Test B: Power Seat Control Switch Circuit

Remove power seat control ECU from under driver's seat, with harness connectors still connected. Ensure ignition switch is off. Using a DVOM, backprobe connector P21 terminal No. 19 with negative lead, and terminals No. 6, 8, 10, 11, 12, 22, 23 and 24, individually with positive lead of DVOM. See Fig 1. If voltage is 10-14 volts at each terminal, go to TEST C: MOTOR CIRCUIT . If voltage is not 10-14 volts at each terminal, go to next step.

Fig 1: Identifying ECU Connector P21 Terminals (Avalon)
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Remove driver's seat. Disconnect power seat control switch. Using an ohmmeter, operate switch and check for continuity between switch terminals for each switch and each switch position listed in table. See POWER SEAT CONTROL SWITCH CONTINUITY TEST (AVALON) table. If continuity does not exist between each terminal listed, replace switch. If continuity does exist between each terminal listed, go to next step.

POWER SEAT CONTROL SWITCH CONTINUITY TEST (AVALON)

Switch Position

Terminals No. ⁽¹⁾

Driver's Seat Slide Switch

Front

1 & 9

Back

1 & 6

Driver's Seat Front Vertical Switch

1 & 5

Down

1 & 10

Driver's Seat Lifter Switch

1 & 8

Down

1 & 7

Driver's Seat Reclining Switch

Forward

1 & 3

Rear

1 & 2

Passenger Slide Switch

Front

1 & 9

Back

1 & 6

Passenger Front Vertical Switch

1 & 10

Down

1 & 5

Passenger Lifter Switch

1 & 7

Down

1 & 8

Passenger Reclining Switch

Forward

1 & 3

Rear

1 & 2

⁽¹⁾	See Figure.

Check harness and connectors between power seat control ECU and power seat control switch for defects, damage or poor connections. If defects are found, repair as necessary and retest circuit to verify repair. If defects were not found, go to next step.
Replace power seat control ECU, and retest circuit to verify repair.