1991 lexus problems i may be able to help, been inside and out of mine

can you post engine code please to be able to help you further..... computer (ecu) you don't need a new one that is for sure. you can buy a cheap code reader for vauxhall's (opel) OBD2 can read ecu codes. most problems occur in the egr most times it just needs a clean out. and some times it can be the CAT sensor plug. also the traction wires are under the car. so would check that. you can also buy a code reader/ writer that will test everything. I have one for mine and it has saved me a lot off money. and can read any ob2 plug. and other makes off cars. handy to have. save you a lot of money at a garage. but with engine code that will help more at the moment.

1. To reset MAINT reminder light after engine oil replacement, turn ignition switch to OFF position with odometer reading showing. Turn ignition switch to ON position while holding down trip meter RESET button.
2. Hold trip meter RESET button down for at least 5 seconds. Odometer should indicate "000000" and MAINT reminder light goes out.

THE REQ MAINT LIGHT COMES ON TO TELL YOU THE CAR IS DUE ITS NEXT SERVICE within 800 miles.

disconnect the battery for about 30 secs. this will clear out the ECM (computer) and will reset that light for you.

I do not have manual in front of me but it is in the owners manual. best I recall is (mine is 2006 rav4) to put trip meter on A with key on, turn key off then push and hold trip meter button down while turning key on.....or something like that ....read manual.....