Everyone knows the stress of seeing the service light flashing on the dashboard of a vehicle. Most mechanics charge to retrieve the service codes. However, if you have a 1990 Toyota pickup, you can check the codes yourself without using a scanning tool.
Find the diagnostic connector under the hood of the Toyota pickup. Depending on the model, it is in the fender or under the dashboard on the passenger side. Refer to the owner's manual for your specific pickup.
Connect terminals TE1 and E1 with a jumper wire. A jumper wire is an insulated piece of wire used to make an electrical connection. You can find jumper wires at any electronics store.
Start the engine. The "check engine" light will begin to flash a pattern. The first set of flashes indicates the first number of the code. After a short pause, the second set of flashes is the second number in the code. For instance, for code 21, the light will flash two times, pause, then flash one time, dictating a problem with the Toyota pickup's oxygen sensor.
Turn off the engine, and remove the jumper wire.
