Mode IV (Switches ON/OFF Diagnostic System)

1. Access the ECU from the floor board in front of the center console and position it for observing the diodes.
2. Turn the ignition key on, do not start the engine.

Fig. 52 Selecting Modes:

3. Turn the diagnostic mode selector on the ECU fully clockwise until both diodes flash 4 times then turn the selector fully counterclockwise. The ECCS system is now in mode 4.
4. Make sure the RED diode goes off.
5. Make sure the RED diode lights when the accelerator pedal is depressed.
If not, inspect the idle switch circuit in ELECTRICAL AND COMPONENT CIRCUIT DIAGNOSIS and repair as necessary.
6. Make sure the RED diode lights when starting the engine.
If not, inspect the start signal circuit in ELECTRICAL AND COMPONENT CIRCUIT DIAGNOSIS and repair as necessary.
7. Lift the drive wheels off of the ground.
8. Make sure the GREEN diode lights when the vehicle speed is over 12 m.p.h. (20 km/h).
If not, inspect as per CODE 14 VEHICLE SPEED SENSOR in DIAGNOSTIC CHARTS and repair as necessary.
9. Turn the ignition switch off. Turning the engine off will return the ECCS system to "Mode 1" (normal operating mode).