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Test No. 48: Horns Do Not Operate

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.
NOTE: Three different horns are used. One theft deterrent horn is located on passenger side strut tower in engine compartment. Two standard horns are mounted at each side of vehicle, just behind front bumper. Theft deterrent horn is entirely controlled by theft deterrent ECU. Standard horns are controlled either by pushing horn switch or by body control ECU when theft deterrent system has been activated. For testing procedures covering theft deterrent horn and theft deterrent system, see ANTI-THEFT SYSTEMS - AVALON article in ACCESSORIES & EQUIPMENT.
  1. Check HORN fuse (10-amp). HORN fuse is located in engine compartment junction block in front of shock tower at left side of engine compartment. See Figure. If fuse is okay, go to next step. If fuse is defective, repair short in wiring for fuse and replace fuse. See HORN in SYSTEM WIRING DIAGRAMS article. After repairs, perform confirmation test. See CONFIRMATION TEST .
  2. Remove inoperative horn. Horns are mounted at each side of the vehicle, just behind front bumper. Using jumper wires, connect battery voltage and ground at electrical terminals on the horn and check horn operation. If horn operates, go to next step. If horn does not operate, replace horn. After repairs, perform confirmation test. See CONFIRMATION TEST .
  3. Check operation of horn relay. See HORN RELAY  under COMPONENT TESTS. Horn relay is located in engine compartment junction block in front of shock tower at left side of engine compartment. See Figure. If horn relay is okay, go to next step. If horn relay is defective, replace horn relay. After repairs, perform confirmation test. See CONFIRMATION TEST .
  4. Turn ignition off. Separate body control ECU from driver side junction block. See BODY CONTROL ELECTRONIC CONTROL UNIT  under REMOVAL & INSTALLATION. Using a DVOM, check voltage reading between 12-pin driver side junction block-to-body control ECU connector terminal No. 10 and good body ground point. See Figure. See HORN in SYSTEM WIRING DIAGRAMS article. With horn button depressed, voltage should be below 1 volt; with horn button released, voltage should be 10-14 volts. Check Black wire between battery and horn relay. See POWER DISTRIBUTION in SYSTEM WIRING DIAGRAMS article. Voltage should be 10-14 volts. If wires, harnesses and connectors are okay, go to next step. If wires, harnesses or connectors are not okay, repair as required. After repairs, perform confirmation test. See CONFIRMATION TEST .
  5. Check wiring harnesses and electrical connectors between battery and engine compartment junction block, between engine compartment junction block and driver side junction block, between engine compartment junction block and horns, between driver side junction block and body control ECU, and all power and ground connections. See HORN and POWER DISTRIBUTION in SYSTEM WIRING DIAGRAMS article. If wiring harnesses or electrical connectors are defective, repair as necessary. After repairs, perform confirmation test. See CONFIRMATION TEST .
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