliminate the OS harness? Do you cut the box out and splice the wires?

Is this the same harness I replaced to eliminate the fishbite in my 95 Tahoe?
 
JMJNet said:
IIRC, if you put a new IP and new harness, the newer harness may not need the OS harness. It was a discussion here when the forum just got started.
Click to expand...

Too late, before I told him, the mechanic install the new IP, with the RF filter.
Works fine though, but I would have rather like this filter out...

jrsavoie said:
How do you eliminate the OS harness? Do you cut the box out and splice the wires?

Is this the same harness I replaced to eliminate the fishbite in my 95 Tahoe?
Click to expand...

just unplug the filter, throw it out, and reconnect the harness to the OS.
 
jrsavoie, the RF harness was built-in to all OBD-I trucks (1994 and 1995. It functions as an RF choke, protecting the PCM and the OS electronics from voltage spikes induced from other sources. As Dennis commented above, in most cases, it can be removed and the truck runs fine - in others, the truck can start to run rough and misfire a bit, indicating that there is some transient RF there that needs to be clamped. Personally, I think it should be replaced in OBD-I trucks (to protect the PCM) - not eliminated, but that's up to the owner... $50 is $50.

Starting in 1996, with OBD-II PCMs, the RF filter function was built in to the PCM... but for some reason, some trucks still come with the RF filter. It should make no difference - redundancy in filtering should not hurt anything - but when the filter goes bad, it still causes fishbite.

The filter can be safely removed in OBD-II trucks with no worries about damage to the PCM, and does not need to be replaced.
 
Yea, I am not sure if it is needed. I have just been doing alot of reading and I think I did read that. I think I read that if you are having fishbite that it could be caused by a bad filter. I also think I read that it is a Radio Noise Eliminator?
 
It is a simple power filter, with a single capacitor to filter it. It is a good practice, but proven unnecessary on many vehicles. A bad one surely can cause problems, but that doesnt mean you need one at all. If you dont have one and you do have problems, then you may be getting EMI on the lines and it could help.
 
Buddy, that is how I understand it also. If you don't have one that is fine. If you are experiencing fishbite then one might want to put one on. Or if you have one installed and experience fishbiting you might want to take it off to see if the fish bite goes away. For the most part they are only found mostly on 94 and 95 6.5's. I have done so much reading the last few days my brain might need a filter.
 
Just my thoughts on what I plan on doing with my 95 6.5 is I plan on leaving my filter in place and if I have problems I am just going to take it out and see if the problems leaves with the filter. That's just me though. Others have their own opinions on the filter and that is good.
 
Sounds good Matuva. I am having touble with my truck stumbling and running rough. Code 18 keeps comming up which looks like I might have a optic sensor going bad. So I took out my filter in hopes it would run better. But it didn't help so I am going to put it back in. But like you, if it starts to run bad or fish bites I am taking it out. Good luck.
 
Just a quick shot for those, like me, who work better with pictures.

If it is supposed to protect the PCM on the ODI trucks, I'd leave it be. Mine's a 96 so...outa there.
 

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