Operation - Pcm Ground
WARNING: This page is about a different car, the 2006 Dodge Viper. However, it is still accessible from the selected car via links, so may be relevant.
Ground is provided through multiple pins of the PCM connector. Depending on the vehicle there may be as many as two different ground pins. There are power grounds and sensor grounds.
The power grounds are used to control the ground side relays, solenoids, ignition coil or injectors. The signal ground is used for any input that uses sensor return for ground.
The PCM case is shielded to prevent RFI and EMI. The PCM case is grounded.
Internally all grounds are connected together, however there is noise suppression on the sensor ground.