OPERATION
The microprocessor in the park assist module contains the park assist system logic circuits. The module 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 Controller Area Network (CAN) data bus. This method of communication is also used for park assist system diagnosis and testing through the 16-way data link connector located on the driver side lower edge of the instrument panel.
The module provides voltage to the four park assist sensors located behind the rear bumper fascia. The module then monitors return inputs from each of the sensors on dedicated hard wired data communication circuits. The sensor inputs allow the module to determine when an obstacle is in the rear path of the vehicle, enables the module to calculate the relative location of the obstacle and whether the distance to that obstacle is increasing or decreasing.
Pre-programmed decision algorithms and calibrations allow the module microprocessor to determine the appropriate park assist system outputs based upon the inputs received from the park assist sensors and electronic messages received from other modules in the vehicle over the CAN data bus. When the programmed conditions are met the module sends electronic messages to the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN) over the CAN data bus to enable the electronic park assist visual displays in the Electronic Vehicle Information Center (EVIC) as well as the audible output features of the park assist system.
The park assist module microprocessor continuously monitors all of the park assist system electrical circuits and components to determine the system readiness. If the module detects a monitored system fault, it sets a Diagnostic Trouble Code (DTC) and sends the appropriate electronic messages to the EMIC over the CAN data bus to control the appropriate textual and audible warnings to indicate the problem to the vehicle operator.
The park assist module receives battery current on a fused ignition switch output (run-start) circuit. The module receives a path to ground at all times through a ground circuit and take out of the body wire harness that is secured to the body sheet metal. These connections allow the module to be operational whenever the ignition switch is in the START or ON positions.
The hard wired circuits between components related to the park assist module 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 park assist module or the electronic controls or communication between modules and other devices that provide some features of the park assist system. The most reliable, efficient and accurate means to diagnose the park assist module or the electronic controls and communication related to park assist module operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.
The park assist sensors are ultrasonic transceivers that are completely controlled by the park assist module. The sensors transmit and receive ultrasonic signals. The sensors each receive battery current and ground in parallel from the module, but are each connected to individual dedicated serial bus communication circuits to the module.
Each sensor membrane is oscillated, then quieted by the module in a pulsing fashion. While the sensor membrane oscillates, it emits an ultrasonic signal. This signal will bounce or echo off of objects in the path of the vehicle. While quieted, each membrane receives the echoes of the ultrasonic signals it and the other sensors have transmitted. The sensors then communicate this echo data over the serial bus lines back to the module. The microprocessor in the module uses the intervals between the ultrasonic transmission and reception data from the sensors to calculate the distance to any obstacles identified by the ultrasonic echoes.
The hard wired circuits between components related to the park assist sensors 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 park assist sensors or the electronic controls or communication between modules and other devices that provide some features of the park assist system. The most reliable, efficient, and accurate means to diagnose the park assist sensors or the electronic controls and communication related to park assist sensor operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.
Scheme 1
Note. The park assist sensors (3) and the sensor spacers (O-rings) are each available for separate service replacement. The sensor brackets (5) are bonded to and integral to the back side of the rear bumper fascia (2).
- Disconnect and isolate the battery negative cable.
- Remove the bumper fascia from the rear of the vehicle. Refer to «FASCIA, REAR, REMOVAL»(ref-489280-S27551809492012072600000) .
- From the back of the fascia (2), disconnect the wire harness connector (4) from the park assist sensor (3) connector receptacle.
- Carefully pry the sensor bracket (5) latch features (1) away from the top and bottom latch tabs of the sensor far enough to disengage the sensor from the bracket.
- Disengage the O-ring spacer from around the circumference of the sensor membrane protrusion.
DESCRIPTION
The park assist system in this vehicle does not have a dedicated park assist switch as in some other models. Instead, the park assist system is manually enabled or disabled through the Electronic Vehicle Information Center (EVIC) integral to the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN) using the EVIC switch pod push buttons located in the left horizontal spoke of the steering wheel. Refer to CENTER, ELECTRONIC VEHICLE INFORMATION, DESCRIPTION and SWITCH, EVIC CONTROL, DESCRIPTION .
The park assist system is manually enabled or disabled by using the push buttons of the Electronic Vehicle Information Center (EVIC) switch pod to navigate to the SETTINGS menu of the EVIC. Use the EVIC switch pod push buttons to scroll down through the menu to the PARK ASSIST menu item, then use the EVIC switch pod push buttons to select whether the park assist system is turned ON or OFF. When the system is turned OFF a PARK ASSIST OFF textual message will appear in the EVIC display each time the transmission gear selector lever is moved to the REVERSE position.