A modern vehicle's on-board diagnostic (OBD) computer monitors engine sensors and activates a warning light when a problem is detected. For Toyotas manufactured after 1995, you can scan the computer for a five-character trouble code. Toyotas built before 1996 use two-digit "blink codes" instead.
To read the error code on a pre-1996 Toyota engine, you must jump two wires in the diagnostic terminal. The on-board computer will respond by flashing the check engine light in a pattern of long and short dashes, called a blink code.
Some error codes on Toyotas are comprised of two-digit numbers such as "25." The blink code consists of long flashes for the first digit and short flashes for the second. For example, "Code 25" is represented by two long flashes followed by five short flashes.
Code 25 on a Toyota indicates that the air-fuel ratio is lean (too much air). This error condition is often caused by a faulty O2 sensor, a vacuum leak or a problem with the fuel pump. Refer to your owner's manual for specific diagnostic information.
