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LESSON 5: DIAGNOSIS 5-45 Battery Diagnostic System (BDS) Battery Module and Diagnosing a battery module or sense lead fault can be of critical importance when a vehicle is brought in for service. • It is important to note that a single bad module or single sense lead will not usually illuminate any of the warning lights in the instrument cluster. • However, if signals from five or more modules are lost, an emergency power off (EPO) condition will occur, which will result in a power limit light illumination, no charging, and a vehicle shutdown. Because all the batteries in the battery pack are wired in series, a bad module may cause a significant loss of range. Because of this series arrangement, one weak module limits the energy output of the whole pack. However, sometimes the symptoms may not be very apparent. Symptoms of module failure can vary depending on the severity of the failure. • For example, if a module’s capacity is only slightly lower than the other modules in the pack, the vehicle’s range may only be decreased slightly. • If the customer never runs the battery pack below 40 or 50% state of charge (SOC), they may not notice any decrease in vehicle range. • However, DTC C1671 (BATTERY VOLTAGE OUT OF RANGE) will be stored in the BCM’s memory. If an individual module’s capacity is significantly lower than the other modules of the battery pack, its failure can cause a significant decrease in vehicle range that will be readily apparent to most customers. • It should be noted that weak battery modules tend to occur one at a time. • A single battery sense lead failure will usually have no symptoms at all. As with a bad module, no warning light in the instrument cluster will illuminate, and the only way you may become aware of the failure is that a DTC 1671 will be stored in the BCM’s memory. • The rule for a sense lead failure is that a bad sense lead will cause a fault to be indicated in two modules. |