Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Power Source Circuit: Procedure
- CHECK HARNESS AND CONNECTOR (GND CIRCUIT)
- Disconnect the seat belt control ECU connector.
- Measure the resistance according to the value(s) in the table below.
Standard Resistance
Tester Display Condition Specified Condition L2-8 (GND) - Body ground Always Below 1 Ω TEXT IN ILLUSTRATION*1 Front view of wire harness connector
(to Seat Belt Control ECU) - Reconnect the seat belt control ECU connector.
NG → REPAIR OR REPLACE HARNESS OR CONNECTOR (GND CIRCUIT)
OK: Go to next step
- CHECK HARNESS AND CONNECTOR (IG1 CIRCUIT)
- Disconnect the seat belt control ECU connector.
- Turn the power switch on (IG).
- Measure the voltage according to the value(s) in the table below.
Standard Voltage
Tester Display Condition Specified Condition L3-8 (IG1) - L2-8 (PGND) Power switch on (IG) 11 to 14 V TEXT IN ILLUSTRATION*1 Front view of wire harness connector
(to Seat Belt Control ECU)*2 Front view of wire harness connector
(to Seat Belt Control ECU) - Reconnect the seat belt control ECU connector.
NG → See step 4
OK: Go to next step
- CHECK HARNESS AND CONNECTOR (+B CIRCUIT)
- Disconnect the seat belt control ECU connector.
- Measure the voltage according to the value(s) in the table below.
Standard Voltage
Tester Display Condition Specified Condition L2-7 (+B) - Body ground Always 11 to 14 V TEXT IN ILLUSTRATION*1 Front view of wire harness connector
(to Seat Belt Control ECU) - Reconnect the seat belt control ECU connector.
NG → REPAIR OR REPLACE HARNESS OR CONNECTOR (+B CIRCUIT)
OK → See step 8
- INSPECT INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY
- Remove the instrument panel junction block assembly.
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
TEXT IN ILLUSTRATION*1 Instrument Panel Junction Block Assembly - - - Measure the resistance according to the value(s) in the table below.
Standard Resistance
Tester Connection Condition Specified Condition 2E-1 - 2B-16 Always 10 kΩ or higher 2E-1 - 2B-16 When battery voltage applied to terminals 2B-25 and 2B-6 Below 1 Ω - Reinstall the instrument panel junction block assembly.
NG → REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY
OK: Go to next step
- Remove the instrument panel junction block assembly.
- CHECK HARNESS AND CONNECTOR (INSTRUMENT PANEL JUNCTION BLOCK - SEAT BELT CONTROL ECU)
- Disconnect the instrument panel junction block assembly connector.
- Disconnect the seat belt control ECU connector.
- Measure the resistance according to the value(s) in the table below.
Standard Resistance
Tester Connection Condition Specified Condition 2B-16 - L3-8 (IG1) Always Below 1 Ω 2B-16 - Body ground Always 10 kΩ or higher L3-8 (IG1) - Body ground Always 10 kΩ or higher TEXT IN ILLUSTRATION*1 Front view of wire harness connector
(to Seat Belt Control ECU)*2 Front view of wire harness connector
(to Instrument Panel Junction Block Assembly) - Reconnect the seat belt control ECU connector.
- Reconnect the instrument panel junction block assembly connector.
NG → REPAIR OR REPLACE HARNESS OR CONNECTOR (INSTRUMENT PANEL JUNCTION BLOCK - SEAT BELT CONTROL ECU)
OK: Go to next step
- CHECK HARNESS AND CONNECTOR (INSTRUMENT PANEL JUNCTION BLOCK - BODY GROUND)
- Disconnect the instrument panel junction block assembly connector.
- Measure the resistance according to the value(s) in the table below.
Standard Resistance
Tester Connection Condition Specified Condition 2B-6 - Body ground Always Below 1 Ω TEXT IN ILLUSTRATION*1 Front view of wire harness connector
(to Instrument Panel Junction Block Assembly) - Reconnect the instrument panel junction block assembly connector.
NG → REPAIR OR REPLACE HARNESS OR CONNECTOR (INSTRUMENT PANEL JUNCTION BLOCK - BODY GROUND)
OK: Go to next step
- CHECK HARNESS AND CONNECTOR (INSTRUMENT PANEL JUNCTION BLOCK - POWER MANAGEMENT ECU)
- Disconnect the instrument panel junction block assembly connector.
- Disconnect the power management control ECU connector.
- Measure the resistance according to the value(s) in the table below.
Standard Resistance
Tester Connection Condition Specified Condition 2B-25 - L6-2 (IG1D) Always Below 1 Ω 2B-25 - Body ground Always 10 kΩ or higher L6-2 (IG1D) - Body ground</ ptxt> Always 10 kΩ or higher TEXT IN ILLUSTRATION*1 Front view of wire harness connector
(to Power Management control ECU)*2 Front view of wire harness connector
(to Instrument Panel Junction Block Assembly) - Reconnect the power management control ECU connector.
- Reconnect the instrument panel junction block assembly connector.
NG → REPAIR OR REPLACE HARNESS OR CONNECTOR (INSTRUMENT PANEL JUNCTION BLOCK - POWER MANAGEMENT ECU)
OK → REPAIR OR REPLACE HARNESS OR CONNECTOR (INSTRUMENT PANEL JUNCTION BLOCK - BATTERY)
- PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE. Refer to PROBLEM SYMPTOMS TABLE
NO RELATED
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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.