Technical Case by Rob Miller

Situation: 

The battery charge warning lamp may be displayed in the Instrument Cluster with Diagnostic Trouble Code (DTC) B11DB-87 stored in the Body Control Module (BCM).

Cause:

This may be caused by a blown Battery Monitoring System (BMS) fused harness.

Symptoms

• B11DB-87 Battery Monitoring Module A - Missing message
• Battery monitoring system circuit open circuit, high resistance
• Battery monitoring system internal failure
• Auxiliary junction box internal failure

Initial Checks

A pin-point test is available to help diagnose DTC B11DB-87. For additional information, refer to:
Battery (414-01 Battery, Mounting and Cables, Diagnosis and Testing).

1. Check the integrity of the battery monitoring system connectors. Repair as required.
2. Check the battery monitoring system control module circuit between the BMS and the auxiliary junction box. Repair the wiring harness as necessary.
   Check the battery monitoring system circuit for open circuit, high resistance between the BMS and the auxiliary battery positive terminal. Repair as required.
3. Clear the Diagnostic Trouble Code(s) and retest. Then perform routine - Power Supply Service Mode Diagnostic
4. If the fault persists, check and install a new battery monitoring system control module as required.
5. Check the LIN circuit between the Battery Monitoring System Module and the Gateway module.
6. Should also check LIN control unit power and ground circuits.

Circuit
C1DC05A: Module-Battery monitoring system

C1DC05A-1 Green-White LIN circuit to the Central Junction Box
C1DC05A-2 Blue-Orange inline fuse fed from the positive terminal of the battery, this gives the BMS a true battery voltage direct from the battery and can monitor it sending out a signal on the LIN wire
to the GWM gateway module this then transmits a signal to the generator via a private LIN between the GWM and the Generator.

The BMS is ground through its fixings to the negative post of the battery then off to a chassis earth point.

Further checks:

Ensure that the power supply from the battery is present on the Blue-Orange wire.

• No, suspect inline fuse has blown and will require a replacement sub-harness

(Contact dealer or supplier for VIN specific part number image above)

• Yes, carry on with next check

Ground Supply is present and good, if not clean BMS mating face and body/chassis earth point.

LIN Circuit

This is on the Green-White wire usually 1-volt below battery voltage.

This goes from the BMS to the Central Junction Box CJB as previously described.

Measure the voltage at the BMS connector C1DC05A-1 Green-White and then compare this reading to the one at the GWM.

The GWM connector is known as C1Y122: Module-Gateway Location Behind passenger side of Instrument panel on the Left hand inner lower A post red connector with 20 cavities.

Remove out locking cover taking note of insert position relative to the GWM and refit it.

Locate the Green -White wire at C1Y122-3 Measure the voltage here does it match that of the BMS connector?

• YES, suspect BMS unit faulty,
• NO, resistance pulling down the voltage. Disconnect connectors and load test it.

No voltage present, check continuity and load test the wire if open circuit suspect a break in the wire examples of such break as below in the attached images.

In this instance they had to remove scuttle panel and the abs module bracket, lift abs module up out the way!

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