FI/EFI System, page 43

EFI SYSTEM — Troubleshooting for EFI Electronic Circuit with Volt/Ohmmeter    FI-43

No.    Terminal    Trouble    Condition    STD Voltage
8    ISC₁ – ISC₄ — E₁    No voltage    Ignition switch ON    9 — 14V

[CIRCUIT DIAGRAM showing Battery, Fusible Link, Fuse, No. 1 Main Relay, ISC Valve, ECU with terminals ISC₁, ISC₂, ISC₃, ISC₄, +IG S/W, +B, M-REL, E₁]

[DIAGRAM 1] 
Voltmeter connected between ISC₁ (ECU) and E₁, showing ISC₂, ISC₃, ISC₄
FI070

① There is no voltage between ECU terminals ISC₁ — ISC₄ and E₁. (IG S/W ON)

[DIAGRAM 2]
Voltmeter connected to ECU terminal +B
FI076

② Check that there is voltage between ECU terminal +B and body ground. (IG S/W ON)
NO    OK
↓    ↓
Check wiring between computer terminal E₁ and body ground.
OK    BAD
↓    ↓
Try another ECU.    Repair or replace
↓
Refer to No. 1.    NO → Repair or replace
OK
↓
Check wiring between NO. 1 main relay and battery.    BAD → Repair or replace
OK
↓
③ Check ISC valve.

[DIAGRAM 3]
Drawing of ISC valve showing terminals S₁, S₂, S₃, S₄, B₁, B₂ connected to battery
FI077