CHECK WIRE HARNESS (POWER SOURCE CIRCUIT)

Turn the ignition switch to the LOCK position.
Disconnect the negative (-) terminal cable from the battery.
Disconnect the connector from the seat belt control ECU.
Connect the negative (-) terminal cable to the battery.
Turn the ignition switch to the ON position.
Measure the voltage according to the value(s) in POWER SOURCE CIRCUIT - VOLTAGE TABLE .

Standard:

POWER SOURCE CIRCUIT - VOLTAGE TABLE

Tester Connection	Condition	Specified Condition
S63-3 (IG1) - Body ground	Ignition switch LOCK -> ON	0 -> 10 to 14 V
S63-9 (+B) - Body ground	Always	10 to 14 V

Fig 1: Checking Wire Harness (Power Source Circuit)

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

NG: REPAIR OR REPLACE WIRE HARNESS (BATTERY - SEAT BELT CONTROL ECU), CHARGING SYSTEM AND BATTERY

OK: Go to next step

CHECK WIRE HARNESS (GROUND CIRCUIT)

Turn the ignition switch to the LOCK position.
Disconnect the negative (-) terminal cable from the battery.
Measure the resistance according to the value(s) in GROUND CIRCUIT - RESISTANCE TABLE .

Standard:

GROUND CIRCUIT - RESISTANCE TABLE

Tester Connection	Condition	Specified Condition
S63-18 (PGND) - Body ground	Always	Below 1 Ω

Fig 2: Checking Wire Harness (Ground Circuit)

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

NG: REPAIR OR REPLACE WIRE HARNESS

OK: REPLACE SEAT BELT CONTROL ECU (See step 10 in REPLACEMENT )

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Inspection Procedure