Inspection Procedure

WARNING: This page is about a different car, the 2006 Lexus IS 350 and 2006 Lexus IS 250. However, it is still accessible from the selected car via links, so may be relevant.

CHECK CAN BUS LINE FOR OPEN (SEAT BELT CONTROL ECU BRANCH LINE)

Turn the engine switch off.
Disconnect the seat belt control ECU connector (Q38).

Measure the resistance according to the value(s) in CAN BUS LINE FOR OPEN (SEAT BELT CONTROL ECU BRANCH LINE) .

Standard resistance

CAN BUS LINE FOR OPEN (SEAT BELT CONTROL ECU BRANCH LINE)

Tester Connection	Condition	Specified Value
Q38-4 (CANH) - Q38-6 (CANL)	Engine switch off	54 to 69°F

Fig 1: Identifying Q38 Connector Terminals

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NG: REPAIR OR REPLACE SEAT BELT CONTROL ECU BRANCH LINE OR CONNECTOR (CAN-H, CAN-L)

OK: Go to next step.

CHECK WIRE HARNESS (IG1, PGND)

Measure the resistance according to the value(s) in WIRE HARNESS (IG1, PGND) (RESISTANCE) .

Standard resistance

WIRE HARNESS (IG1, PGND) (RESISTANCE)

Tester Connection	Condition	Specified Value
Q38-18 (PGND) - Body ground	Always	Below 1 ohms

Measure the voltage according to the value(s) in WIRE HARNESS (IG1, PGND) (VOLTAGE) .

Standard voltage

WIRE HARNESS (IG1, PGND) (VOLTAGE)

Tester Connection	Condition	Specified Value
Q38-3 (IG1) - Body ground	Engine switch on (IG)	10 to 14 V

Fig 2: Checking Wire Harness (IG1, PGND)

NG: REPAIR OR REPLACE HARNESS OR CONNECTOR

OK: REPLACE SEAT BELT CONTROL ECU