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Test No. 14: One Return Function Does Not Operate Or Operates A Little, Then Stops

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. Test suspect motor and position sensor one at a time by disconnecting 2-pin electrical harness motor connector and 3-pin position sensor electrical harness connector from suspect motor. See IDENTIFYING POWER SEAT MOTOR & POSITION SENSOR CONNECTORS  table. See MEMORY SYSTEMS in SYSTEM WIRING DIAGRAMS article.
  2. Using jumper wires, connect positive battery voltage to suspect position sensor terminal No. 3 and negative battery voltage to suspect position sensor terminal No. 2. See Fig 1.
  3. Connect DVOM positive lead to position sensor terminal No. 1 and DVOM negative lead to good body ground point. Measure position sensor voltage while applying battery voltage to respective power seat motor terminals. Power seat motor terminal polarity connections are of no concern during this test. See Fig 1.
  4. With motor turning, voltage reading should be 5-7 volts. When motor stops, voltage reading should be zero or 10-14 volts, depending on position where motor stops. Check voltage with motor stopped in several different positions to ensure sensor output changes with motor position. If voltage readings are as specified, go to next step. If voltage readings are not as specified, replace suspect power seat motor assembly. See POWER SEAT MOTORS  under REMOVAL & INSTALLATION. After repairs have been made, perform confirmation test. See CONFIRMATION TEST .
  5. Disconnect power seat ECU 25-pin electrical harness connector P21 and suspect position sensor 3-pin electrical harness connector. Using an ohmmeter, check for opens and shorts in wiring, harness and connectors between power seat ECU and suspect position sensor. See MEMORY SYSTEMS in SYSTEM WIRING DIAGRAMS article. If wires, wiring harnesses and connectors are okay, go to next step. If 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 .
  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 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 .
IDENTIFYING POWER SEAT MOTOR & POSITION SENSOR CONNECTORS

Power Seat Motor 2-Pin Motor Electrical Harness Connector Color 3-Pin Position Sensor Electrical Harness Connector Color (1)
Front Vertical Motor (Driver Seat Only) Blue Blue
Rear Vertical Motor Green Green
Recline Motor Milky White Milky White
Slide Motor Orange Orange
(1) Models with driving position memory only.
Fig 1: Testing Power Seat Motor Position Sensors
G00124428Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
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