Body Control Systems

Smart Junction Box (SJB)

Pinpoint Test C: DTC B1318

Refer to Wiring Diagram Set 13, Power Distribution/SJB for schematic and connector information. [1][2]Diagrams By Number

Normal Operation

- DTC B1318 (Battery Voltage Low)- a continuous and on-demand DTC that sets when the SJB (Smart Junction Box) detects battery voltage below 10 volts.

This pinpoint test is intended to diagnose the following:

- Wiring, terminals or connectors

- High circuit resistance

- SJB (Smart Junction Box)

PINPOINT TEST C : DTC B1318

NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.

NOTE: Failure to disconnect the battery when instructed will result in false resistance readings.

C1 RECHECK THE SJB (Smart Junction Box) DTCs

- Ignition ON.

- Enter the following diagnostic mode on the scan tool: SJB (Smart Junction Box) Self-Test.

- Clear the DTCs. Repeat the SJB (Smart Junction Box) self-test.

Is DTC B1318 still present?

Yes
GO to C2.

No
The system is operating normally at this time. The DTC may have been set previously during battery charging or while jump starting the vehicle.

C2 CHECK FOR CHARGING SYSTEM DTCs IN THE PCM

- Enter the following diagnostic mode on the scan tool: PCM Self-Test.

- Retrieve the continuous memory DTCs from the PCM.

Is DTC P0620, P0625, P0626 or P065B set in the PCM?

Yes
REFER to Charging System.

No
GO to C3.

C3 CHECK THE BATTERY CONDITION AND STATE OF CHARGE

- Ignition OFF.

- Check the battery condition and verify the battery is fully charged.

Is the battery OK and fully charged?

Yes
GO to C4.

No
REFER to Charging System.

C4 CHECK THE SJB (Smart Junction Box) VOLTAGE SUPPLY

- Measure and record the voltage at the battery.

- Disconnect: SJB (Smart Junction Box) C2280G.

- Ignition ON.

- Measure the voltage between the SJB (Smart Junction Box) C2280G-1, circuit SDC02 (RD), harness side and ground.





Is the voltage within 0.2 volt of the recorded battery voltage?

Yes
GO to C5.

No
REPAIR the circuit for high resistance. CLEAR the DTC. REPEAT the self-test.

C5 CHECK THE SJB (Smart Junction Box) GROUND CIRCUIT

- Ignition OFF.

- Disconnect: Negative Battery Cable.

- Disconnect: SJB (Smart Junction Box) C2280D.

- Measure the resistance between the SJB (Smart Junction Box) C2280D-8, circuit GD126 (BK/WH), harness side and ground; and between the SJB (Smart Junction Box) C2280D-12, circuit GD126 (BK/WH), harness side and ground.





Are the resistances less than 5 ohms?

Yes
CONNECT the negative battery cable. GO to C6.

No
REPAIR the circuit for high resistance. CONNECT the negative battery cable. TEST the system for normal operation.

C6 CHECK FOR CORRECT SJB (Smart Junction Box) OPERATION

- Disconnect the SJB (Smart Junction Box) connectors.

- Check for:
- corrosion

- damaged pins

- pushed-out pins


- Connect the SJB (Smart Junction Box) connectors and make sure they seat correctly.

- Operate the system and verify the concern is still present.

Is the concern still present?

Yes
INSTALL a new SJB (Smart Junction Box). REFER to Smart Junction Box (SJB) . TEST the system for normal operation.

No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.