DTC P1794:16 [START STOP UNIT]

id0902p6023700

System malfunction location

Start stop unit power supply voltage (+B2) low input

Detection condition

•  Start stop unit power supply circuit (+B2) voltage of less than 6.5 V is detected for 5 s or more.

Fail-safe

—

Possible cause

•  DTCs are stored in the PCM.

•  Battery malfunction

•  Generator malfunction

•  Start stop unit connector or terminal malfunction

•  Start stop unit power supply circuit (+B2) malfunction

―  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 battery positive terminal and start stop unit terminal 2W

•  Start stop unit malfunction

System malfunction location	Start stop unit power supply voltage (+B2) low input
Detection condition	• Start stop unit power supply circuit (+B2) voltage of less than 6.5 V is detected for 5 s or more.
Fail-safe	—
Possible cause	• DTCs are stored in the PCM. • Battery malfunction • Generator malfunction • Start stop unit connector or terminal malfunction • Start stop unit power supply circuit (+B2) malfunction ― 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 battery positive terminal and start stop unit terminal 2W • Start stop unit malfunction

Diagnostic Procedure

Step	Inspection		Action
1	VERIFY PCM DTCs • Perform the DTC inspection for the PCM using the M-MDS. (See ON-BOARD DIAGNOSTIC TEST [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) (See ON-BOARD DIAGNOSTIC TEST [SKYACTIV-D 2.2].) • Is the DTC displayed?	Yes	Repair the malfunctioning part according to the applicable DTC troubleshooting. (See DTC TABLE [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) (See DTC TABLE [SKYACTIV-D 2.2].)
1		No	Go to the next step.
2	INSPECT BATTERY • Inspect the battery. (See BATTERY INSPECTION [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) (See BATTERY INSPECTION [SKYACTIV-G 2.0, SKYACTIV-G 2.5 (WITHOUT i-stop)].) (See BATTERY INSPECTION [SKYACTIV-D 2.2].) • Is the battery normal?	Yes	Go to the next step.
2		No	Recharge or replace the battery, then go to Step 6. (See BATTERY RECHARGING [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) (See BATTERY RECHARGING [SKYACTIV-G 2.0, SKYACTIV-G 2.5 (WITHOUT i-stop)].) (See BATTERY RECHARGING [SKYACTIV-D 2.2].) (See BATTERY REMOVAL/INSTALLATION [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) (See BATTERY REMOVAL/INSTALLATION [SKYACTIV-D 2.2].)
3	INSPECT GENERATOR • Inspect the generator. (See GENERATOR INSPECTION [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) (See GENERATOR INSPECTION [SKYACTIV-D 2.2].) • Is the generator normal?	Yes	Go to the next step.
3		No	Replace the generator, then go to Step 6. (See GENERATOR REMOVAL/INSTALLATION [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) (See GENERATOR REMOVAL/INSTALLATION [SKYACTIV-D 2.2].)
4	INSPECT START STOP UNIT CONNECTOR CONDITION • Switch the ignition to off. • Disconnect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION [SKYACTIV-G 2.0, SKYACTIV-G 2.5 (WITHOUT i-stop)].) (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION [SKYACTIV-D 2.2].) • 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	Go to the next step.
4		No	Repair or replace the connector, then go to Step 6.
5	INSPECT START STOP UNIT POWER SUPPLY CIRCUIT (+B2) • Reconnect all the disconnected connectors. • Connect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION [SKYACTIV-G 2.0, SKYACTIV-G 2.5 (WITHOUT i-stop)].) (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION [SKYACTIV-D 2.2].) • Display PID VPWR_B2 using the M-MDS. (See PID/DATA MONITOR INSPECTION [START STOP UNIT].) • Is the voltage B+?	Yes	Go to the next step.
5		No	Inspect the AT 15 A fuse. • If a fuse is burnt out: ― Repair or replace the wiring harness which is shorted to ground. ― Replace the fuse. • If a fuse is damaged: ― Replace the fuse. • If the fuse is normal: ― Repair or replace the wiring harness which has an open circuit. Go to the next step.
6	VERIFY THAT REPAIRS HAVE BEEN COMPLETED • Reconnect all the disconnected connectors. • Reconnect the disconnected negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION [SKYACTIV-G 2.0, SKYACTIV-G 2.5].) (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION [SKYACTIV-G 2.0, SKYACTIV-G 2.5 (WITHOUT i-stop)].) (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION [SKYACTIV-D 2.2].) • Clear DTC for the start stop unit using the M-MDS. (See CLEARING DTC [START STOP UNIT].) • Switch the ignition ON (engine off or on) and wait for 5 s or more. • Perform the DTC inspection for the start stop unit using the M-MDS. (See DTC INSPECTION [START STOP UNIT].) • Is DTC P1794:16 displayed?	Yes	Repeat the inspection from Step 1. • If the malfunction recurs, replace the start stop unit, then go to the next step. (See START STOP UNIT REMOVAL/INSTALLATION.)
6		No	Go to the next step.
7	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].)
7		No	DTC troubleshooting completed.