I have a 2003 a4 quattro 1.8T automatic with a TRIANGLE warning light. The are NO OBD2 CODES. The PRND lights are normal and not on or flashing, but car barely moves forward at all... or not at all. Reverse works. I have been told to consider LIMP mode and that replacing the TCM (Trans ECU?) might resolve. I happen to have the same car in a 2000 model year as a parts car, so I have an extra ECU. I want to switch the and check tranny fluid level (I noticed fresh tranny fluid on the ground after I started the car after sitting for several months). Yes, checking fluid level is best to do first, but the car is in the street and checking/changing trans fluid is difficult.... must be done from underneath with car elevated. I have determined the trans type are the same or similar.

From the discussion, it sounds like ECU on my 2000 in under carpet, while it is located in engine compartment on my 2003.

anyone have comments on my situation? what does just the TRIANGLE warning light mean? Can I switch ECU's?