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. Refer to «MODULE, ANTI-LOCK BRAKE SYSTEM, DESCRIPTION»(ref-476533-S24941619182012060400000) .
- 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. Refer to «SWITCH, STOP LAMP, DESCRIPTION»(ref-476510-S05575931862012060400000) .
- ElectroMechanical Instrument Cluster - A CRUISE indicator is located in the fixed segment display of 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. Refer to «DESCRIPTION»(ref-476514-S28387971942012060400000) .
- Powertrain Control Module - The Powertrain Control Module (PCM) located in the left front corner of 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. Refer to appropriate Electrical Diagnostic article. .
- 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. Refer to «SENSOR, WHEEL SPEED, FRONT, DESCRIPTION»(ref-476496-S08327803382012060400000) .
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. Refer to COMMUNICATION, DESCRIPTION .
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 pod on the face of the right horizontal spoke of 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.
Scheme 1
The speed control switch pod (1) is located in the right spoke of the steering wheel spoke bezel. This switch has four push buttons and is used on all vehicles equipped with the optional speed control (also known as cruise control) system. The only visible components of the switch pod are the switch push buttons and a decorative bezel around the push buttons, which stands slightly proud of the steering wheel spoke bezel. The remainder of the switch pod including its mounting provisions and its electrical connection are concealed beneath the spoke bezel.
The switch pod housing and push buttons are constructed of molded plastic. Each of the push buttons has white International Control and Display Symbol graphics or text applied to it, which clearly identify the function of each push button. The switch pod is secured through three integral mounting tabs (2) to mounting bosses on the back of the spoke bezel by three screws. A connector receptacle (3) integral to the inboard end of the switch pod housing connects the speed control switch and the Local Interface Network (LIN) slave node circuitry integral to the switch pod to the vehicle electrical system through a dedicated take out and connector of the steering wheel wire harness.
The speed control switch pod cannot be adjusted or repaired. If any function of the switch or the LIN slave node is ineffective or damaged, the entire switch pod unit must be replaced.
The speed control switch pod is a resistor multiplexed unit that provides hard wired inputs to the Powertrain Control Module (PCM) microprocessor. The speed control switch pod also contains the circuitry of a Local Interface Network (LIN) slave node, which provides source current for and communicates the switch or sensor states of the Electronic Vehicle Information Center (EVIC) switches, the remote radio switches and the horn switch over the LIN data bus to the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN), which is the LIN master node.
The speed control switch pod for vehicles equipped with the electronic speed control system contains four switch push buttons whose functions are
- On/Off - This switch button enables or disables the speed control system and clears any previous speed control set speed from system memory.
- Resume / + - This switch button restores the vehicle to a previously stored set speed or accelerates the vehicle from an already attained set speed.
- Cancel - This switch button cancels the current speed control event, but does not turn the system OFF or clear the currently stored set speed.
- Set / - - This switch button sets the current vehicle speed as the stored set speed or decelerates (coasts) the vehicle to a speed that is slower than the already attained set speed.
The EMIC LIN master node provides a clean ground and fused B(+) current for all of the switches and sensors on the rotating steering wheel through the LIN slave node circuitry of the speed control switch pod as well as for the Light Emitting Diode (LED) back lighting of both the speed control and the EVIC switch pods. The PCM continually monitors all of the hard wired speed control switch circuits, while the EMIC continually monitors the LIN bus data. The PCM will set a Diagnostic Trouble Code (DTC) for any problem it detects in the speed control switch circuits, and the EMIC will store a Signal Not Available (SNA) code for any LIN bus input errors. The PCM and EMIC also communicate with other electronic modules over the Controller Area Network (CAN) data bus. Therefore, any PCM or EMIC DTC information can be retrieved using a diagnostic scan tool connected to the Data Link Connector (DLC).
The analog resistor multiplexed circuits of the speed control switch pod as well as the hard wired circuits between the switch pod and the PCM or EMIC may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, details of wire harness routing and retention, connector pin-out information and location views for the various wire harness connectors, splices and grounds.
However, conventional diagnostic methods will not prove conclusive in the diagnosis of the LIN slave or master nodes, the PCM, the EMIC or the electronic controls and communication between modules and other devices that provide some features of the speed control system. The most reliable, efficient, and accurate means to diagnose the speed control switch pod, the LIN slave or master nodes, the PCM, the EMIC 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.