B278A

THEFT DETERRENT / KEYLESS ENTRY: ENGINE IMMOBILISER SYSTEM (w/ Smart Key System): B278A: Short to GND in Immobiliser System Power Source Circuit
B278A - Short to GND in Immobiliser System Power Source Circuit

DESCRIPTION

This DTC is stored when the engine switch power source supply line is open or shorted.





WIRING DIAGRAM





INSPECTION PROCEDURE

NOTICE:
If the certification ECU (smart key ECU assembly) is replaced, register the key Engine Immobiliser System (W/ Smart Key System).

PROCEDURE

1. CHECK DTC OUTPUT

(a) Clear the DTCs Engine Immobiliser System (w/ Smart Key System).

(b) Recheck for DTCs Engine Immobiliser System (w/ Smart Key System).

OK:

DTC B278A is not output.

NG -- CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU - ENGINE SWITCH)

OK -- USE SIMULATION METHOD TO CHECK How To Proceed With Troubleshooting

2. CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU - ENGINE SWITCH)

(a) Disconnect the certification ECU (smart key ECU assembly) connector.

(b) Disconnect the engine switch connector.





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

Standard Resistance:





Text in Illustration

Text in Illustration:

NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

3. CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

(a) Reconnect the certification ECU (smart key ECU assembly) connector.

(b) Reconnect the engine switch connector.

(c) Using an oscilloscope, check the waveform.





Waveform (Reference):





OK:

Waveform is output normally (see illustration)

Text in Illustration

Text in Illustration:

NG -- REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) Removal

OK -- REPLACE ENGINE SWITCH Removal