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Additional grounds can typically benefit a vehicle’s electrical system. That is, unless the vehicle is a 2008-to-present Kia® equipped with a battery sensor. If an extra ground cable is installed on the negative battery terminal, it can cause the battery sensor to send incorrect information to the ECM (Engine Control Module), which can generate all sorts of problems.
You can determine if the vehicle has a battery sensor by looking for a connector attached to the negative battery terminal as shown in the image below.
Battery Sensor Function
The battery sensor transmits information about battery voltage and temperature to the ECM. Armed with that information, the ECM controls alternator voltage output and the vehicle’s various electrical control systems. On vehicles equipped with the ISG (Idle Stop and Go) feature, for example, the Idle-stop and auto-start function is dependent on the battery SOC (State Of Charge) and SOH (State Of Health) information received from the battery sensor.
False Diagnostic Trouble Codes
When an extra ground cable is installed on the negative battery terminal, the battery sensor can incorrectly report that the battery is in a discharged state, despite a normal battery condition. The resulting improper operation of various systems and components can set the DTCs (Diagnostic Trouble Codes) shown in the table.
The malfunction indicator lamp may not be illuminated, but numerous trouble codes can be stored. If any of the DTCs mentioned in the table are set, be sure to remove any additional cables attached to the negative battery terminal. Clear the codes and road test the vehicle to confirm the problem has been resolved. Advise the customer not to install additional ground cables at the negative battery terminal.Written by the ALLDATA® CommunitySM Automotive Diagnostic Team, a select group of automotive experts dedicated to helping technicians fix hard-to-repair vehicles more efficiently. Meet the team by visiting http://support.alldata.com/alldata-community.