S Circuit 4 (WH/BK) (4.0L vehicles built from December 8, 2003)

WARNING: This page is about a different car, the 2004 Mercury Mountaineer and 2004 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.

The S (stator) circuit 4 (WH/BK) (external only on 4.0L vehicles built from December 8, 2003) is used to feed back a voltage signal externally from the generator stator to the regulator. This voltage feedback signal (typically half the battery voltage) is used by the regulator to determine when to open the grounded I circuit 904 (LG/RD) to the PCM. This, in turn, provides a signal over the CAN communication link to the instrument cluster to turn off the charging system warning lamp indicating the charging system is operating properly. The voltage regulator will also use the circuit 904 (LG/RD) as a fault indicator in the event the generator/regulator fails by grounding the I circuit 904 (LG/RD). The PCM will see a voltage drop on the I circuit and will provide a signal to the instrument cluster (through the CAN communication link) to turn on the charging system warning light.