The trans has a trans solenoid on the passenger side and if you go to like pep boys and have the free test the code will read PO305 which means solenoid is low voltage. This sensor runs the odometer and regulates the automatic transmission shifting by speed from this solenoid which is cheap and easy to install yourself. You can visually see this on the passenger side rear of trans near the universal and is a electrical plug with a single wire installed with one ten millimeter bolt holding this sensor in the trans. This operates your shifting and when defective or goes bad it will not shift like in third or fourth gear even when you tryy manually, however your odometer will not work either. This part at the dealer cost like $35.00 and easy to install. Our vehicle is a courier and has 416,000.00 and just rebuilt the engine and trans for the first time. The bottom engine held up very well. Being from California secret is use like we do 30 weight castrol no multi weight oil, also being no external electric fan we installed one and helps keep the engine much cooler. Also important to change oil regularly between 3000 and 5000, also VERY IMPORTANT EVERY 80,000 replace water pump and timing chains.