Looking to buy a chrysler grand voyager 3.3l auto limited top spec the year of the car is 2001 with these problems p0731 and p0500 and just wondered how serious they are and what the cost would be to fix this problem

2005 plymouth voyager ??? Didn't make plymouth vehicles that year . Plymouth Voyager/Grand Voyager Overview Manufacturer Chrysler Corporation (1974-1998)
DaimlerChrysler (1998-2000) Also called Chrysler Voyager/Grand Voyager (Mexico; USA for 2000 only) Production Body and chassis Class Minivan (1984-2000)
Full-size van (1974-1983) Chronology Successor Chrysler/Lancia Voyager (USA, 2001-2003, Mexico SWB until 2007)

P0500 - Speed sensor circuit problem.
P0700 - Transmission Control System Malfunction
P0731 - Incorrect 1st Gear Ratio

Did you forget to reconnect something on your transmission? Check your electrical cables.

its mounted to top of fuel tank , I just looked it up at auto zone library ,you can too ,it gives directions ,just go to AZ site log in and list your vehicle, and go to repair help then to fuel system. its all free and no spam . good luck.
Woody

check youir transmission fluid levels and maybe change the fluid.

check for codes in abs

DTC P0500 - Vehicle Speed Sensor Malfunction
This fault code mean that the vehicle's speed as read by the Vehicle Speed Sensor (VSS) is not working properly. A code P0500 may mean that one or more of the following has happened:
The Vehicle Speed Sensor (VSS) is not reading (functioning) properly
There is a broken/frayed wire leading to the vehicle speed sensor
The vehicle's PCM is not correctly configured for the actual tire size on the vehicle

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try here ->http://motors.shop.ebay.com/__?_from=R40&_trksid=p3841.m39.l1313&_nkw=voyager%20owners%20manual&_sacat=&rvr_id=220625671658&MT_ID=335&crlp=3167763268_9887&tt_encode=raw&geo_id=491&keyword=voyager+owners+manual&adgroup_id=1215496138

P0700------- Transmission control system malfunction. 10 to 1 the control unit needs replacing.

I replaced the speed sensor & this took care of the problem.

Probably The Dealer But Napa Should Have Them As Well.