Camry 2.2L Auto Transmission 'slip' & engine management light

I have a 1998 Camry 2.2 auto with approximately 80 000 miles (128 000km) and full service history. Recently I have been experiencing what I can describe only as transmission 'slip' that happens about 2 to 3 times a day and when this happens, the engine management icon lights up, but goes off a minute or so later. This is usually at low speed. The revs would climb beyond where it would usually change into the next gear, but keep climbing to about 3000 revs, the EM icon lights up then suddenly it would change into the next gear. About a minute or so later the icon goes off and it drives normally again. Sometimes when accelerating at low speed, the revs would suddenly jump to 3000revs, then drop back to normal. I have no idea what this can be, please help.