Lexus IS250 · Service Manual SECURITIES

B278A

Diagnostic trouble codes

DESCRIPTION

This DTC is output when the engine switch power source supply line is open or shorted.
DTC No.
 DTC Detection Condition
 Trouble Area
B278A
 Engine switch power source supply line is open or shorted
  1. Wire harness
  1. Engine switch
  1. Certification ECU

WIRING DIAGRAM

B124191E01

INSPECTION PROCEDURE


1. CHECK WIRE HARNESS (CERTIFICATION ECU - ENGINE SWITCH)
B119109E05

  1. Disconnect the P33 and J31 switch connectors.

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

    Standard resistance:
    Tester Connection
    		 Condition
    		 Specified Condition
    P33-30 (VC5) - J31-14 (VC5)
    		 Always
    		 Below 1 Ω
    P33-40 (AGND) - J31-8 (AGND)
    		 Always
    		 Below 1 Ω
    P33-17 (E) - Body ground
    		 Always
    		 Below 1 Ω
    P33-30 (VC5) - Body ground
    		 Always
    		 10 kΩ or higher
    P33-40 (AGND) - Body ground
    		 Always
    		 10 kΩ or higher



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


2. CHECK HARNESS AND CONNECTOR

  1. B124164E01
    Reconnect P33 ECU and J31 switch connectors.

  1. Measures the voltage according to the value(s) in the table below.

    Standard voltage:
    Tester Connection
    		 Condition
    		 Specified Condition
    P33-30 (VC5) - Body ground
    		 Key is not in cabin
    		 Below 1 V
    Press engine switch
    		 4.6 to 5.4 V



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


3. CHECK HARNESS AND CONNECTOR

  1. B124164E05
    Measures the resistance according to the value(s) in the table below .

    Standard resistance:
    Tester Connection
    		 Condition
    		 Specified Condition
    P33-17 (E) - Body ground
    		 Always
    		 Below 1 Ω



NG
REPLACE CERTIFICATION ECU
OK

REPLACE ENGINE SWITCH


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