DTC P1794:16 [START STOP UNIT]

id0902p6023700

Description

Start stop unit power supply voltage (terminal 2W) low input
Detection condition
•  Start stop unit power supply circuit voltage (terminal 2W) of less than 6.5 V is detected for 5 s or more.
Fail-safe
Not applicable
Possible cause
•  DTCs are stored in the PCM.
•  DTCs are stored in the DC-DC converter (i-ELOOP).
―  DC-DC converter (i-ELOOP) connector or terminal malfunction
―  DC-DC converter (i-ELOOP) malfunction
•  Battery malfunction
•  Generator malfunction
•  Start stop unit connector or terminal malfunction
•  Start stop unit power supply circuit (terminal 2W) malfunction
―  Without i-ELOOP:
•  Short to ground in wiring harness between MAIN 200 A fuse and start stop unit terminal 2W
•  AT 15 A fuse malfunction
•  MAIN 200 A fuse malfunction
•  Open circuit in wiring harness between battery positive terminal and start stop unit terminal 2W
―  With i-ELOOP:
•  Short to ground in wiring harness between AT 15 A fuse and start stop unit terminal 2W
•  AT 15 A fuse malfunction
•  Open circuit in wiring harness between DC-DC converter (i-ELOOP) terminal 4A and start stop unit terminal 2W
•  Start stop unit malfunction

Diagnostic Procedure

Step

Inspection

Action
1
VERIFY PCM DTCs
•  Retrieve the PCM DTCs using the M-MDS.
•  Are any DTCs displayed?
Yes
Repair or replace the malfunctioning part according to the applicable DTC troubleshooting.
(See DTC TABLE [PCM (SKYACTIV-G 1.5, SKYACTIV-G 2.0)].)
No
Without i-ELOOP:
•  Go to Step 3.
With i-ELOOP:
•  Go to the next step.
2
VERIFY DC-DC CONVERTER (i-ELOOP) DTCs
•  Retrieve the DC-DC converter (i-ELOOP) DTCs using the M-MDS.
•  Are any DTCs displayed?
Yes
Repair or replace the malfunctioning part according to the applicable DTC troubleshooting.
(See DTC TABLE [i-ELOOP].)
No
Go to the next step.
3
INSPECT BATTERY
•  Inspect the battery.
•  Is the battery normal?
Yes
Go to the next step.
No
Recharge or replace the battery, then go to Step 8.
(See BATTERY RECHARGING.)
(See BATTERY REMOVAL/INSTALLATION [SKYACTIV-G 1.5, SKYACTIV-G 2.0].)
4
INSPECT GENERATOR
•  Inspect the generator.
•  Is the generator normal?
Yes
Go to the next step.
No
Replace the generator, then go to Step 8.
(See GENERATOR REMOVAL/INSTALLATION [WITHOUT i-ELOOP (SKYACTIV-G 1.5, SKYACTIV-G 2.0)].)
(See GENERATOR REMOVAL/INSTALLATION [WITH i-ELOOP (SKYACTIV-G 1.5, SKYACTIV-G 2.0)].)
5
INSPECT START STOP UNIT CONNECTOR CONDITION
•  Switch the ignition off.
•  Disconnect the negative battery terminal.
•  Disconnect the start stop unit connector.
•  Inspect the connector engagement and connection condition and inspect the terminals for damage, deformation, corrosion, or disconnection.
•  Is the connector normal?
Yes
Without i-ELOOP:
•  Go to the next step.
With i-ELOOP:
•  Go to Step 7.
No
Repair or replace the connector, then go to Step 8.
6
VERIFY START STOP UNIT POWER SUPPLY VOLTAGE (TERMINAL 2W)
•  Always reconnect all disconnected connectors.
•  Connect the negative battery terminal.
•  Display PID VPWR_B2 using the M-MDS.
•  Is the voltage B+?
Yes
Go to Step 8.
No
Inspect the AT 15 A fuse and MAIN 200 A fuse.
•  Any fuse is blown:
―  Refer to the wiring diagram and verify whether or not there is a common connector between MAIN 200 A fuse and start stop unit terminal 2W.
If there is a common connector:
•  Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for a short to ground.
•  Repair or replace the malfunctioning part.
If there is no common connector:
•  Repair or replace the wiring harness which has a short to ground.
•  Replace the fuse.
•  Any fuse is damaged:
―  Replace the fuse.
•  All fuses are normal:
―  Refer to the wiring diagram and verify whether or not there is a common connector between battery positive terminal and start stop unit terminal 2W.
If there is a common connector:
•  Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for an open circuit.
•  Repair or replace the malfunctioning part.
If there is no common connector:
•  Repair or replace the wiring harness which has an open circuit.
Go to Step 8.
7
VERIFY START STOP UNIT POWER SUPPLY VOLTAGE (TERMINAL 2W)
•  Always reconnect all disconnected connectors.
•  Connect the negative battery terminal.
•  Display PID VPWR_B2 using the M-MDS.
•  Is the voltage B+?
Yes
Go to the next step.
No
Disconnect the service plug.
(See SERVICE PLUG DISCONNECTION/CONNECTION [i-ELOOP].)
Inspect the AT 15 A fuse.
•  If the fuse is blown:
―  Refer to the wiring diagram and verify whether or not there is a common connector between AT 15 A fuse and start stop unit terminal 2W.
If there is a common connector:
•  Determine the malfunctioning location by inspecting the common connector and terminals for corrosion, damage, or disconnection and by inspecting the DC-DC converter (i-ELOOP) terminal 4A-related wiring harness for a short to ground.
•  Repair or replace the malfunctioning part.
If there is no common connector:
•  Repair or replace the wiring harness which is shorted to ground, or the DC-DC converter (i-ELOOP) terminal 4A-related wiring harness.
•  Replace the fuse.
•  If the fuse is damaged:
―  Replace the fuse.
•  If the fuse is normal:
―  Refer to the wiring diagram and verify whether or not there is a common connector between DC-DC converter (i-ELOOP) terminal 4A and start stop unit terminal 2W.
If there is a common connector:
•  Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for an open circuit.
•  Repair or replace the malfunctioning part.
If there is no common connector:
•  Repair or replace the wiring harness which has an open circuit.
Connect the service plug, then go to the next step.
(See SERVICE PLUG DISCONNECTION/CONNECTION [i-ELOOP].)
8
VERIFY THAT REPAIRS HAVE BEEN COMPLETED
•  Always reconnect all disconnected connectors.
•  Connect the negative battery terminal.
•  Clear the DTC for the start stop unit using the M-MDS.
•  Switch the ignition ON (engine off or on) and wait for 5 s or more.
•  Retrieve the start stop unit DTCs using the M-MDS.
•  Is the same Pending DTC present?
Yes
Repeat the inspection from Step 1.
•  If the malfunction recurs, replace the start stop unit.
Go to the next step.
No
Go to the next step.
9
VERIFY IF OTHER DTCs DISPLAYED
•  Are any other DTCs displayed?
Yes
Repair or replace the malfunctioning part according to the applicable DTC troubleshooting.
(See DTC TABLE [START STOP UNIT].)
No
DTC troubleshooting completed.