If you are experiencing issues with faulty shift indicator on your instrument cluster it is most likely your mode selector switch. This may be indicated by shifting to drive but displays neutral, reverse showing while in neutral, flickering or jumping, or no light at all. Because the transmission is electronically controlled this condition may also come with erratic and violent up and down shifting due to negative feedback through the TCU. This condition is often intermittent. A replacement part can go for upwards of $250 and many of you have indicated that the replacement part may not work either. Their is a simple fix. Took me 30 minutes and I'm no mechanic.
1.) Locate the mode selector switch on the driver side underneath the vehicle attached to the transmission. You should barely see the green serial number tag on the transmission body above it. You will also see a wire cluster connecting to the part from the rear of the vehicle to this part. This part is roughly the size of your palm.
2.) Once located pop off the dust cover with a screwdriver which is connected with spring steel in three points. Releasing the bottom and forward will allow removal without having to get to the difficult top point. Then remove the 14mm bolt attaching shift linkage to switch and pull away.
3.) The part is attached with two 10m bolts. One on forward and one on top slightly recessed from the body of the switch. You can get to this with a 2 inch extension and socket wrench, a little patience, and a flexible wrist.
* Make sure the vehicle has cooled down as you will touch the exhaust pipe and transmission body.
4.) The unit will come loose from the transmission, however is still attached via cable cluster. About six inches up the wire is a molex connection. This plug is attached to a metal plate and I had to break the plastic attachment to loose it so you'll have to figure that one out! You'll also have to clip some wire ties as well. The plug can now be separated by popping loose one plastic pressure tab and carefully pulling.
5.) With the unit in hand remove the cover screws with a torque bit t-15.
6.) Pay attention to the red gasket seal as it easily expands or contracts with temperature differences making it impossible to fit upon assembly. Pressurized carb cleaner caused mine to expand causing me to cut it down to fit. I'm sure this will shrink with heat causing a gap in the seal possibly exposing it to water.
7.) With the seal removed use the carb cleaner to remove old debris and grease from the cover, contact tracks and traces, and contact pickups. If their are signs of broken or severely worn tracks or traces then the part will need to be replaced. Mine was fine at 118K mi.
* Pay attention to the spring metal contacts as they may need a little bend back and work the springs on the arm contacts to ensure they will hold contact to the track.
8.) Apply new lithium white grease to the contacts and work the unit back and forth manually.
9.) Reassemble, reinstall, and if you broke the plastic tab to hold the body of the molex connector to tranny then improvise with new wire ties.
* Don't forget to reattach linkage.
10.) Turn key and test. The shift indicator lights should change seemlessly without flicker or jump to the desired gear. With the proper signal being sent to thru the computer to the tranny, shifts should be smooth.
*Note you may uncover additional problems in the transmission at this point that may have been preexisting or due to a result in continual wear from hard shifts relating to sustained fault in the mode selector switch. I've noticed that their is no longer an issue with down shifting however have discovered that my valve body, fluid pressure, or shift solenoid is causing violent shifting between 1-2 which wasn't eliminated with this fix since it had already been present. In either case I won't have to purchase a mode selector switch saving me $250:
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