The Park and Neutral Position (also known as Range Position or Inhibitor ) switch is not functioning correctly and this would affect the transmission shifting. The transmission could go into Limp Mode and this means it would be locked in one gear and not upshift. This can damage the transmission.
Check the wireharness connector for damage and contaminations. Does wiggling the gear shift results in the light showing intermittently?
Images (Click to enlarge)
Tuesday, November 27th, 2012 AT 2:12 PM