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A/C-Cut Control System Circuit: Corolla

  1. If Toyota hand-held tester is available, go to next step. If Toyota hand-held tester is not available, go to step  10.
  2. Connect hand-held tester to data link connector No. 3 at driver's side of instrument panel. See Figure. Turn ignition on and then turn hand-held tester on. Start engine and turn A/C switch to ON position. Ensure A/C clutch engages.
  3. Select ACTIVE TEST MODE on hand-held tester. Check operation of A/C clutch when A/C-cut control is operated by hand-held tester. A/C clutch should turn off (stop operating) when A/C-cut control is operated by hand-held tester. If A/C clutch does not operate properly, go to next step. If A/C clutch operates properly, shut engine off. Remove hand-held tester. Diagnose by symptom. See TROUBLE SHOOTING - NO CODES article.
  4. Check for open and short in wiring harness and electrical connectors between Engine Control Module (ECM) and A/C amplifier. See WIRING DIAGRAMS in appropriate article in AIR CONDITIONING & HEATING. ECM is located behind stereo on instrument panel, just in front of center console. For illustration of ECM location, see THEORY & OPERATION article. A/C amplifier is located behind instrument panel, just above glove box, near center of glove box area. See Fig 1. If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical connector is defective, repair as necessary.
  5. Remove necessary components for access to ECM. See ENGINE CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article.
  6. Remove bolts from ECM so electrical connectors can be accessed. Note ECM electrical connector terminals. See Figure and Figure .
  7. Start engine. On 3-speed A/T and M/T models, using voltmeter, check voltage between body ground and terminal No. 21 (Red/Blue wire) at ECM electrical connector E6 while turning A/C switch from ON to OFF positions. See Figure. This is the ACT terminal at ECM. On 4-speed A/T models, using voltmeter, check voltage between body ground and terminal No. 12 (Red/Blue wire) at ECM electrical connector E10 while turning A/C switch from ON to OFF positions. See Figure. This is the ACT terminal at ECM.
  8. On all models, voltage should be 9-14 volts with A/C switch in ON position and less than 1.5 volts with A/C switch in OFF position. If voltage is as specified, go to next step. If voltage is not as specified, check for open and short in wiring harness and electrical connectors between ECM and A/C amplifier. See WIRING DIAGRAMS in appropriate article in AIR CONDITIONING & HEATING. A/C amplifier is located behind instrument panel, just above glove box, near center of glove box area. See Fig 1. If wiring harness and electrical connectors are okay, replace A/C amplifier. If wiring harness or electrical connector is defective, repair as necessary.
  9. Check ECM ground circuit. See WIRING DIAGRAMS article. If ECM ground circuit is defective, repair ground circuit as necessary. If ECM ground circuit is okay, replace ECM.
    Fig 1: Locating A/C Amplifier (Corolla)
    G99I52389Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  10. Remove necessary components for access to Engine Control Module (ECM). See ENGINE CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article.
  11. Remove bolts from ECM so electrical connectors can be accessed on ECM. Note ECM electrical connector terminals. See Figure and Figure .
  12. Start engine. On 3-speed A/T and M/T models, using voltmeter, check voltage between body ground and terminal No. 21 (Red/Blue wire) at ECM electrical connector E6 while turning A/C switch from ON to OFF positions. This is the ACT terminal at ECM. On 4-speed A/T models, using voltmeter, check voltage between body ground and terminal No. 12 (Red/Blue wire) at ECM electrical connector E10 while turning A/C switch from ON to OFF positions. This is the ACT terminal at ECM.
  13. On all models, voltage should be 9-14 volts with A/C switch in ON position and less than 1.5 volts with A/C switch in OFF position. If voltage is not as specified, go to next step. If voltage is as specified, check ECM ground circuit. See WIRING DIAGRAMS article. If ECM ground circuit is defective, repair ground circuit as necessary. If ECM ground circuit is okay, replace ECM.
  14. Check for open and short in wiring harness and electrical connectors between ECM and A/C amplifier. See WIRING DIAGRAMS in appropriate article in AIR CONDITIONING & HEATING. A/C amplifier is located behind instrument panel, just above glove box, near center of glove box area. See Fig 1. If wiring harness and electrical connectors are okay, replace A/C amplifier. If wiring harness or electrical connector is defective, repair as necessary.
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