Section 41 (Electronic Control Modules): Communication: Operation

WARNING: This page is about a different car, the 2004 Dodge Dakota and 2003 Dodge Dakota. However, it is still accessible from the selected car via links, so may be relevant.

Data exchange between modules is achieved by serial transmission of encoded data over a single wire broadcast network. The PCI data bus messages are carried over the bus in the form of Variable Pulse Width Modulated (VPWM) signals. The PCI data bus speed is an average 10.4 Kilo-bits per second (Kbps).

The voltage network used to transmit messages requires biasing and termination. Each module on the PCI data bus system provides its own biasing and termination. Each module (also referred to as a node) terminates the bus through a terminating resistor and a terminating capacitor. The Powertrain Control Module (PCM) is the only dominant node for the PCI data bus system.

The PCI bus uses low and high voltage levels to generate signals. The voltage on the buss varies between zero and seven and one-half volts. The low and high voltage levels are generated by means of variable-pulse width modulation to form signals of varying length.

When a module is transmitting on the bus, it is reading the bus at the same time to ensure message integrity.

Each module is capable of transmitting and receiving data simultaneously.

The PCI data bus can be monitored using the DRBIII(R) scan tool. It is possible for the bus to pass all DRBIII(R) tests and still be faulty if the voltage parameters are all within the specified range and false messages are being sent.