Toyota 4Runner Quiz
Vehicle Exterior

Light Sensor Circuit Malfunction (B1244)

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DESCRIPTION

The automatic light control sensor detects ambient light, converts it into an electrical signal, and outputs it to the main body ECU. The main body ECU turns on or off the headlights and taillights according to the signal.

DTC Code

DTC Detection Condition

Trouble Area

B1244
  • Malfunction in automatic light control sensor.
  • Open or short in automatic light control sensor circuit.
  • Automatic light control sensor
  • Main body ECU (multiplex network body ECU)
  • Harness or connector
WIRING DIAGRAM
PROCEDURE

  1. CHECK FOR DTC

(a) Clear the DTCs (See page ).


(b) Check for DTCs (See page ).


OK:

DTC B1244 output does not occur.


OK

USE SIMULATION METHOD TO CHECK
NG

  1. READ VALUE USING TECHSTREAM (AUTOMATIC LIGHT CONTROL SENSOR)

(a) Using the Techstream, read the Data List (See page ).


Main Body

Tester Display

Measurement Item/Range

Normal Condition

Diagnostic Note

Illumination Rate Info

Illumination rate information / 0 ms. to 99.99 ms.

Value is output according to ambient light levels

-

OK:

Normal condition listed above is displayed.


OK

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)
NG

  1. CHECK HARNESS AND CONNECTOR (MAIN BODY ECU - AUTOMATIC LIGHT CONTROL SENSOR)

(a) Disconnect the F9 main body ECU connector.

(b) Disconnect the G2 automatic light control sensor connector.

(c) Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection

Condition

Specified Condition

F9-22 (CLTE) - G2-3 (CLTE)

Always

Below 1 Ω

F9-21 (CLTS) - G2-5 (CLTS)

Always

Below 1 Ω

F9-20 (CLTB) - G2-6 (CLTB)

Always

Below 1 Ω

F9-22 (CLTE) - Body ground

Always

10 kΩ or higher

F9-21 (CLTS) - Body ground

Always

10 kΩ or higher

F9-20 (CLTB) - Body ground

Always

10 kΩ or higher

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

  1. CHECK MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

(a) Reconnect the F9 main body ECU connector.

(b) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

F9-20 (CLTB) - F9-22 (CLTE)

Ignition switch off

Below 1 V

Ignition switch ON

11 to 14 V
Text in Illustration

*a

Component with harness connected

(Main Body ECU)

NG

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)
OK

  1. CHECK AUTOMATIC LIGHT CONTROL SENSOR

(a) Reconnect the G2 automatic light control sensor connector.

(b) Connect an oscilloscope to the automatic light control sensor connector.

(c) Check the waveform.

OK:

Tester Connection

Tool Setting

Switch Condition

Specified Condition

G2-3 (CLTE) - G2-5 (CLTS)

5 V/DIV., 5 ms./DIV.

Ignition switch ON, headlight dimmer switch in AUTO position

Correct waveform is as shown
Text in Illustration

*a

Component with harness connected

(Automatic Light Control Sensor)

HINT:

If the ambient light becomes brighter, width A becomes narrower.

OK

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

NG

REPLACE AUTOMATIC LIGHT CONTROL SENSOR

Test yourself

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