catalytic converter temp probe

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tjhaga

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I'm replacing a catalytic converter on a late model fj40. I assume the probe is a temperature probe and goes into the output side and connects to the wiring harness under the drivers seat.
My question is where is this info recorded? Is it part of the engine temp gauge?
 
tjhaga said:
I'm replacing a catalytic converter on a late model fj40. I assume the probe is a temperature probe and goes into the output side and connects to the wiring harness under the drivers seat.
My question is where is this info recorded? Is it part of the engine temp gauge?
Click to expand...

It is a temperature probe, and is used by the emissions computer. It has no feed to the temp gauge in the cluster. That probe is located on top of the head.
 
To put a finer point on this, it is part of the air injection system. If you don't have the probe the system stays in bypass mode. This is required for it to direct air into the exhaust.
 
LITP - No, this is purely a temperature probe, similar to the one from the carb cooling fan. When this one isn't connected or it gets very hot it creates an open circuit. This directs air from the smog pump back into the air cleaner, also known as "bypass" mode. The idea is that the catalyst in these things works great at high temps, so injecting air upstream of the cat will increase operating temps. Well they can also get too hot, this would cause them to melt or other unfortunate outcomes. If the probe senses too much heat it switches to bypass.

Capture.webp
 
Hi Guys, Can the temp sensor have an affect on emmissions?
I didn't pass my smog and I'm trying to uncover what could be the culprit.
 
Joe-
A little, modern cats should be more than fine without the extra air provided by the A/I system. Do you still have the OEM Cat or what? Where did you fail?
 
A new Cat would probably help then. They aren't too expensive, just put in a generic one, just make sure it has the tube for the temp sensor.
 
Joe-
I found an old thread of yours about emissions again. Did you ever go through the systems and check them all? Did you re-time it?
 
I did. I had to take it in to a shop and they replumbed my emissions, including replacing some emission related valves.
Since then, I even rebuild the heads. My timing is way off. When I took it in to get smogged yesterday, I was told I was 12 deg advanced. Not sure how that happenned.
I think I'm going to run a CAT cleaner and fix my timing first. If that doesn't work, I'll replace the CAT, since a drop-in unit is pricey.
 
1982FJoe40 said:
I did. I had to take it in to a shop and they replumbed my emissions, including replacing some emission related valves.
Since then, I even rebuild the heads. My timing is way off. When I took it in to get smogged yesterday, I was told I was 12 deg advanced. Not sure how that happenned.
I think I'm going to run a CAT cleaner and fix my timing first. If that doesn't work, I'll replace the CAT, since a drop-in unit is pricey.
Click to expand...

$121 from Rock Auto

I've never heard of a cat cleaner though, worth a shot.

Cat.webp
 
Well, I'm not sure, my whole exhaust system isn't stock, I bought one without flanges and had it welded in. The one I bought is identical to that and works well, I was able to pass smog pretty easily. You could always call them and see if they can give you a length and then measure vs the old one.
 
A 2F will fail smog if the air injection system isn't pumping air into the exhaust. There's plenty of treads in the 60s section (2F engine) where time after time the engine wouldn't pass until the air injection system was fixed.

As has been proven by another member, if the air pump outlet is directed straight into the exhaust pipe, down stream of the manifold, upstream of the cat of course, a big improvement in lowered emissions can be detected... Better than if the air injection system is hooked up in its stock configuration.
 
tjhaga said:
I'm replacing a catalytic converter on a late model fj40. I assume the probe is a temperature probe and goes into the output side and connects to the wiring harness under the drivers seat.
My question is where is this info recorded? Is it part of the engine temp gauge?
Click to expand...

To answer the OP: It's not 'recorded'. It's just sends a signal input (resistance valve depending on Temp of CAT) to the emissions box that controls, more or less, the 'on/off' condition of various valves in the emissions system. As stated, it functions is conjunction with the Air Injection system. Has nothing to do with engine temp.

The Emission FSM (in my sig as a pdf download) has good explanation of how most of this works.
 
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