Test No. 21: Automatic Light Control System Does Not Operate
NOTE:
Automatic light control system turns on or off the headlights, park lights, taillights, side marker lights and instrument panel lights according to darkness of surrounding lighting. Headlight control switch must be position No. 3 (AUTO position) for automatic light control system to operate.
- Check operation of automatic light control system and automatic light control sensor. See AUTOMATIC LIGHT CONTROL SYSTEM & AUTOMATIC LIGHT CONTROL SENSOR under COMPONENT TESTS. If automatic light control system and automatic light control sensor operates properly, go to next step. If automatic light control sensor does not operate properly, replace automatic light control sensor and recheck automatic light control system operation.
- Check wiring harness and electrical connectors between automatic light control sensor and body Electronic Control Unit (ECU) for an intermittent problem. See WIRING DIAGRAMS in HEADLIGHT SYSTEMS article or WIRING DIAGRAMS in DAYTIME RUNNING LIGHTS article. Body ECU is located behind driver's side of instrument panel and contains 3 electrical connectors. See Figure. If wiring harness and electrical connector are okay, go to next step. If wiring harness or electrical are defective, repair as necessary and recheck automatic light control system operation.
- It may be possible that automatic light control sensor is defective or has an intermittent problem. Replace automatic light control sensor and recheck automatic light control system operation. If automatic light control system and automatic light control sensor does not operate properly, go to next step. If automatic light control system and automatic light control sensor operate properly, the original automatic light control sensor was defective.
- If Toyota hand-held tester is available, go to next step. If Toyota hand-held tester is not available, go to step 6.
- Connect hand-held tester to Data Link Connector (DLC) No. 3. See Figure. Using hand-held tester manufacturer's instructions, check operation of headlight control switch while using the DATA LIST. Check that proper displays for headlight control switch are obtained on hand-held tester to verify proper headlight control switch operation. See HEADLIGHT CONTROL SWITCH DISPLAY table. If proper displays for headlight control switch are not obtained on hand-held tester, remove hand-held tester. Go to next step. If proper displays for headlight control switch are obtained on hand-held tester, remove hand-held tester. Go to step 8.HEADLIGHT CONTROL SWITCH DISPLAY
Headlight Control Switch Position Hand-Held Test Display OFF Tail (Headlight Switch) OFF Head (Headlight Switch) OFF "A" (Auto Light Switch) OFF TAIL Tail (Headlight Switch) ON Head (Headlight Switch) OFF "A" (Auto Light Switch) OFF HEAD Tail (Headlight Switch) ON Head (Headlight Switch) ON "A" (Auto Light Switch) OFF AUTO Tail (Headlight Switch) OFF Head (Headlight Switch) OFF "A" (Auto Light Switch) ON - Check headlight control switch. See HEADLIGHT CONTROL SWITCH under COMPONENT TESTS. If headlight control switch is okay, go to next step. If headlight control switch is defective, replace headlight control switch and recheck automatic light control system operation. See HEADLIGHT CONTROL SWITCH under REMOVAL & INSTALLATION.
- Check wiring harness and electrical connectors between headlight control switch and body ECU. See WIRING DIAGRAMS in HEADLIGHT SYSTEMS article or WIRING DIAGRAMS in DAYTIME RUNNING LIGHTS article. If wiring harness and electrical connectors are okay, go to next step. If wiring harness or electrical are defective, repair as necessary and recheck automatic light control system operation.
- Check body ECU for proper voltage and input signals. See BODY ELECTRONIC CONTROL UNIT under PIN VOLTAGE TESTS. If proper voltage and input signals exist, go to next step. If proper voltage and input signals do not exist, repair as necessary and recheck automatic light control system operation.
- Replace body ECU with a known-good body ECU and recheck automatic light control system operation. If automatic light control system operates properly, original body ECU was defective. If automatic light control system still does not operate properly, check wiring harness and electrical connectors for body ECU for an intermittent problem. See WIRING DIAGRAMS in HEADLIGHT SYSTEMS article or WIRING DIAGRAMS in DAYTIME RUNNING LIGHTS article. Repair wiring harness or electrical connector as necessary.