ECU Power Supply Inspection

• Remove the upper air cleaner housing (see Air Cleaner Element Replacement in the Periodic Maintenance chapter).
• Visually inspect the ECU connectors.

If the connector is clogged with mud or dust, blow it off with compressed air.

• Remove the ECU (see ECU Removal).
• Visually inspect the terminals [A] of the ECU connectors.

If the terminals of the main harness connectors are damaged, replace the main harness.

If the terminals of the ECU connectors are damaged, replace the ECU.

• Turn the ignition switch to OFF.
• Disconnect the ECU connectors.

Gray Connector [A]

Set the hand tester [B] to the × 1 Ω range and check the following wiring for continuity.

Special Tool - Hand Tester: 57001-1394

ECU Grounding Inspection

Connections:

(I) BK/Y leads (ECU terminal 40, 73 or 74) ←→ Battery (–) Terminal

(II) Engine Ground ←→ Battery (–) Terminal

Criteria: Both: 0 Ω

If no continuity, check the connectors, the engine ground lead, or main harness, and repair or replace them if necessary.

If the wiring is good, check the power source voltage of the ECU.

NOTE

Be sure the battery is fully charged.

• Connect the ECU connectors
• Connect a digital meter [A] to the connector (gray) [B] with the needle adapter set.

Special Tool - Needle Adapter Set: 57001-1457

ECU Power Supply Inspection Connections:

(I) Digital Meter (+) → Terminal 41 (W/BK)

Digital Meter (–) → Battery (–) terminal

(II) Digital Meter (+) → Terminal 53 (BR/W)

Digital Meter (–) → Battery (–) terminal

(III) Digital Meter (+) → Terminal 54 (W/BK)

Digital Meter (–) → Battery (–) terminal

Ignition Switch OFF:

Terminal 41 (W/BK): Battery Voltage

Terminal 53 (BR/W): 0 V

Terminal 54 (W/BK): Battery Voltage

Ignition Switch ON:

All: Battery Voltage

If the reading is out of the specification, check the following.

Main Fuse 30 A (see Fuse Inspection in the Electrical System chapter)

ECU Fuse 15 A (see Fuse Inspection in the Electrical System chapter)

ECU Main Relay (see Relay Circuit Inspection in the Electrical System chapter)

Power Source Wiring (see wiring diagram in this section)

If the fuse, wiring and relay are good, replace the ECU (see ECU Removal/Installation).