: How does the PCM know what gear it's in?



eldorado1
05-18-04, 05:02 PM
I'm working on a little project, and I need to know how exactly the PCM knows what gear the shifter is in... I suspect it has something to do with the neutral start switch on the tranny itself, as it has 7 or so wires coming off of it... But - the service manual doesn't have a pinout or anything! At least that I can find... Can somebody tell me if the neutral safety/start swith is what I'm looking for here? And if so - what the pinout/connection sequence in gears 4,3,2, and 1 are? Thank you very much!

32V_DOHC
05-18-04, 06:02 PM
The PCM knows the gear selected by the gear selector switch on the trans. It also knows what gear it is in by the pressure manifold outputs.

John

eldorado1
05-18-04, 06:12 PM
The PCM knows the gear selected by the gear selector switch on the trans. It also knows what gear it is in by the pressure manifold outputs.

JohnThat's what it was called - the transmission range switch. The service manual I have shows the pinouts on the 4t60e switch, but not the 4t80e for some reason?? Does ANYBODY have this? I *desperately* need it! Thanks!!!

dloch
05-18-04, 06:40 PM
That's what it was called - the transmission range switch. The service manual I have shows the pinouts on the 4t60e switch, but not the 4t80e for some reason?? Does ANYBODY have this? I *desperately* need it! Thanks!!!
John is correcto...What year trans are you playing with?

eldorado1
05-18-04, 06:47 PM
John is correcto...What year trans are you playing with?I'm looking at a 94, but it should be the same from 93-2003(+?) If you have a service manual for any other year, could you please look for the tranny range switch?

dloch
05-18-04, 06:51 PM
I'm looking at a 94, but it should be the same from 93-2003(+?) If you have a service manual for any other year, could you please look for the tranny range switch?
I'll take a look when I get home tonight.

eldorado1
05-18-04, 06:57 PM
Thanks a bunch!

dloch
05-19-04, 10:24 AM
The manual doesn't have what is called a range switch..... There is a range reference chart..... it shows what is on and/or applied while the trans is going through the gears. It also has a pin out of the connector.

eldorado1
05-19-04, 12:06 PM
The manual doesn't have what is called a range switch..... There is a range reference chart..... it shows what is on and/or applied while the trans is going through the gears. It also has a pin out of the connector.If it shows what pins are connected in the various gears, that's what I'm looking for... like this, but for the 4t80e: (Oh, and this wasn't even listed in the index - I had to thumb through the diagrams for it)

dloch
05-19-04, 01:14 PM
I have some Tif files for you, where do want me to send them?

eldorado1
05-19-04, 01:16 PM
how about g_i_jim2000@yahoo.com? I think I've got 4megs of storage there..

dloch
05-19-04, 01:25 PM
Just sent them

eldorado1
05-19-04, 01:31 PM
Got it! Now I can get started on the electronics for my manual transmission controller... :bouncy:

eldorado1
05-19-04, 01:47 PM
Actually, I think I need one more thing - a pin out of the "C2" connector... I'm hoping it's a 7 pin connector like mine....

eldorado1
05-20-04, 12:52 PM
Bump to the top - seems as though these stupid Helms manuals only tell you 1/2 the story... Anybody have a year different from 94 and 97(I assume?)?

eldorado1
05-21-04, 03:59 PM
Brought my question to the local cadillac service shop... Their response: "uhh, I'm retarded." :rant2:

eldorado1
05-31-04, 10:00 PM
After conversing with a few different people, the general consensus seems to be that when the engine is running, the tranny oil completes circuits via the X,Y,Z pins, and tells the PCM what gear it's in via a form of binary. Is this one of those redundant systems, or is this the only method of checking the user-selected gear? It seems as though if you wanted the fastest shifts, you would have plain ol' electrical contacts? I'm really confused now :eek: