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 Code |
DTC Detection Condition |
Trouble Area |
DTC Output Confirmation Operation |
---|---|---|---|
B278A |
A short to GND in the power supply of the transponder key amplifier of the engine switch (VC5 - VC5) (1 trip detection logic*). |
|
With the shift lever in P, the key held near the engine switch and an engine start operation is performed by pressing and holding the engine switch when the key battery is depleted. |
Vehicle Condition when Malfunction Detected |
Fail-safe Operation when Malfunction Detected |
---|---|
Engine cannot be started when key battery is depleted by holding key near engine switch and pressing and holding engine switch with shift lever in P |
- |
DTC Code |
Data List and Active Test |
---|---|
B278A |
- |
WIRING DIAGRAM
CAUTION / NOTICE / HINT
NOTICE:
PROCEDURE
1. |
CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) |
(a) Using an oscilloscope, check the waveform.
*a |
Component with harness connected (Engine Switch) |
*b |
Waveform |
HINT:
Perform this inspection on the engine switch side.
Measurement Condition:
Tester Connection |
Condition |
Tool Setting |
Specified Condition |
---|---|---|---|
E28-10 (VC5) - E28-6 (AGND) |
Engine switch off, key not in cabin, within 30 seconds after engine switch pressed |
2 V/DIV., 200 ms./DIV. |
Pulse generation (See waveform) |
OK:
The waveform is similar to that shown in the illustration.
Result
Result |
Proceed to |
---|---|
NG |
A |
OK |
B |
B | ![]() |
REPLACE ENGINE SWITCH |
|
2. |
CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - ENGINE SWITCH) |
(a) Disconnect the C29 certification ECU (smart key ECU assembly) connector.
(b) Disconnect the E28 engine switch connector.
(c) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
Tester Connection |
Condition |
Specified Condition |
---|---|---|
C29-15 (VC5) - E28-10 (VC5) |
Always |
Below 1 Ω |
C29-12 (AGND) - E28-6 (AGND) |
Always |
Below 1 Ω |
C29-15 (VC5) or E28-10 (VC5) - Body ground |
Always |
10 kΩ or higher |
C29-12 (AGND) or E28-6 (AGND) - Body ground |
Always |
10 kΩ or higher |
NG | ![]() |
REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
3. |
CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) |
(a) Reconnect the C29 certification ECU (smart key ECU assembly) connector.
(b) Reconnect the E28 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 |
---|---|---|
C29-15 (VC5) - C29-12 (AGND) |
Engine switch off, brake pedal not depressed, 30 seconds or more elapsed after driver door opened and then closed |
Below 1 V |
OK | ![]() |
REPLACE ENGINE SWITCH |
NG | ![]() |
REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) |
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DESCRIPTION
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WIRING DIAGRAM
CAUTION / NOTICE / HINT
NOTICE:
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PROCEDURE
1.
CHECK HARNESS AN ...