2001 Town and Country issue

I have an issue with my minivan where the speedometer needle jumps from a maintained speed to zero and then back to the maintained speed. It happens without notice and you dont notice anything change in velocity. Some times it will actually go all the way around and be pegged on the backside of the stop pin…meaning going 150 mph, and stay that way for a day or two until something releases it. Also, the tachometer jumps about 300 rpm intermittently while you are crusing, when there is no real demand on the engine to accelerate. This makes the cruise control annoying as it reacts to the tachometer changes. It has been to the dealer multiple times and they cant figure out what is going on…think it may be a ground issue or related to the transmission in some way. Any ideas? Do you think the issues are connected?

The speedometer problem may be due to a bad connection to the gauge or the gauge. If I remember correctly I think the gauge is tied to the BCM module and if so the trouble may be within it but hopefully not.

The engine surge may be due to a bad plug wire connection, faulty plug, or something else concerning the ignition system. My money would be on something with those things. The throttle position sensor may also be a problem and I suppose even a bad ground connection in that area may be the cause. I would first monitor the throttle sensor to see if that is making the changes.

The car has now been to two different dealers, with similar diagnosis. Either wire harness, PCM or TCM. The second dealer has indicated they are not able to access all signals successfully, and I will need to replace the wireharness. They claim that the harness is fused into one hard, “solid” mess from engine/transmission heat. Over $2.5K to replace with no guarranty to fix the issue.