First, the 91 should not have the led on the TCU-did you notice a window on it when you replaced it, or can you double check to be sure.

If yours does not have the LED on the TCU:
Sounds like it might be a code six......which may or not store in the TCU, sorry about that.

The manual says that if the owner decribes this issue, drive the car until it happens again and check the codes WHILE the car is still on. This code points to the gear position switch or wires.

 

Where is the TCM located on a 1991 Honda Accord LX? I don't know where to look or what to look for. Can you help me anyone? tonyway90

 

Passenger side of the car under the carpet near the firewall. You have to pull back the carpet and remove the metal plate to get to the ECU and TCU.

 

I want to say I hVe a 91 ex exact sane problem! There was burned components in my TCU I think it was 43,47 then my cluster had bad spot that made s light go wacky! I triple hate the sports shift feature it's useless!!!!