The ECU contains a built in self-diagnosis system which is tied into the trouble code system that is incorporated into the engine signal network. The trouble codes are detected and are exposed by a "CHECK ENGINE" warning light on the instrument panel, which flashes code numbers 12, 13, 14, 21, 22, 23, 24, 25, 26, 27, 31, 32, 41, 42, 43, 51, 52, 53 and 71. The CHECK ENGINE light on the instrument panel informs the driver that a malfunction has been detected. The light goes out automatically when the malfunction has been cleared.
The 1984-87 Van used malfunction code numbers 1 through 11.
The diagnostic code can be read by the number of blinks of the CHECK ENGINE warning light when the proper terminals of the check connector are short-circuited. If the vehicle is equipped with a super monitor display, the diagnostic code is indicated on the display screen.
The CHECK ENGINE warning light will come on when the ignition switch is placed ON and the engine is not running.
When the engine is started, the CHECK ENGINE warning light should go out.
If the light remains on, the diagnosis system has detected a malfunction in the system.