Cadillac Repair: 96 Eldorado, climate control, test procedures

Question
The old caddy has developed a problem with the tcc.(I think)It shifts smoothly from g 1-2 @2000rpm around 15 mph;shifts smoothly from g2-3 @2000rpm around 30mph. It will not shift from g3 at any speed. It used to shift at about 45 mph @ 2000rpm. Tt makes no difference if the trans is hot or cold.

Answer
Is or HAS the CHECK ENGINE light on the dash ever illuminated ?.

If it has you will need to access the computers via the climate control panel and perform some test procedures using the climate control panel.

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