Two problems related to automatic transmission control module have been reported for the 2002 Mitsubishi Diamante. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2002 Mitsubishi Diamante based on all problems reported for the 2002 Diamante.
Heater core defective and leaked coolant underdash on to transmission ecm and neutral safety switch. Because of this very common manufacture defect I had to have my heater core, transmission ecm, neutral safety switch replace. And my transmission rebuild, none of which were warranted by the manufacture and were not cheap.
January 12, 2005 one cold morning I noticed that the reverse gear did not go in as fast as it should it took like 1 minute to go into gear, when cold it would jolt before advancing in drive. Took it to the dealer, they did not find anything, so I picked up that same afternoon, next morning same problem. I took the car back on Jan 19, left it over night and they found it took a couple of minutes to go into gear, therefore, they decided to look at the transmission, the car has been at the dealer since 1/20 thru 2/7, after several discussions they have told me it is the heating core dripping on top of the computer damaging the sensors, today 2/8 the car would not go into gear at all. I have had grease with the seat belts, they had to be changed at 3600 miles, the tires (eagle) had to be replaced at 18,000mies, the brakes starting acting up at 6000 miles, the steering started vibrating at 12,000 miles. Bottom line this car is a mess, sucks and Mitsubishi does not want to be responsible for any of those problems, this is a big lemon!.