DESCRIPTION
WIRING DIAGRAM
INSPECTION PROCEDURE
CHECK WIRE HARNESS (CERTIFICATION ECU - ENGINE SWITCH)
CHECK HARNESS AND CONNECTOR
CHECK HARNESS AND CONNECTOR
DTC B278A Short to GND in Immobiliser System Power Source Circuit
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 | |
WIRING DIAGRAM
INSPECTION PROCEDURE
| 1.CHECK WIRE HARNESS (CERTIFICATION ECU - ENGINE SWITCH) |
Disconnect the P33 and J31 switch connectors.
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 |
| | REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
|
| 2.CHECK HARNESS AND CONNECTOR |
Reconnect P33 ECU and J31 switch connectors.
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 |
| | REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
|
| 3.CHECK HARNESS AND CONNECTOR |
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 |
| | REPLACE CERTIFICATION ECU |
|
|
LEXUS IS250, IS220d / GSE20 ALE20
