Volvo: Volvo 1996, 850 wagon, wont start, volvo 850 wagon, reverse light switch

Question
QUESTION: I have an 1996 Volvo 850 wagon that won't start.  It has a new battery but will not crank.  I can jump start the car and drive it but when I shut it off, it will not crank.  All fuses in fuse box under the hood are good. I have tried to jiggle the shifter, nothing. I have tried to jiggle the key, nothing.
Thank you for your time.

ANSWER: Richard,
Make sure that the car is in Park. Read the fault codes in the trans to see if the Gear position sensor is bad. There is also the chance that the ignition switch has failed. The Gear position sensor has a high failure rate. It acts as the neutral safety switch the reverse light switch and the gear position switch.

---------- FOLLOW-UP ----------

QUESTION: Thank you for your fast response.  You say, "read the fault codes in the trans".  I don't know where they are or how to read them. Also, where is the Gear Position Sensor?  I would like to fix this myself so any detail information is appraciated.

Answer
Richard,
You need a scan tool hooked to the OBD II connector. Since you do not have a scn tool it maybe time to take it to a Volvo shop that has the proper scan tools. If you use a generic scan tool you get generic codes and they are not as specific as the factory codes. The gear position sensor is on top of the trans, where the shift cable attaches.