Ignition Switch: Description and Operation

Ignition Switch Position Run (ISP-R)

The ISP-R provides the PCM with a VBAT input signal from the ignition switch, indicating that the key is in either the ON or START position. When the operator turns the key to the OFF or ACC position, the internal combustion engine immediately ceases to provide power. The PCM coordinates the power down sequence by controlling the VPWR circuit and issuing the correct commands to shut down the electrical system in an orderly fashion. For additional information, REFER to Normal Power Down Sequence in Hybrid Electric Control Software Hybrid Electric Control Software. The PCM maintains power to the TCM through the VPWR until the power down sequence is complete. The TBCM is always powered directly from the low voltage battery which permits wake-up when the vehicle is off.

Ignition Switch Position Run/Start (ISP-RS)

The ISP-RS provides the PCM with a VBAT input signal from the ignition switch, indicating the key is in the START position.