Pinpoint Test AL: DTC B1318 (Audio Rear Control Unit (RCU) Module)

Information and Entertainment System

Pinpoint Test AL: DTC B1318 (Audio Rear Control Unit (RCU) Module)

Normal Operation

- DTC B1318 (Battery Voltage Low)- set by the audio Rear Control Unit (RCU) module when the supply voltage falls below 10 volts for at least 10 seconds during normal operation.

This pinpoint test is intended to diagnose the following:

- Wiring, terminals or connectors

- High circuit resistance

- Audio RCU (Rear Control Unit) module

PINPOINT TEST AL : DTC B1318 (AUDIO RCU (Rear Control Unit) MODULE)

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.

AL1 RECHECK THE ACM (Audio Front Control Module) DTCs

- Ignition ON.

- Clear the audio RCU (Rear Control Unit) module DTCs.

- Wait at least 15 seconds.

- Repeat the audio RCU (Rear Control Unit) module self-test.

Is DTC B1318 or DTC U3003:16 still present?

Yes
GO to AL2.

No
The system is operating correctly at this time. The DTC may have been set due to a previous low battery voltage condition.

AL2 CHECK FOR CHARGING SYSTEM DTCs IN THE PCM

- Retrieve the continuous DTCs from all modules.

Is DTC P0620, P0622, P0625, or P065B set in the PCM?

Yes
REFER to Charging System.

No
GO to AL3.

AL3 CHECK THE BATTERY CONDITION AND STATE OF CHARGE

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

Is the battery OK and fully charged?

Yes
GO to AL4.

No
REFER to Battery.

AL4 CHECK THE AUDIO RCU (Rear Control Unit) MODULE VOLTAGE SUPPLY

- Ignition OFF.

- Measure and record the voltage at the battery.

- Disconnect: Audio RCU (Rear Control Unit) Module C3077.

- Ignition ON.

- Measure the voltage between the audio RCU (Rear Control Unit) module C3077-16, circuit SBP03 (BU/RD), harness side and ground.





Is the voltage at the ACM (Audio Front Control Module) within 0.2 volt of the recorded battery voltage?

Yes
GO to AL5.

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

AL5 CHECK THE ACM (Audio Front Control Module) GROUND CIRCUIT FOR CONTINUITY

- Ignition OFF.

- Disconnect: Negative Battery Cable.

- Measure the resistance between the audio RCU (Rear Control Unit) module C3077-1, circuit GD114 (BK/BU), harness side and ground.





Is the resistance less than 5 ohms?

Yes
GO to AL6.

No
REPAIR the circuit for high resistance. CLEAR any DTCs present. REPEAT the self-test.

AL6 CHECK FOR CORRECT AUDIO RCU (Rear Control Unit) MODULE OPERATION

- Ignition OFF.

- Connect: Negative Battery Cable.

- Disconnect the audio RCU (Rear Control Unit) module connector.

- Check for:
- corrosion

- damaged pins

- pushed-out pins


- Connect the audio RCU (Rear Control Unit) module connector and make sure it seats correctly.

- Operate the system and determine if the concern is still present.

Is the concern still present?

Yes
INSTALL a new audio RCU (Rear Control Unit) module. REFER to Audio Rear Control Unit (RCU) Module . 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. CLEAR the DTCs.