Diagnostic Overview - Intelligent Battery Sensor (IBS)
The IBS SOC can read low when both Batteries test good. The following items can contribute to, and should be considered when diagnosing a low SOC condition before replacing an IBS or Battery:
- If the vehicle is jump started at the Battery posts bypassing the IBS.
- If the Battery is charged at the Battery posts bypassing the IBS.
- Repeated short trip driving events not allowing enough charge time.
- The IBS accuracy is off and needs to relearn the Battery SOC.
If the SOC is too low a non-MIL DTC (P057F) can set. This DTC does not necessarily mean that there are any faulty components. It may be due to one of the conditions listed above. In many instances, properly charging the Battery or Batteries through the IBS can raise the IBS SOC enough to regain functionality and repair the fault. However, it can sometimes take two or three, 4-hour BUS off sleep cycles for an IBS to learn and update the Battery SOC.
When charging the Battery - The negative clamp should be placed on the negative cable attachment to the IBS, the Jump Post terminal if equipped, or a good chassis ground, NOT the Pole clamp at the negative Battery post. Without proper clamp placement, the IBS data will not update and possibly cause a misdiagnosis.
On vehicles that are equipped with a dual Battery Stop/Start system the IBS is connected to the Main/Cranking Battery. Since the two Batteries are connected to each other except for a brief disconnection during cranking, the Battery SOC reported by the IBS is reporting the average SOC of the two Batteries. It is possible for one of the Batteries to be fully charged and the other Battery discharged causing the overall SOC to be low. Both Batteries should be checked for proper charge and functionality before checking for an issue with the IBS.
If charging does not raise the SOC the IBS can be forced into a learning curve by completely disconnecting the IBS from the Battery and harness connector for 20 seconds. The IBS Battery feed, LIN Bus and ground circuits should be checked for opens or shorts before reconnecting the IBS. The IBS will default to approximately 80% SOC when reconnected. However, the IBS accuracy is determined to be low until the IBS is allowed to learn during an ignition off sleep cycle of between one and four hours. Some features will be disabled until the IBS SOC is updated.