LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Toyota >> 2003 >> Matrix Base, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 149 (Power Seats) >> System Tests >> Test No. 8: All Manual & Return Functions Do Not Operate
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Test No. 8: All Manual & Return Functions Do Not Operate

WARNING: This page is about a different car, the 2002 Toyota Avalon. However, it is still accessible from the selected car via links, so may be relevant.
  1. Turn ignition off. Remove power seat ECU with connectors still attached. See Figure. Using a DVOM, backprobe harness side of power seat ECU 10-pin electrical harness connector P20 with positive DVOM lead on terminal No. 8 (Blue/Orange wire) and negative DVOM lead on terminal No. 7 (White/Black wire). See Fig 1. If battery voltage is present, go to step  4. If battery voltage is not present, go to next step.
  2. Disconnect 10-pin electrical harness connector P20 from power seat ECU. Using an ohmmeter, measure resistance by probing between harness side of 10-pin electrical harness connector terminal No. 7 (White/Black wire) and good body ground point. If resistance is less than one ohm, go to next step. If resistance is not less than one ohm, repair wire, harness or connector between power seat ECU and body ground point located at front of left inner quarter panel. See MEMORY SYSTEMS in SYSTEM WIRING DIAGRAMS article. After repairs have been made, perform confirmation test. See CONFIRMATION TEST .
  3. Check POWER SEAT (30-amp) fuse located in driver side junction block. See Figure. If fuse is okay, go to next step. If fuse is not okay, replace fuse and repair circuit as required. If fuse is okay, check wiring harness and connectors between power seat ECU and battery and repair as necessary. See MEMORY SYSTEMS in SYSTEM WIRING DIAGRAMS article. After repairs have been made, perform confirmation test. See CONFIRMATION TEST .
  4. With power seat ECU removed and connectors still attached, use a DVOM to backprobe harness side of power seat ECU 25-pin electrical harness connector P21 with negative DVOM lead on terminal No. 19 (Brown wire) and positive DVOM lead on specified terminals of ECU 25-pin electrical harness connector P21. See Fig 1. See POWER SEAT CONTROL SWITCH CIRCUIT TESTING CONNECTIONS  table. Battery voltage should exist when ignition is off. No voltage should exist when ignition is on. If circuits test as specified, go to step  7. If circuits do not test as specified, go to next step.
    POWER SEAT CONTROL SWITCH CIRCUIT TESTING CONNECTIONS (1)

    Positive DVOM Lead At Terminal No. (Wire Color) Negative DVOM Lead At Terminal No. (Wire Color)
    6 (Black) 19 (Brown)
    8 (Black/Red) 19 (Brown)
    10 (Green/Black) 19 (Brown)
    11 (Red/Yellow) 19 (Brown)
    12 (Green) 19 (Brown)
    22 (Red/White) 19 (Brown)
    23 (Black/Yellow) 19 (Brown)
    24 (Yellow/Red) 19 (Brown)
    (1) Backprobe power seat ECU 25-pin electrical harness connector P21. See Fig 1.
    Fig 1: Identifying Power Seat ECU Connectors & Terminals For Backprobing Purposes
    G00124426Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  5. Check power seat control switch. See POWER SEAT CONTROL SWITCH  under COMPONENT TESTS. If power seat control switch is okay, go to next step. See MEMORY SYSTEMS in SYSTEM WIRING DIAGRAMS article. After repairs have been made, perform confirmation test. See CONFIRMATION TEST .
  6. Disconnect 25-pin electrical harness connector P21 from power seat ECU. Disconnect Gray 10-pin electrical harness connector P18 from power seat control switch. Using an ohmmeter, check for opens and shorts in wiring harnesses and electrical connectors between power seat ECU and power seat control switch. See MEMORY SYSTEMS in SYSTEM WIRING DIAGRAMS article. If wires, wiring harness and connectors are okay, go to step  9. If wires, wiring harness and connectors are not okay, repair and/or replace as required. After repairs have been made, perform confirmation test. See CONFIRMATION TEST .
  7. Check power seat motors. See POWER SEAT MOTORS  under COMPONENT TESTS. If power seat motors are okay, go to next step.
  8. Disconnect 10-pin electrical harness connector P20 from power seat ECU. Disconnect suspect power seat motor 2-pin electrical harness connector. Using an ohmmeter, check for opens and shorts in wiring harnesses and electrical connectors between power seat ECU and suspect power seat motor. See MEMORY SYSTEMS in SYSTEM WIRING DIAGRAMS article. If wires, wiring harness and connectors are okay, go to next step. If wires, wiring harness and connectors are not okay, repair and/or replace as required. After repairs have been made, perform confirmation test. See CONFIRMATION TEST .
  9. Check power seat ECU ground circuits. If ground circuit resistance is greater than one ohm, repair or replace ground circuit. If ground circuit is okay, substitute original power seat ECU with a known-good unit and recheck manual switch operation of power seat system. If manual switch operation of power seat system operates properly, original power seat ECU was defective. If manual switch operation of power seat system still does not operate properly, perform power seat ECU pin voltage check. See PIN VOLTAGE TESTS . Check wiring harness and electrical connectors for an intermittent problem. Repair wiring harnesses or connectors as necessary. If voltage values, harnesses and connectors are okay, replace power seat ECU. After repairs have been made, perform confirmation test. See CONFIRMATION TEST .
scientia non olet · About LEMON Manuals