P1870 Transmission code
 

1996 Chevrolet Corsica 3.1, 200, 000 miles Motor in good shape, uses no oil between oil changes at 6,000 miles. Got a P1870 Transmission code: trans component slipping. Thoughts about what the problem is? Trans fluid and filter changed about a year ago, added some Lucas transmission conditioner couple months ago. Trans shifts great and does not leak. This is my sons car, He(we) can't afford to replace the car. Thanks