Speed Control System

Speed Control System

Description

An electronic speed control (also known as cruise control) system is available factory-installed equipment on this vehicle. The electronic speed control system includes the following major components, which are described in further detail elsewhere in this service information:

• Antilock Brake Module - An Antilock Brake Module (ABM) (also known as Controller Antilock Brake/CAB or the Electronic Stability Control/ESC module) is located on the antilock brake Hydraulic Control Unit (HCU) in the engine compartment.

• Brake Lamp Switch - The brake (also known as stop) lamp switch is located on the brake pedal support bracket under the driver side of the instrument panel.

• ElectroMechanical Instrument Cluster - A CRUISE indicator is located in the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN) that provides an indication to the vehicle operator when the speed control system is turned ON..

• Powertrain Control Module - The Powertrain Control Module (PCM) located in the engine compartment contains the software and hardware that monitors all of the speed control system inputs and controls all of the speed control system outputs.

• Speed Control Switches - A speed control switch pod containing four momentary switch push buttons is located in the right horizontal spoke of the steering wheel.

• Wheel Speed Sensors - A wheel speed sensor is located on the knuckle of each front and rear wheel.

The ABM, the EMIC and the PCM each contain a microprocessor and programming that allow them to communicate with each other using the Controller Area Network (CAN) data bus. This method of communication is used by the PCM for control of the CRUISE indicator in the EMIC.

Hard wired circuitry connects the conventional electronic speed control system components to the electrical system of the vehicle. These hard wired circuits are integral to several wire harnesses, which are routed throughout the vehicle and retained by many different methods. These circuits may be connected to each other, to the vehicle electrical system and to the speed control system components through the use of a combination of soldered splices, splice block connectors, and many different types of wire harness terminal connectors and insulators. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, further details on wire harness routing and retention, as well as pin-out and location views for the various wire harness connectors, splices and grounds.

Operation

The vehicle operator controls all speed control system features through the speed control switch on the steering wheel. When a push button of the switch pod is depressed it provides a hard wired resistor multiplexed analog input to the Powertrain Control Module (PCM).

The PCM reads the speed control switch input, along with other hard wired and electronic message inputs received from other electronic modules in the vehicle over the Controller Area Network (CAN) data bus. The PCM software continually monitors these inputs as well as electronic vehicle distance message inputs from the Antilock Brake Module (ABM) (also known as the Controller Antilock Brake/CAB or the Electronic Stability Control/ESC module) and numerous hard wired inputs including the brake (or stop) lamp switch, then provides the appropriate electronic message and hard wired outputs to invoke the requested and programmed electronic speed control features.

The PCM microprocessor continuously monitors all of the speed control system electrical circuits to determine the system readiness. If the PCM detects a monitored system fault, it sets and stores a Diagnostic Trouble Code (DTC). The PCM uses On-Board Diagnostics (OBD) and can communicate with other electronic modules in the vehicle as well as with the diagnostic scan tool using the CAN data bus. This method of communication is used for control of the Cruise indicator and the Malfunction Indicator Lamp (MIL) (also known as the Check Engine lamp) in the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN) and for system diagnosis and testing through the 16-way Data Link Connector (DLC) located on the driver side lower edge of the instrument panel.

The hard wired inputs and outputs for the PCM may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the PCM or the electronic controls or communication between other modules and devices that provide features of the speed control system. The most reliable, efficient, and accurate means to diagnose the PCM or the electronic controls and communication related to speed control system operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.