Horn: Diagnosis Lexus LS IV

HOW TO PROCEED WITH TROUBLESHOOTING

HINT

1. Use these procedures to troubleshoot the horn system.
2. *: Use the Techstream.

1. VEHICLE BROUGHT TO WORKSHOP
2. INSPECT BATTERY VOLTAGE Standard voltage: 11 to 14 V If the voltage is below 11 V, recharge or replace the battery before proceeding.
3. CHECK FOR DTC (ELECTRIC POWER CONTROL SYSTEM)* Using the Techstream, check if the electric power control system is functioning normally. Result RESULT CHART Result Proceed to DTC B22B3 is not output A DTC B22B3 is output B B: Go to «ELECTRIC POWER CONTROL SYSTEM»(ref-349751-S42569441112009120800000) A: Go to Next Step
4. INSPECT COMMUNICATION FUNCTION OF CAN COMMUNICATION SYSTEM* Using the Techstream, check if the CAN communication system is functioning normally. Result RESULT CHART Result Proceed to CAN DTC is not output A CAN DTC is output B B: Go to «CAN COMMUNICATION SYSTEM»(ref-349742-S22957258702009120800000) A: Go to Next Step
5. PROBLEM SYMPTOMS TABLE Result RESULT CHART Result Proceed to Fault is not listed in problem symptoms table A Fault is listed in problem symptoms table B B: Go to step 7 A: Go to Next Step
6. OVERALL ANALYSIS AND TROUBLESHOOTING* DATA LIST/ACTIVE TEST (see «DATA LIST/ACTIVE TEST»(ref-349758-S08928661562009120800000) ) Terminals of ECU (see «TERMINALS OF ECU»(ref-349758-S05445370282009120800000) )
7. ADJUST, REPAIR OR REPLACE
8. CONFIRMATION TEST NEXT: END

PROBLEM SYMPTOMS TABLE

HINT

1. Use the table below to help determine the cause of the problem symptom. The potential causes of the symptoms are listed in order of probability in the "Suspected Area" column of the table. Check each symptom by checking the suspected areas in the order they are listed. Replace parts as necessary.
2. Problem symptoms may occur if the electric power control system's functions malfunction. Follow the «HOW TO PROCEED WITH TROUBLESHOOTING»(ref-349758-S39472842692009120800000) procedures. Horn system HORN SYSTEM PROBLEM SYMPTOMS CHART Symptom Suspected Area See Horn does not sound High pitched horn «HIGH PITCHED HORN»(ref-349758-S03398501592009120800000) Low pitched horn «LOW PITCHED HORN»(ref-349758-S21190369752009120800000) Steering pad (Horn button) - Steering pad switch with modulator - Front light ECU - CAN communication system «CAN COMMUNICATION SYSTEM»(ref-349742-S22957258702009120800000) Wire harness «VEHICLE HORN DOES NOT SOUND»(ref-349758-S12750545602009120800000)

Scheme 11

Scheme 12

1. CHECK FRONT LIGHT ECU (FRONT CONTROLLER) Disconnect the A50, A51, A52 and B14 ECU connectors. Measure the resistance and voltage according to the value(s) in the table below. VOLTAGE AND RESISTANCE SPECIFICATION Terminal No. (Symbols) Wiring Color Terminal Description Condition Specified Condition A52-5 (ALTB) - Body ground L - Body ground +B power supply Always 11 to 14 V A52-1 (BATB) - Body ground P - Body ground +B power supply Always 11 to 14 V A50-1 (FMB3) - Body ground LG - Body ground +B power supply Always 11 to 14 V A50-5 (FMIG) - Body ground Y - Body ground IG power supply Engine switch on (IG) 11 to 14 V A50-2 (E) - Body ground W-B - Body ground Ground Always Below 1 ohms If the result is not as specified, there may be a malfunction on the wire harness side. Reconnect the A50, A51, A52 and B14 ECU connectors. Measure the voltage according to the value(s) in the table below. VOLTAGE SPECIFICATION Terminal No. (Symbols) Wiring Color Terminal Description Condition Specified Condition B14-1 (HORL) - Body ground G - Body ground Horn (low pitched) signal Horn is sounding 11 to 14 V B14-2 (HORH) - Body ground G - Body ground Horn (high pitched) signal Horn is sounding 11 to 14 V If the result is not as specified, the ECU may have a malfunction.
2. CHECK STEERING PAD ECU (STEERING PAD SWITCH) Disconnect the z7 ECU connector. Measure the voltage according to the value(s) in the table below. VOLTAGE SPECIFICATION Terminal No. (Symbols) Wiring Color Terminal Description Condition Specified Condition z7-10 (+B) - Body ground B - Body ground +B power supply Always 11 to 14 V If the result is not as specified, there may be a malfunction on the wire harness side.

DTC CHECK/CLEAR

1. CHECK DTC Connect the Techstream to the DLC3. Turn the engine switch on (IG). Turn the Techstream on. Enter the following menus: Body Electrical/Body No. 5/Trouble Codes. Read the DTCs.
2. CLEAR DTC Connect the Techstream to the DLC3. Turn the engine switch on (IG). Turn the Techstream on. Enter the following menus: Body Electrical/Body No. 5/Trouble Codes. Erase the DTCs.

DATA LIST/ACTIVE TEST

1. DATA LIST HINT: Using the Techstream to read the Data List allows the values or states of switches, sensor, actuators and other items to be read without removing any parts. This non-intrusive inspection can be very useful because intermittent conditions or signals may be discovered before parts or wiring is disturbed. Reading the Data List information early in troubleshooting is one way to save diagnostic time. NOTE: In the table below, the values listed under "Normal Condition" are reference values. Do not depend solely on these reference values when deciding whether a part is faulty or not. Connect the Techstream to the DLC3. Turn the engine switch on (IG). Turn the Techstream on. Enter the following menus: Body Electrical/(desired system)/Data List. According to the display on the Techstream, read the "Data List". Body No. 5 BODY NO. 5 DATA LIST REFERENCE Tester Display Measurement Item/Range Normal Condition Diagnostic Note Horn Tr Horn condition/ OK/Heat/Load OK: Horn is normal Heat: ECU is overheated Load: ECU internal short, wire short or horn short - #Codes Number of diagnosis codes
2. ACTIVE TEST HINT: Using the Techstream to perform the Active Tests allows relays, VSVs and actuators and other items to be operated without removing any parts. This non-intrusive functional inspection can be very useful because intermittent operation may be discovered before parts or wiring is disturbed. Performing Active Tests early in troubleshooting is one way to save diagnostic time. Data List information can be displayed while performing Active Tests. Connect the Techstream to the DLC3. Turn the engine switch on (IG). Turn the Techstream on. Enter the following menus: Body Electrical/Body No. 5/Active Test. NOTE: When a Body No. 5 (front light ECU) related vehicle switch is ON, Active Test items related to the vehicle switch are prohibited (double operation prohibition). Check that the vehicle switches are OFF before performing Active Tests. According to the display on the Techstream, perform the "Active Test". Body No. 5 BODY NO. 5 ACTIVE TEST REFERENCE Tester Display Test Part Control Range Horn Relay Operation Vehicle horns ON/OFF

DIAGNOSTIC TROUBLE CODE CHART

HINT

If a trouble code is displayed during the DTC check, inspect the trouble areas listed for that code. For details of the code, refer to the "DTC Code" below.

FRONT LIGHT ECU [Body No. 5]

FRONT LIGHT ECU (BODY NO. 5) DTC CHART