LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Lexus >> 2003 >> LS 430 >> Repair and Diagnosis >> External Pages >> Different car >> Section 187 (Power Seats) >> System Tests >> Test No. 11: Memory Function Does Not Operate
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Test No. 11: Memory Function Does 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 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 Figure. See DRIVING POSITION MEMORY 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  4. If circuits do not test as specified, go to next step.
  2. Check driving position memory switch. See DRIVING POSITION MEMORY SWITCH  under COMPONENT TESTS. If driving position memory switch is okay, go to next step.
  3. Disconnect 25-pin electrical harness connector P21 from power seat ECU. Disconnect 4-pin electrical harness connector from driving position memory switch. Using an ohmmeter, check for opens and shorts in wiring harnesses and electrical connectors between power seat ECU and driving position memory switch. See MEMORY SYSTEMS in SYSTEM WIRING DIAGRAMS article. If wires, wiring harness and connectors are okay, go to step  6. 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 .
  4. Turn ignition off. Remove power seat ECU with connectors still attached. See Figure. Using a DVOM, backprobe harness side of power seat ECU 25-pin electrical harness connector P21 with negative DVOM lead on good body ground point and positive DVOM lead on power seat ECU 25-pin electrical harness connector P21 terminal No. 13 (Red/Black wire). With ignition off, no voltage should exist. With ignition on, battery voltage should exist. If voltage is as specified, go to step  6. If voltage is not as specified, go to next step.
  5. Check GAUGE NO. 1 (10-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 .
  6. 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 .
DRIVING POSITION MEMORY SWITCH CIRCUIT TESTING CONNECTIONS

Positive DVOM Lead At Terminal No. (Wire Color) (1) Negative DVOM Lead At Terminal No. (Wire Color) (1)
9 (Green/Yellow) 19 (Brown)
20 (Yellow) 19 (Brown)
21 (Green/Red) 19 (Brown)
(1) Backprobe power seat ECU 25-pin electrical harness connector P21. See Figure.
scientia non olet · About LEMON Manuals