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