Multiplex Communication Network

Multiplex Communication Network Components:

The multiplex communication network provides:
- the ability for module-to-module communication by sharing required inputs and outputs instead of each component having an input or output wired directly to or from each affected module.
- a common link for communication to an off-board tester through the Data Link Connector (DLC) located under the instrument panel to the right of the steering column.

Three micro-processor based subsystems are included on this network:
- powertrain control
- passive anti-theft
- climate control

The communication bus between these subsystems and the Data Link Connector (DLC) consists of an unshielded twisted pair of wires:
- circuit 914 (T/O) Bus+
- circuit 915 (PK/LB) Bus-

FAULT TOLERANCE
The multiplex communication network will remain operational in the event:
- one circuit is severed.
- one circuit is shorted to ground.
- one circuit is shorted to battery positive voltage (B+).
- a termination resistor is lost within a module.
- one or more modules fail internally.

Any of these conditions will be detected and reported to the off-board tester during diagnostics in the form of a Diagnostic Trouble Code (DTC).

PURPOSE
The information is designed to diagnose any multiplex communication network concerns. These concerns may:
- affect normal functional operations of the vehicle.
- be directly related to customer concerns.
- be undetectable except during diagnostics.

To properly diagnose a network concern, follow the diagnostic procedure in the order presented.

MODULE IDENTIFICATION
Modules included on this multiplex communication network include:

Powertrain Control Module:
- located in the engine compartment on the RH side of the dash panel.
- a failure of the multiplex communication network to the Powertrain Control Module (PCM) may result in a no start condition.
- if communication to the PCM fails during diagnosis, refer to Testing and Inspection procedures.

Passive Anti-Theft System (PATS) Module:
- located behind the integrated control panel.
- works in conjunction with Powertrain Control Module (PCM) to enable or disable engine start function.
- failure of the Passive Anti-Theft System (PATS) or communication to the module may result in a no start condition.
- if communication to the PATS module fails during diagnostics, refer to Antitheft and Alarm Systems to diagnose PATS concerns.

Remote Climate Control (RCC) Module:
- located on the A/C evaporator case on the passenger side of the vehicle.
- loss of communication to Powertrain Control Module (PCM) may result in degraded automatic temperature control.
- if communication to the Remote Climate Control (RCC) module is lost, refer to Electronic Climate Control diagnostic procedures to diagnose RCC module concerns.