"Lost"Function from trip button
 

Hi! Does anyone know how to re-establish lost "Engineers"test function off trip-switch on 2.1 V6 53/03 model?

xtype62, lets start with proving what works and what doesn't so we have an idea of where the problem may lie. First things first, if you hit the TRIP button, does the display change on the instrument cluster to show you the tripometer, mileage, and MPG/LPM? If yes, then we know the turn signal stalk is good. If not, then your problem as to why you can't access the engineering test mode is that.

Next, what happens when you depress and hold the TRIP button and while the TRIP button is depressed you start the car, continuing to hold the TRIP button down for an additional 5 seconds? Did you see the "ENGINEERING TEST" (or something to that effect) show up in the instrument cluster display after about 3 seconds of the engine running? If you do see "Engineering test", then you should immediately release the TRIP button to keep the instrument cluster in the diagnostic mode. If you hold the TRIP button too long, it will kick the instrument cluster out of the diagnostic mode.

If you are not able to enter the diagnostic, then your problem most likely lies with the ECU/instrument cluster itself. Unfortunately, this is going to require a dealership level computer to get into that and make any needed changes.