DTC C0040:23 [START STOP UNIT]

id0902p6021100

System malfunction location

Brake switch (No.1 signal) circuit malfunction
Detection condition
•  With the ignition switched ON (engine off or on), the start stop unit detects that the brake switch No.1 signal is in the off condition for 3 s or more continuously for a continuous 5 times even though brake switch No.2 signal changes.
Fail-safe
•  Determined by brake switch No.2 with the brake pedal depressed.
Possible cause
•  Brake switch connector or terminal malfunction
•  Brake switch (No.1 signal) malfunction
•  Brake switch (No.1 signal) power supply circuit malfunction
―  Short to ground in wiring harness between STOP 10 A fuse and brake switch terminal A
―  STOP 10 A fuse malfunction
―  Open circuit in wiring harness between battery positive terminal and brake switch terminal A
•  Start stop unit connector or terminal malfunction
•  Short to ground in wiring harness between brake switch terminal D and start stop unit terminal 1C
•  Open circuit in wiring harness between brake switch terminal D and start stop unit terminal 1C
•  Start stop unit malfunction

Diagnostic Procedure

Step

Inspection

Action
1
INSPECT BRAKE SWITCH CONNECTOR CONDITION
•  Switch the ignition to off.
•  Disconnect the negative battery cable.
•  Disconnect the brake switch connector.
•  Inspect the connector engagement and connection condition and inspect the terminals for damage, deformation, corrosion, or disconnection.
•  Is the connector normal?
Yes
Go to the next step.
No
Repair or replace the connector, then go to Step 7.
2
INSPECT BRAKE SWITCH (NO.1 SIGNAL)
•  Inspect the brake switch (No.1 signal).
•  Is the brake switch (No.1 signal) normal?
Yes
Go to the next step.
No
Replace the brake switch, then go to Step 7.
(See BRAKE PEDAL REMOVAL/INSTALLATION [L.H.D.].)
(See BRAKE PEDAL REMOVAL/INSTALLATION [R.H.D.].)
3
INSPECT BRAKE SWITCH (NO.1 SIGNAL) POWER SUPPLY CIRCUIT FOR OPEN CIRCUIT OR SHORT TO GROUND
•  Verify that the brake switch connector is disconnected.
•  Connect the negative battery cable.
•  Switch the ignition ON (engine off or on).
•  Measure the voltage at brake switch terminal A (vehicle wiring harness side).
•  Is the voltage B+?
Yes
Go to the next step.
No
Inspect the STOP 10 A fuse.
•  If a fuse is burnt out:
―  Repair or replace the wiring harness which is shorted to ground.
―  Replace the burnt out fuse.
•  If a fuse is damaged:
―  Replace the damaged fuse.
•  If the fuse is normal:
―  Repair or replace the wiring harness which has an open circuit.
Go to Step 7.
4
INSPECT START STOP UNIT CONNECTOR CONDITION
•  Disconnect the start stop unit connector.
•  Switch the ignition to off.
•  Disconnect the negative battery cable.
•  Inspect the connector engagement and connection condition and inspect the terminals for damage, deformation, corrosion, or disconnection.
•  Is the connector normal?
Yes
Go to the next step.
No
Repair or replace the connector, then go to Step 7.
5
INSPECT BRAKE SWITCH (NO.1 SIGNAL) CIRCUIT FOR SHORT TO GROUND
•  Verify that the brake switch and start stop unit connectors are disconnected.
•  Inspect for continuity between brake switch terminal D (vehicle wiring harness side) and body ground.
•  Is there continuity?
Yes
Repair or replace the wiring harness which is shorted to ground, then go to Step 7.
No
Go to the next step.
6
INSPECT BRAKE SWITCH (NO.1 SIGNAL) CIRCUIT FOR OPEN CIRCUIT
•  Verify that the brake switch and start stop unit connectors are disconnected.
•  Inspect the wiring harness for an open circuit between brake switch terminal D (vehicle wiring harness side) and start stop unit terminal 1C (vehicle wiring harness side).
•  Is there continuity?
Yes
Go to the next step.
No
Repair or replace the wiring harness which has an open circuit, then go to the next step.
7
VERIFY THAT REPAIRS HAVE BEEN COMPLETED
•  Reconnect all the disconnected connectors.
•  Reconnect the disconnected negative battery cable.
•  Clear DTC for the start stop unit using the M-MDS.
•  With the ignition switched ON (engine off or on), perform the work of depressing the brake pedal for 3 s or more and then releasing it for 5 or more times.
•  Perform the DTC inspection for the start stop unit using the M-MDS.
•  Is DTC C0040:23 displayed?
Yes
Repeat the inspection from Step 1.
•  If the malfunction recurs, replace the start stop unit, then go to the next step.
No
Go to the next step.
8
VERIFY IF OTHER DTCs DISPLAYED
•  Are any other DTCs displayed?
Yes
Repair the malfunctioning part according to the applicable DTC troubleshooting.
(See DTC TABLE [START STOP UNIT].)
No
DTC troubleshooting completed.