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Test No. 13: All Return Functions Do Not Operate Or Operate A Little, Then Stop

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  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 .
  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 ECU 25-pin electrical harness connector P21 terminal No. 19 (Brown wire) and positive DVOM lead on power seat ECU 25-pin electrical harness connector P21 terminal No. 25 (White/Green wire). If battery voltage is present, go to step  7. If battery voltage is not present, go to next step.
  5. Disconnect power seat ECU 25-pin electrical harness connector P21. Using an ohmmeter, check continuity of ground circuit between power seat ECU 25-pin electrical harness connector P21 terminal No. 19 (Brown wire) and body ground point located behind right center of instrument panel. See MEMORY SYSTEMS in SYSTEM WIRING DIAGRAMS article. If continuity is less than one ohm, go to next step. If continuity is not less than one ohm, repair or replace wire, harness or connector as required. After repairs have been made, perform confirmation test. See CONFIRMATION TEST .
  6. Check ECU-B (7.5-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 .
  7. 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 good body ground point and positive DVOM lead on terminal No. 5 (Red wire) of power seat ECU 25-pin electrical harness connector P21, monitor voltage while operating any power seat switch. See Figure. If voltage is 7.2-8.8 volts while operating any power seat switch, go to step  9. If voltage is not 7.2-8.8 volts while operating any power seat switch, go to next step.
  8. Disconnect power seat ECU 25-pin electrical harness connector P21. Using an ohmmeter, check for opens and shorts in Red wire between power seat ECU 25-pin electrical harness connector P21 terminal No. 5 and terminal No. 3 of 3-pin electrical harness connector on all four position sensors. See MEMORY SYSTEMS in SYSTEM WIRING DIAGRAMS article. If Red wires, wiring harnesses and connectors are okay, go to next step. If Red wires, wiring harnesses 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 driving position memory switch operation of power seat system. If driving position memory switch operation of power seat system operates properly, original power seat ECU was defective. If driving position memory 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 .
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