DTC B1318 [BCM]

id0902f5831000

Description

BCM power supply voltage low input

Detection condition

•  BCM power supply voltage from the battery is less than 9 V.

Possible cause

•  PCM DTC is stored.

•  Battery malfunction

•  Generator malfunction

•  BCM connector or terminal malfunction

•  Ignition switch connector or terminal malfunction

•  BCM power supply circuit malfunction

―  Short to ground in wiring harness between battery positive terminal and ignition switch terminal E

―  IGKEY1 30 A fuse malfunction

―  Open circuit in wiring harness between battery positive terminal and ignition switch terminal E

•  Ignition switch malfunction

•  Short to ground in wiring harness between ignition switch terminal C and BCM terminal 4A

•  Open circuit in wiring harness between ignition switch terminal C and BCM terminal 4A

•  BCM power supply circuit malfunction

―  Short to ground in wiring harness between the following terminals:

•  Battery positive terminal—BCM terminal 2A

•  Battery positive terminal—BCM terminal 2B

―  MAIN 150 A fuse malfunction

―  ROOM 15 A fuse malfunction

―  HAZARD 15 A fuse malfunction

―  Open circuit in wiring harness between the following terminals:

•  Battery positive terminal—BCM terminal 2A

•  Battery positive terminal—BCM terminal 2B

•  BCM malfunction

Description	BCM power supply voltage low input
Detection condition	• BCM power supply voltage from the battery is less than 9 V.
Possible cause	• PCM DTC is stored. • Battery malfunction • Generator malfunction • BCM connector or terminal malfunction • Ignition switch connector or terminal malfunction • BCM power supply circuit malfunction ― Short to ground in wiring harness between battery positive terminal and ignition switch terminal E ― IGKEY1 30 A fuse malfunction ― Open circuit in wiring harness between battery positive terminal and ignition switch terminal E • Ignition switch malfunction • Short to ground in wiring harness between ignition switch terminal C and BCM terminal 4A • Open circuit in wiring harness between ignition switch terminal C and BCM terminal 4A • BCM power supply circuit malfunction ― Short to ground in wiring harness between the following terminals: • Battery positive terminal—BCM terminal 2A • Battery positive terminal—BCM terminal 2B ― MAIN 150 A fuse malfunction ― ROOM 15 A fuse malfunction ― HAZARD 15 A fuse malfunction ― Open circuit in wiring harness between the following terminals: • Battery positive terminal—BCM terminal 2A • Battery positive terminal—BCM terminal 2B • BCM malfunction

