DESCRIPTION When there is a
short to GND in the power supply for the transponder key amplifier of
the engine switch, the certification ECU (smart key ECU assembly) stores
this DTC. |
DTC No. | Detection Item |
DTC Detection Condition | Trouble Area |
Note | | B278A |
Short to GND in Immobiliser System Power Source Circuit |
A
short to GND in the power supply of the transponder key amplifier of
the engine switch (VC5 - VC5) detected. (1 trip detection logic*) |
- Engine switch
- Certification ECU (smart key ECU assembly)
- Wire harness or connector
| DTC output confirmation operation:
- With the shift lever in P and the electrical key transmitter
sub-assembly held near the engine switch, an engine start operation is
performed by pressing and holding the engine switch when the transmitter
battery is depleted.
|
- *: Only output while a malfunction is present.
Vehicle Condition and Fail-safe Operation when Malfunction Detected |
Vehicle Condition when Malfunction Detected |
Fail-safe Operation when Malfunction Detected | |
Engine
cannot be started when transmitter battery is depleted by holding
transmitter near engine switch and pressing and holding engine switch
with shift lever in P | - | Related Data List and Active Test |
DTC No. | Data List and Active Test | |
B278A | - | WIRING DIAGRAM
 CAUTION / NOTICE / HINT
NOTICE:
- When using the Techstream with the engine switch off, connect the
Techstream to the DLC3 and turn a courtesy light switch on and off at
intervals of 1.5 seconds or less until communication between the
Techstream and the vehicle begins. Then select the vehicle type under
manual mode and enter the following menus: Body Electrical / Smart Key.
While using the Techstream, periodically turn a courtesy light switch on
and off at intervals of 1.5 seconds or less to maintain communication
between the Techstream and the vehicle.
- The smart key system (for Start Function, Gasoline Model) uses the LIN
communication system and CAN communication system. Inspect the
communication function by following How to Proceed with Troubleshooting.
Troubleshoot the smart key system (for Start Function, Gasoline Model)
after confirming that the communication systems are functioning
properly.
Click here 
- Before replacing the certification ECU (smart key ECU assembly), refer to Registration.
Click here
- After performing repairs, confirm that no DTCs are output by performing "DTC Output Confirmation Operation".
PROCEDURE |
1. | CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) |
(a) Using an oscilloscope, check the waveform.
|
*a | Component with harness connected (Engine Switch) |
- | - |
HINT: Perform this inspection on the engine switch side. Measurement Condition: |
Tester Connection | Condition |
Tool Setting | Specified Condition | |
G41-10 (VC5) - G41-6 (AGND) |
Engine switch off, electrical key transmitter sub-assembly not in cabin, within 30 seconds of engine switch pressed |
2 V/DIV., 200 ms./DIV. |
Pulse generation | OK: The waveform is similar to that shown in the illustration.
| OK |
 | REPLACE ENGINE SWITCH |
|
NG |
 | |
| 2. |
CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - ENGINE SWITCH) |
(a) Disconnect the G40 certification ECU (smart key ECU assembly) connector.
(b) Disconnect the G41 engine switch connector. (c) Measure the resistance according to the value(s) in the table below.
Standard Resistance: |
Tester Connection | Condition |
Specified Condition | |
G40-7 (VC5) - G41-10 (VC5) |
Always | Below 1 Ω | |
G40-11 (AGND) - G41-6 (AGND) |
Always | Below 1 Ω | |
G40-7 (VC5) or G41-10 (VC5) - Other terminals and body ground |
Always | 10 kΩ or higher | |
G40-11 (AGND) or G41-6 (AGND) - Other terminals and body ground |
Always | 10 kΩ or higher |
| NG |
| REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
OK | |
| |
| 3. |
CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) |
(a) Connect the G40 certification ECU (smart key ECU assembly) connector.
(b) Connect the G41 engine switch connector. (c) Measure the voltage according to the value(s) in the table below.
|
*a | Component with harness connected
(Certification ECU (Smart Key ECU Assembly)) |
- | - |
Standard Voltage: |
Tester Connection | Condition |
Specified Condition | |
G40-7 (VC5) - G40-11 (AGND) |
Engine switch off, brake pedal not depressed, 30 seconds or more after driver door opened and then closed |
Below 1 V |
| OK |
| REPLACE ENGINE SWITCH |
| NG |
| REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) | |
