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A/C-Cut Control System Circuit: Corolla

  1. If using scan tool, go to next step. If scan tool is not available, go to step  10.
  2. Connect scan tool to data link connector No. 3. See Figure. Turn ignition on. Turn scan tool on. Start engine and turn A/C on. Ensure A/C clutch engages.
  3. Select ACTIVE TEST MODE on scan tool. Check operation of A/C clutch when A/C-cut control is operated by scan tool. A/C clutch should turn off (stop operating) when A/C-cut control is operated by scan tool. If A/C clutch does not operate properly, go to next step. If A/C clutch operates properly, shut engine off. Remove scan tool. Diagnose by symptom. See TROUBLE SHOOTING - NO CODES article.
  4. Check for open or short in wiring harness and electrical connectors between Engine Control Module (ECM) and A/C amplifier. See WIRING DIAGRAMS in MANUAL A/C-HEATER SYSTEMS - COROLLA 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 (ECM) under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - 4-CYLINDER article.
  6. Remove bolts from ECM so electrical connectors can be accessed on ECM. Note ECM electrical connector terminals. See Figure and Figure .
  7. Start engine. On 3-speed A/T and M/T applications, using voltmeter, check voltage between body ground and terminal No. 21 (Red/Blue wire) at ECM electrical connector E6 while turning A/C switch on and off. See Figure. This is the ACT terminal at ECM. On 4-speed A/T applications, using voltmeter, check voltage between body ground and terminal No. 12 (Red/Blue wire) at ECM electrical connector E10 while turning A/C switch on and off. See Figure. This is the ACT terminal at ECM.
  8. On all applications, voltage should be 9-14 volts with A/C switch on, and less than 1.5 volts with A/C switch off. If voltage is as specified, go to next step. If voltage is not as specified, replace A/C amplifier.
  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 (ECM) 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 applications, using voltmeter, check voltage between body ground and terminal No. 21 (Red/Blue wire) at ECM electrical connector E6 while turning A/C switch on and off. See Figure. This is the ACT terminal at ECM. On 4-speed A/T applications, using voltmeter, check voltage between body ground and terminal No. 12 (Red/Blue wire) at ECM electrical connector E10 while turning A/C switch on and off. See Figure. This is the ACT terminal at ECM.
  13. On all applications, voltage should be 9-14 volts with A/C switch on, and less than 1.5 volts with A/C switch off. 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 or short in wiring harness and electrical connectors between ECM and A/C amplifier. See WIRING DIAGRAMS in MANUAL A/C-HEATER SYSTEMS - COROLLA 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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