'burning' EGR question

[tblume]

Tyler has a temp probe. His isn't in the '95-'97 location, but in the EGR Valve spot (same as yours).

So that cap that fits into the EGR temp sensor plug....does that just connect one side to the other? Basically making it an open circuit?

yes and no: look at the first picture, that is the plug/jumper- creates a closed circuit.

and WHAT!? here I thought Ty had no temp sensor due to the boss being untapped. I may have a real bastid of a truck here; as close to a 3FE as you can get with OHC's and an extra .5L

 

[Ebag333]

yes and no: look at the first picture, that is the plug/jumper- creates a closed circuit.

Are you sure it actually connects the two? Or is it simply a cap to close it off and keep it clean?

and WHAT!? here I thought Ty had no temp sensor due to the boss being untapped. I may have a real bastid of a truck here; as close to a 3FE as you can get with OHC's and an extra .5L

Yes and no.

From your FSM pic, and the pic of your truck, it's looking to me like the OBD-I trucks have the temp sensor probe mounted in the EGR Valve housing (right next to the EGR pipe itself).

The OBD-I trucks have the temp sensor mounted on the opposite side of the EGR valve, meaning it's measuring temps a bit further down the line (and theoretically cooler).

Since Tyler's truck is OBD-I, I'm guessing that he has his temp sensor mounted where yours used to be, where you have that bolt in pic #2 plugging up the hole.

I'd have to look at his truck to confirm, but it would make sense.

I don't think your truck is any more of a "bastid" than anyone elses, though we do know that '93 (and even '94) had some weird things going on as Mr. T pieced together slightly different setups (disk vs drum, full vs semi floating, etc).

 

[tblume]

Are you sure it actually connects the two? Or is it simply a cap to close it off and keep it clean?

Yup, the pins in the cap are basically legs off a common bus; short circuit for the temp logic, it reads 0.2 ohm.

so from GotMud (and the FSM)
Quote:
122 (F) - 64K -97K Ohms
212 (F) - 11K - 16K Ohms
302 (F) - 2K - 4K Ohms

I have to assume this is a default setting or something for my (early obd1, non CA) ECU; interpolating the above numbers I can only guess at the temp value (1000*F?? if it even follows a trend) This gets pretty close to calculus for me, so I fear it

I assume that this same plug in a later OBD 1 or OBD 2 truck would throw a 71 or 402 code in a hot second.

 

[retrofive]

Yep Ebag is correct. I do have the EGR Gas Temp on mine shown in pic post #17

 

[Ebag333]

Yup, the pins in the cap are basically legs off a common bus; short circuit for the temp logic, it reads 0.2 ohm.

so from GotMud (and the FSM)
Quote:
122 (F) - 64K -97K Ohms
212 (F) - 11K - 16K Ohms
302 (F) - 2K - 4K Ohms

I have to assume this is a default setting or something for my (early obd1, non CA) ECU; interpolating the above numbers I can only guess at the temp value (1000*F?? if it even follows a trend) This gets pretty close to calculus for me, so I fear it

0.2 Ohm is basically nothing. You're measuring the resistance of the wire, that's it. Those numbers are Kilo Ohms, meaning 1,000 Ohms. So .2 doesn't even compare, there's no temp measurement for that (except maybe surface of the sun? )

That's very interesting, however.

I assume that this same plug in a later OBD 1 or OBD 2 truck would throw a 71 or 402 code in a hot second.

For OBD-I, I don't think so. That looks like an OEM cap designed to show a constant open loop, something I'm guessing tells the ECU to ignore that input. I'm betting Tyler could swipe it and use it, and it'd work perfectly.

I'm not sure of OBD-II. That I'll have to test....


Hmm, I suppose it's too much to ask for a part number on that.

 

[tblume]

I'm not sure of OBD-II. That I'll have to test....

 

[Ramblin Wreck LX450]

I've been following your conversation and have found it to be very informative. I'm heading to Radio Shack this weekend to by-pass the darn temp. sensor on my LX450. Thanks again. -Josh