Ferocity02

iTrader: (60)

Quick question, the park/neutral position switch appears to tell the PCM what gear the transmission is in (according to the wiring diagram). Does the PCM alter the tune or anything else depending on which gear the transmission is in? I read somewhere that it will adjust the idle differently. Is this true, does it do anything else?

The reason I ask is because I'm putting a T56 into my '01 Silverado. I grounded two of the wires on the transmission range switch/sensor so it displays DRIVE when the engine is off. Then for some reason when the engine is running it will display 2ND, which I think is default. It will display 2ND if I don't ground any of the wires on the range switch too. How can I wire the transmission range switch to display DRIVE all the time? Or does it not even matter?

Thanks!

jgb989989

Shouldn't matter. Neutral safety switch is so it doesn't start in gear. Prndl switch tells PCM to expect load and something with the tcm.

slow67

iTrader: (2)

If you ground the PNP switch, the computer changes tables from the in gear to the park/neutral tables for idle.
As far as which gear, are you referring to the dash display or the one in the scanner?

Ferocity02

iTrader: (60)

The transmission range switch has four wires; black/white, yellow, gray, and white. I used this post to determine which ones to ground. Mine were different I think because mine is a truck, but I grounded two at a time until I got it to display DRIVE with the engine off. Once running however, it will display 2ND. By display I mean on the dash, I don't have tuning software. Will the display show differently that what the PCM sees? I was assuming they would be the same.

I have the clutch switch hooked to the yellow neutral safety switch wire and the purple/white starter relay supply voltage wire from the PNP switch. It works perfectly.

Once I start the engine, the idle drops down to what it would normally be if the truck was in gear with the auto. It drops down about 1/2 second after starting.