Diagnostic procedure

Step	Inspection		Action
1	VERIFY PCM DTCs • Retrieve the PCM DTCs using the M-MDS. (See ON-BOARD DIAGNOSTIC TEST [MZI-3.7].) • Are any DTCs displayed?	Yes	Repair or replace the malfunctioning part according to the applicable DTC troubleshooting. (See DTC TABLE [MZI-3.7].)
1		No	Go to the next step.
2	INSPECT BATTERY • Inspect the battery. (See BATTERY INSPECTION [MZI-3.7].) • Is there any malfunction?	Yes	Recharge or replace the battery, then go to Step 12. (See BATTERY RECHARGING [MZI-3.7].) (See BATTERY REMOVAL/INSTALLATION [MZI-3.7].)
2		No	Go to the next step.
3	INSPECT GENERATOR • Inspect the generator. (See GENERATOR INSPECTION [MZI-3.7].) • Is there any malfunction?	Yes	Replace the generator, then go to Step 12. (See GENERATOR REMOVAL/INSTALLATION [MZI-3.7].)
3		No	Go to the next step.
4	INSPECT BCM CONNECTOR • Turn the ignition switch to the OFF position. • Disconnect the negative battery cable. (See BATTERY REMOVAL/INSTALLATION [MZI-3.7].) • Disconnect the BCM connector. • Inspect the connector engagement and connection condition and inspect the terminals for damage, deformation, corrosion, or disconnection. • Is there any malfunction?	Yes	Repair or replace the connector, then go to Step 12.
4		No	Go to the next step.
5	VERIFY IF MALFUNCTION CAUSE IS IGNITION SWITCH CIRCUIT OR OTHER • Verify that the BCM connector is disconnected. • Reconnect the negative battery cable. (See BATTERY REMOVAL/INSTALLATION [MZI-3.7].) • Turn the ignition switch to the ON position. • Measure the voltage at the BCM terminal 4A (wiring harness-side). • Is the voltage B+?	Yes	Go to Step 11.
5		No	Go to the next step.
6	INSPECT IGNITION SWITCH CONNECTOR • Turn the ignition switch to the OFF position. • Disconnect the negative battery cable. (See BATTERY REMOVAL/INSTALLATION [MZI-3.7].) • Disconnect the ignition switch connector. • Inspect the connector engagement and connection condition and inspect the terminals for damage, deformation, corrosion, or disconnection. • Is there any malfunction?	Yes	Repair or replace the connector, then go to Step 12.
6		No	Go to the next step.
7	VERIFY BCM POWER SUPPLY VOLTAGE • Verify that the BCM and ignition switch connectors are disconnected. • Reconnect the negative battery cable. (See BATTERY REMOVAL/INSTALLATION [MZI-3.7].) • Measure the voltage at the ignition switch terminal E (wiring harness-side). • Is the voltage B+?	Yes	Go to the next step.
7		No	Inspect the IGKEY1 30 A fuse. • If a fuse is burnt out: ― Repair or replace the wiring harness which has a short to ground. ― Replace the fuse. • If a fuse is damaged: ― Replace the damaged fuse. • If a fuse is normal: ― Repair or replace the wiring harness which has an open circuit. Go to Step 12.
8	INSPECT IGNITION SWITCH • Inspect the ignition switch. (See IGNITION SWITCH INSPECTION.) • Is there any malfunction?	Yes	Replace the ignition switch, then go to Step 12. (See IGNITION SWITCH REMOVAL/INSTALLATION.)
8		No	Go to the next step.
9	INSPECT FOR SHORT TO GROUND IN IGNITION SWITCH CIRCUIT • Verify that the BCM and ignition switch connectors are disconnected. • Disconnect the negative battery cable. (See BATTERY REMOVAL/INSTALLATION [MZI-3.7].) • Inspect for continuity between ignition switch terminal C (wiring harness-side) and body ground. • Is there continuity?	Yes	Repair or replace the wiring harness which has a short to ground, then go to Step 12.
9		No	Go to the next step.
10	INSPECT FOR OPEN CIRCUIT IN IGNITION SWITCH CIRCUIT • Verify that the BCM and ignition switch connectors are disconnected. • Inspect for continuity between ignition switch terminal C (wiring harness-side) and BCM terminal 4A (wiring harness-side). • Is there continuity?	Yes	Go to the next step.
10		No	Repair or replace the wiring harness which has an open circuit, then go to Step 12.
11	VERIFY BCM POWER SUPPLY VOLTAGE • Verify that the BCM connector is disconnected. • Reconnect the negative battery cable. (See BATTERY REMOVAL/INSTALLATION [MZI-3.7].) • Measure the voltage at the following terminals (wiring harness-side): ― BCM terminal 2A ― BCM terminal 2B • Is the voltage B+?	Yes	Go to the next step.
11		No	Inspect the following fuse: • MAIN 150 A fuse • ROOM 15 A fuse • HAZARD 15 A fuse ― If a fuse is burnt out: • Repair or replace the wiring harness which has a short to ground. • Replace the fuse. ― If a fuse is damaged: • Replace the damaged fuse. ― If a fuse is normal: • Repair or replace the wiring harness which has an open circuit. Go to the next step.
12	VERIFY DTC TROUBLESHOOTING COMPLETED • Make sure to reconnect all disconnected connectors. • Reconnect the negative battery cable. (See BATTERY REMOVAL/INSTALLATION [MZI-3.7].) • Clear the DTC for the BCM using the M-MDS. (See CLEARING DTC [BCM].) • Retrieve the BCM DTCs using the M-MDS. (See DTC INSPECTION [BCM].) • Is the same DTC displayed?	Yes	Repeat the inspection from Step 1. • If the malfunction recurs, replace the BCM. (See BODY CONTROL MODULE (BCM) REMOVAL/INSTALLATION.) Go to the next step.
12		No	Go to the next step.
13	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 [BCM].)
13		No	DTC troubleshooting completed.