DESCRIPTION The front seat belt buckle switch LH circuit consists of the airbag ECU assembly and front seat belt buckle switch LH (front seat inner belt assembly LH). DTC B1656 is stored when a malfunction is detected in the front seat belt buckle switch LH circuit.
WIRING DIAGRAM  CAUTION / NOTICE / HINT NOTICE: After turning the engine switch off, waiting time may be required before disconnecting the cable from the negative (-) battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) battery terminal notices before proceeding with work. Click here
PROCEDURE
(a) Turn the engine switch off. (b) Disconnect the cable from the negative (-) battery terminal. CAUTION: Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system. (c) Check that the connectors are properly connected to the airbag ECU assembly and front seat inner belt assembly LH. OK: The connectors are properly connected.
(a) Disconnect the connectors from the airbag ECU assembly and front seat inner belt assembly LH. (b) Check that the terminals of the connectors are not deformed or damaged. OK: The terminals are not deformed or damaged.
(a) Connect the cable to the negative (-) battery terminal. 
(b) Turn the engine switch on (IG). (c) Measure the voltage according to the value(s) in the table below. Standard Voltage: w/o Seat Position Memory System:
(d) Turn the engine switch off. (e) Disconnect the cable from the negative (-) battery terminal. CAUTION: Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system. (f) Using a service wire, connect terminals 28 (LBE+) and 27 (LBE-) of connector B. NOTICE: Do not forcibly insert the service wire into the terminals of the connector when connecting the wire. (g) Measure the resistance according to the value(s) in the table below. Standard Resistance: w/o Seat Position Memory System:
(h) Disconnect the service wire from connector B. (i) Measure the resistance according to the value(s) in the table below. Standard Resistance: w/o Seat Position Memory System:
(b) Connect the cable to the negative (-) battery terminal. (c) Turn the engine switch on (IG), and wait for at least 60 seconds. (d) Clear the DTCs stored in memory. Body Electrical > SRS Airbag > Clear DTCs(e) Turn the engine switch off. (f) Turn the engine switch on (IG), and wait for at least 60 seconds. (g) Check for DTCs. Body Electrical > SRS Airbag > Trouble CodesOK: DTC B1656 is not output. HINT: Codes other than DTC B1656 may be output at this time, but they are not related to this check.
(b) Disconnect the cable from the negative (-) battery terminal. CAUTION: Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system. (c) Replace the front seat inner belt assembly LH with a known good one. Click here HINT: Perform the following inspection using known good parts from another vehicle if possible. (d) Connect the cable to the negative (-) battery terminal. (e) Turn the engine switch on (IG), and wait for at least 60 seconds. (f) Clear the DTCs stored in memory. Body Electrical > SRS Airbag > Clear DTCs(g) Turn the engine switch off. (h) Turn the engine switch on (IG), and wait for at least 60 seconds. (i) Check for DTCs. Body Electrical > SRS Airbag > Trouble CodesOK: DTC B1656 is not output. HINT: Codes other than DTC B1656 may be output at this time, but they are not related to this check. (j) Turn the engine switch off. (k) Disconnect the cable from the negative (-) battery terminal. CAUTION: Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system. (l) Restore the front seat inner belt assembly LH that was installed for testing to its original location. Click here
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Toyota Avalon (XX50) 2019-2022 Service & Repair Manual > Heated Steering Wheel System(for Gasoline Model): Problem Symptoms Table
PROBLEM SYMPTOMS TABLE HINT: Use the table below to help determine the cause of problem symptoms. If multiple suspected areas are listed, the potential causes of the symptoms are listed in order of probability in the "Suspected Area" column of the table. Check each symptom by checking the suspected ...
