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Home >> Subaru >> 1997 >> Legacy Outback Limited, Automatic >> Repair and Diagnosis (Single Page) >> Transmission >> Automatic Trans >> Diagnosis - 4-Speed - With 2-Digit DTCS >> Diagnostic Tests >> DTC 21: ATF Temperature Sensor >> 1997-98 Impreza, 1997-98 Legacy & 1998 Forester

1997-98 Impreza, 1997-98 Legacy & 1998 Forester

  1. Turn ignition switch to OFF position. Disconnect connector from transmission and TCM. Measure resistance between TCM connector B54 and transmission connector. Resistance between connector B54 terminal No. 10 and transmission connector terminal No. 5 should be 0-1 ohm. If resistance is okay, go to next step. If resistance is not within specification, repair open in harness between TCM and transmission connector.
  2. Measure resistance between TCM connector B56 and transmission connector. Resistance between connector B56 terminal No. 20 and transmission connector terminal No. 12 should be 0-1 ohm. If resistance is okay, go to next step. If resistance is not within specification, repair open in harness between TCM and transmission connector.
  3. Measure resistance between TCM connector B54 and ground. Resistance between connector B54 terminal No. 10 and ground should be more than 100 k/ohms. If resistance is okay, go to next step. If resistance is not within specification, repair short to ground in harness between TCM and transmission connector.
  4. Measure resistance between TCM connector B56 and ground. Resistance between connector B56 terminal No. 20 and ground should be more than 100 k/ohms. If resistance is okay, go to next step. If resistance is not within specification, repair short to ground in harness between TCM and transmission connector.
  5. Ensure ignition switch is in OFF position and connect all connectors to transmission and TCM. Start engine and warm-up engine to operating temperature. ATF must reach 176° F (80° C). Measure resistance between transmission connector terminals. Resistance between transmission connector terminals No. 12 and No. 5 should be 272-374 ohm. If resistance is okay, go to next step. If resistance is not within specification, go to step  13.
  6. With KOEO, back probe and measure resistance between transmission connector terminals. Resistance between transmission connector terminals No. 12 and No. 5 should increase while oil temperature decreases. If resistance increases normally, go to next step. If resistance does not increase as oil temperature decreases, go to step  13.
  7. Warm-up ATF to operating temperature. Back probe and measure voltage between TCM B54 and connector B56 terminals. Voltage between connector B54 terminal No. 10 and connector B56 terminal No. 20 should be 2.9- 4.0 volts. If voltage is okay, go to next step. If voltage is not within specification, go to step  9.
  8. With KOEO, back probe and measure voltage between TCM B54 and connector B56 terminals. Voltage between connector B54 terminal No. 10 and connector B56 terminal No. 20 should be 1.0-1.4 volts. If voltage is okay and AT OIL TEMP light illuminates, concern is intermittent and circuit has returned to normal condition. A temporary poor contact of connector or harness may be cause. Repair TCM harness or connector. If voltage is not within specification, go to next step.
  9. Check for poor contact in ATF temperature sensor circuit. If contact is poor, repair as necessary. If contact is okay, replace TCM and retest.
  10. Turn ignition switch to OFF position. Remove transmission connector from bracket. Drain transmission fluid when cool. Remove oil pan and disconnect connector from ATF temperature sensor. Measure resistance between ATF temperature sensor connector and ground. Resistance between ATF temperature sensor connector terminal No. 2 and ground should be 1.5-4.5 ohms. If resistance is okay, go to next step. If resistance is not within specification, replace ATF temperature sensor.
  11. Disconnect connector from transmission. Measure resistance between ATF temperature sensor and transmission connector receptacle. Resistance between ATF temperature sensor connector terminal No. 1 and transmission connector receptacle terminal No. 12 should be 0-1 ohm. If resistance is okay, go to next step. If resistance is not within specification, repair open in internal transmission harness between ATF temperature sensor connector and transmission connector receptacle.
  12. Measure resistance between ATF temperature sensor and transmission connector receptacle. Resistance between ATF temperature sensor connector terminal No. 2 and transmission connector receptacle terminal No. 5 should be 0-1 ohm. If resistance is okay, go to next step. If resistance is not within specification, repair open in internal transmission harness between ATF temperature sensor connector and transmission connector receptacle.
  13. Measure resistance between transmission connector receptacle and ground. Resistance between transmission connector receptacle terminal No. 5 and ground should be more than 100 k/ohms. If resistance is okay, go to next step. If resistance is not within specification, repair short to ground in internal transmission harness between ATF temperature sensor connector and transmission connector receptacle.
  14. Measure resistance between transmission connector receptacle and ground. Resistance between transmission connector receptacle terminal No. 12 and ground should be more than 100 k/ohms. If resistance is okay and AT OIL TEMP light illuminates, concern is intermittent and circuit has returned to normal condition. A temporary poor contact of connector or harness may be cause. Repair harness to, or connector in ATF temperature sensor or transmission connector. If resistance is not within specification, repair short to ground in internal transmission harness between ATF temperature sensor connector and transmission connector receptacle.
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