DTC B1318 [BCM]

id0902f5831000

Description | BCM power supply voltage low input
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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
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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].)
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].)
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].)
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.
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.
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.
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.
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.)
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.
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.
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.
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.
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].)
No | DTC troubleshooting completed.