If you have a 1990 to 1995 Toyota and the Check Engine light comes on, you don't need to take it to a mechanic to check the trouble code. Mechanics usually charge a fee just to diagnose the problem. Going in with the code can save you money. Retrieve the trouble code yourself for your 1990 Toyota without using a scan tool.
Locate the diagnostic connectors. Usually they are located in the fender in the engine compartment. If they are not there, look by the kick panel on the passenger side under the dash. Check the engine diagram in your owners manual, if necessary.
Remove the rubber cover from one of the two diagnostic connectors.
Attach a jumper wire between the TE1 terminal and the E1 terminal. If you have a Tercel or an MR2, the jumper wire should be attached between the T and the E1 terminal.
Turn the key in the ignition and the Check Engine light will start flashing. These flashes indicate the code by flashing in patterns. For example, for code 31 the light will flash three times, pause, and then flash one time. If the Check Engine light continuously flashes two times every second, there are no codes.
Turn off your vehicle and remove the jumper wire.
