Input Codes

Fig. 5 Fault code explanation:

Both the ignition control unit and the fuel injection control unit are equipped with a memory for recording operational faults. These systems constantly monitor the operation of the sensors, wiring, and all input signals. If a signal is received, by either control unit, that is outside of a pre-programmed 'normal' range, the control unit will do two things:
1. It will take corrective action by determining a default value (a normal operating range)
2. It will record the problem in memory, and display this information as a 'fault code' on the engine warning light in the instrument cluster.
Faults in the fuel and ignition systems can be read from the blinking code of the warning light on the instrument panel after activating the diagnostic procedure.
Each fault code consists of 4 blink pulse groups of up to 4 blink pulses each. Between each group of blink pulses there is a pause of about 2.5 seconds.
The various fault codes are read by counting the number of pulses in each group (1 to 4), and then combining the 4 groups. See Fig. 5.
Once the diagnostic procedure is activated, the display will proceed as follows:
1. Starting signal (light on 2.5 sec)
2. Pause (light off 2.5 sec)
3. Transmission of the 4 impulse groups
4. After the fourth impulse group, a 2.5 sec. pause (light off)
5. Repeat the fault code.
The same fault will be repeated until the next fault in the memory is activated by bridging the terminals on top of the fuel pump relay with a fuse.



The fault code functions are different for 49 state and California cars.
In the 49 state version, the fault code memory is erased each time the ignition is switched OFF.
In the California version, the engine warning light will flash whenever an emissions related fault occurs, and will stay ON until the problem is corrected and the memory intentionally erased.
Non-emissions related faults will be displayed only when the fault code procedure is activated.