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*1) |
|
DTC output confirmation operation:
|
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 |
- |
DTC No. |
Data List and Active Test |
---|---|
B278A |
- |
WIRING DIAGRAM
Refer to B2784.
Click here
CAUTION / NOTICE / HINT
NOTICE:
Click here
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 |
---|---|---|---|
F59-10 (VC5) - F59-6 (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 |
|
2. |
CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - ENGINE SWITCH) |
(a) Disconnect the F1 certification ECU (smart key ECU assembly) connector.
(b) Disconnect the F59 engine switch connector.
(c) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
Tester Connection |
Condition |
Specified Condition |
---|---|---|
F1-7 (VC5) - F59-10 (VC5) |
Always |
Below 1 Ω |
F1-11 (AGND) - F59-6 (AGND) |
Always |
Below 1 Ω |
F1-7 (VC5) or F59-10 (VC5) - Body ground |
Always |
10 kΩ or higher |
F1-11 (AGND) or F59-6 (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 F1 certification ECU (smart key ECU assembly) connector.
(b) Reconnect the F59 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 |
---|---|---|
F1-7 (VC5) - F1-11 (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) |
Toyota CH-R Service Manual > Immobiliser System(w/ Smart Key System): Dtc Check / Clear
DTC CHECK / CLEAR
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 u ...
Toyota CH-R Service Manual > Immobiliser System(w/ Smart Key System): Diagnostic Trouble Code Chart
DIAGNOSTIC TROUBLE CODE CHART
Immobiliser System
DTC No.
Detection Item
Link
B2779
Engine Starter Communication Malfunction
B2784
Antenna Coil Open / Short
B278A
...