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Discussion Starter #1
the y-body lt1 cars have an oil temp sensor..

having another temperature input for datalogging and fan turn-on that you could put anywhere would be pretty nice, wouldn't it...

i notice the bins for f-body ecms do have the constants for oil temp; and it spits out a constant -32 degrees.

does anyone happen to know if GM was nice enough to leave that pin functional on the f-body ecm?

does anyone happen to have a pcm pinout diagram for a y-body that would tell me which pin it is, so i can try grounding it and see if it responds?
 

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Oil temp sensor on the Y-Body feeds PCM pin D26. It's a resistor type of sensor one side to sensor ground and the other to pin D26. Probably no wire in the F-Body. It's a one byte field in the PCM log file, however the question would be " does the F-Body PCM software update and maintain the validity of that byte" It displays at -34* F on Datamaster so the byte of data in memory may be '00' . Theoretically if the F-Body code maintains integrity and updating of that byte, with a known signal and a Datamaster OR TunerPro RT hack it could be possible to log it. If it needs Y-Body code to maintain the byte the that's a big problem. Right now the line (D26) s/b floating at +5V (my guess) test would be to ground it and see if PCM displays high temp I believe it would be about 347*F as that's what the TunerPro .adx file is saying (-40 to 347 is the swing). Some good PCM knowledge over here, but it's geared to TunerPro RT GM EFI Systems
 

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Discussion Starter #3
i have a dead ecm apart on my desk, and that pin definitely is traced into the board, so it's not like they completely skipped the circuit for it on the f-body ecm.. that's a good start

whether it functions or not, i guess i'll find out when i'm at my car next
 

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steveo, I did some testing on my bench setup, 16188051 PCM running F-Body code. Put a test lead on PCM pin D26 (oil temp to PCM). Since it's an open line it floats at 5.0 volts on the scope. I was running TunerPro RT temp readings were -34F (-40C). Tied D26 to ground and TunerPro readings went to 325F (163C). Tried a 2.K ohm resistor on the line to ground and temp went to 68F (20C) voltage was 2.8 V on the scope . So this says the F-Body code is reading the input and updating the oil temp. Not sure if a linear WB output of 0-5V would read linear on the oil temp circuitry. But if you tied a 0V output sensor or circuit to that line it would read 325*F on the scanner program when it's active..
 

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Discussion Starter #5
yeah! and i confirmed it today too, not only that, when i grounded it my fans turned on.. so that confirms is utilitizing the oil temp constants (which are maxed out in f-body bins by default, so it ignores that sensor).

that's awesome we have an extra input

it's just a shame they dont have any fuel/spark relational tables for oil pressure, or we could do dual tuning with that pin as a switch.

at least it can be used for datalogging and fan turn-on.

wiring a simple grounding switch could be used for manual fan switching via the ecm too. might be cleaner than the usual splice. seems you could do fun things like make your manual fan switch automatically override at high rpms, if you do that.
 

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yeah! and i confirmed it today too, not only that, when i grounded it my fans turned on.. so that confirms is utilitizing the oil temp constants (which are maxed out in f-body bins by default, so it ignores that sensor).

that's awesome we have an extra input

it's just a shame they dont have any fuel/spark relational tables for oil pressure, or we could do dual tuning with that pin as a switch.

at least it can be used for datalogging and fan turn-on.

wiring a simple grounding switch could be used for manual fan switching via the ecm too. might be cleaner than the usual splice. seems you could do fun things like make your manual fan switch automatically override at high rpms, if you do that.
That's cool
Could it be used to log a wideband 02?
What other inputs are available that arn't used ?

Mitch
 

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Discussion Starter #7
i doubt you could easily hack it for a wideband. the sample rate is about the same as an o2, i think..but... you'd have to build a magic box to convert ac voltage to impedance though, and the ecm wouldn't do anything useful with it.

i'll start messing around with the mystery pins part now, there are lots of weirdo unused pins on the ecm that have electrical traces of some sort going to them..

first off i've found that there are some extra filtered sensor grounds, which might be useful for custom wiring, eliminating splices, or whatever..
 

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I was thinking more on the line of feeding something like the 0-5V LM2 Wideband controller output setting into the port, similar to Datamaster hack for the AC pressure port. But it looks like the oil temp also controls the fans and they will kick on at low voltage to that port.
 

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Should work.. is there a wire going to D26 that can be spliced into. Otherwise not to many people have PCM pins laying around, want to split apart the 'D' connector to add the circuit AND have tuning capability to set fans on using oil temp. In that case the current procedure http://shbox.com/1/fan_sw_diagram1.jpg would be more desirable. I'm more interested in a wideband controller in for real time logging w/o messing up my A/C. I need to scrounge up some sort of 0-5V power source like an old TBS or variable resistor and do some bench testing when I have time.
 
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