Entering Diagnostic Mode (Self Diagnosis)

Fig. 76 ECCS control unit location.:

Fig. 47 Typical ECCS control unit:

1986

NOTE: It is possible to have false codes contained in the control unit's memory. If more than two malfunction codes exist in the control unit's memory, or any codes at all that do not have any relation to the symptoms the vehicle exhibits, it would be wise to clear the control unit memory and drive the vehicle for enough distance to recreate the code producing problem. At this point, proceed back to step 1 and continue.

1. Ensure mode selector on control unit is turned fully counterclockwise, Fig. 47.
2. Turn ignition switch to On position and ensure inspection lamps on control unit light and remain lit. If not, check harness for battery power and grounds. If all power and ground circuits are OK, stop test, replace control unit and proceed.
3. Turn mode selector fully clockwise, Fig. 47, then depress and release accelerator pedal.
4. On turbocharged 300ZX models, shift transmission from neutral through all gears, then back to neutral.
5. On all models, start engine, then, on models with automatic transmission, apply brakes and shift transmission to Drive.
6. On turbocharged 300ZX models, while driving vehicle at speeds above 6 m.p.h., cycle A/C switch and heater fan switch on and off. Ensure Code 44 (system OK) is displayed. If not, note displayed code(s) and proceed to step 8.
7. On all models except turbocharged 300ZX, cycle any of the following switches on to off: power steering oil pressure switch; A/C, heater switch; headlamp switch; rear defogger switch; radiator fan switch. Ensure Code 44 is displayed. If not, note displayed code(s) and proceed to step 8.
8. Turn mode selector fully counterclockwise and stop engine.
9. Perform diagnosis for codes displayed in step 6 or 7 as described under ``Diagnosis Using Codes.''