How to test 911/996 Automatic Transmission gear position switch?

[larry504@comcas]

My backup lights are not working along with backup video camera on my 2002 911/996 Carrera. I have checked fuse and lamps and they are OK. After reading through my Porsche Service Manual from Bentley Publishers it recommends to check the Automatic Transmission Gear position switch since it controls the backup lights. After looking through the schematics I cannot find out how to perform a test on the Gear Selector Switch before I purchase a new one (which runs anywhere from $250-$400) I would like to "test": the gear position switch to ensure that it is faulty before purchasing a new one. Any help form anyone concerning this issue would be appreciated.....

[DRACO A5OG]

Have you tried the 996 section?

On a car like a toyota the gear shifter selector is mounted on the transmission. The cable may have stretched just enough as not to hit the reverse switch. Try tightening the adjuster, there should be one for this specific purpose, take note how much you turned and turn in increments as not to over do it or you may not be able to get into gears. If not a top end adjuster, the adjust may need to be made at the selector itself via a nut attached to end of the cable.

I had to do this on my lexus on a trans rebuild.

Welcome aboard.

[tcar]

Originally Posted by DRACO A5OG

Have you tried the 996 section?

On a car like a toyota the gear shifter selector is mounted on the transmission.

...and Toyota was involved witht the 996 and 986 (Boxster) design, so...

[DRACO A5OG]

^^^ LOL, I think they designed the loverly IMS

[larry504@comcas]

After looking at the schematics it looks like the Gear selector switch feeds the Tiptronic Control Unit which connects to the Switch Lifting Tipronic circuitry that outputs a "back-up" light signal.
It seems that everything is controlled by Logic circuits and without the codes you are left with changing out expensive circuitry to find a "simple problem". Still digging....Thx

[Bob Kontak]

Originally Posted by larry504@comcas

After looking at the schematics it looks like the Gear selector switch feeds the Tiptronic Control Unit which connects to the Switch Lifting Tipronic circuitry that outputs a "back-up" light signal.
It seems that everything is controlled by Logic circuits and without the codes you are left with changing out expensive circuitry to find a "simple problem". Still digging....Thx

I hear you on the logic circuit but can a logic circuit be as simple as I am on or I am off?

Your hand or fingers do something that moves or signals something (switch?) upstream of the control unit.

Do you move a selector into reverse?

I have a 915 transmission which is like a tractor.

[larry504@comcas]

Hi Bob...Your right it should be quite simple, but this is complicated when they don't give you the information that you need. I have the schematic of the selector (from Bentley) that is on the transmission but it doesn't give you the information that is needed as to what pins are grounded when in the various P-N-R-D positions. Even if I go through and ohm it out I still won't know what the correct configuration should be. Hate to buy the switch and find out that it is NOT the problem.....so the search for knowledge continues....thanks for the response.