ChimeBuzzer - Service Information

A park assist system is an optional factory-installed electronic parking aid. During parking and other similar vehicle maneuvers this system alerts the vehicle operator to obstacles located in the path immediately behind the vehicle which, due to the surrounding rear vehicle structure, might be otherwise difficult to perceive. When an object is detected, the system uses an electromechanical transducer and Light Emitting Diode (LED) indicators within the park assist display unit to provide the vehicle operator with visual and audible indications of the presence and proximity of such objects.

The park assist system includes the following major components, which are described in further detail elsewhere in this service information:

Instrument Cluster (1) - In vehicles equipped with the optional park assist system, the Electronic Vehicle Information Center (EVIC) within the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN) displays textual warnings and error messages and emits audible warnings related to the current operating status of the park assist system and provides an interface that allows the vehicle operator to manually disable or enable the system using the customer programmable features option. Park Assist Display (4) - Vehicles equipped with the park assist system have a park assist display unit mounted in the rear of the headliner just forward of the liftgate opening. The body of the display is concealed above the headliner where it is secured by a retainer on the back of the headliner substrate. Only the narrow, oval-shaped smoked clear lens of the display is visible on the outer surface of the headliner. Park Assist Module (3) - Vehicles equipped with the park assist system include a park assist module

which is secured through integral mounting tabs by push-in type fasteners to the quarter inner panel above and behind the right rear wheel house where it is concealed beneath the quarter inner trim panel. Park Assist Sensors (5) - Vehicles equipped with the park assist system have four ultrasonic park assist sensors that are concealed behind the rear bumper fascia. Each sensor is snapped into an individual molded plastic mounting bracket located at horizontal intervals along the back side of the rear bumper fascia. Park Assist Switch (2) - The optional park assist system can be manually disabled or enabled using either a park assist switch that is integral to the instrument panel switch pod in the instrument panel center stack below the heater and air conditioner controls, or using the settings function found in the menu for the Electronic Vehicle Information Center (EVIC) of vehicles without a park assist switch in the instrument panel switch pod.

Hard wired circuitry connects the various park assist system components to each other through 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 and to the vehicle electrical system 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.

The park assist system components cannot be adjusted or repaired. If any of the park assist system components is damaged or ineffective, that component must be replaced.

The park assist system is active only when the ignition switch is in the ON or START positions, the parking brake is released, the transmission gear selector lever is in the REVERSE position and the vehicle speed is less than 16 kilometers-per-hour (10 miles-per-hour). In vehicles equipped with this option, the system is enabled from the factory as a default. The system can be manually disabled and enabled by the vehicle operator using either the park assist switch integral to the instrument panel switch pod, or by using the settings menu of the Electronic Vehicle Information Center (EVIC) of vehicles not equipped with a park assist switch in the instrument panel switch pod. If the vehicle operator does not want the system active, momentarily depressing the park assist switch OFF button, or selecting the park assist disable setting of the EVIC will disable the system until the switch button is depressed again or the EVIC park assist setting is changed to enabled.

Reasons for disabling the system include trailer towing and off road use. With a trailer attached to the vehicle the audible and visible park assist alerts would be incessant whenever the gear selector lever was in the REVERSE position due to the proximity of the trailer to the rear of the vehicle. Similarly, operating the vehicle off road may cause the park assist alerts to become distracting due to the proximity of large trees or boulders and the extreme rear approach angles that may be encountered while maneuvering on off road trails or terrain.

When the system is disabled, a PARK ASSIST OFF icon and textual message will appear in the EVIC display of the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN) whenever the gear selector lever is in the REVERSE position.

The microprocessor based park assist module is the central component of the park assist system. It supplies voltage to the park assist sensors and the park assist display, receives and analyzes data from the sensors, calculates and communicates the proper display information to the park assist display, performs system diagnostics, and communicates with other electronic modules in the vehicle or with a diagnostic scan tool over the Controller Area Network (CAN) data bus. The module operates on battery voltage received through a fuse in the Totally Integrated Power Module (TIPM), and is grounded through a take out of the body wire harness.

Four ultrasonic park assist sensors in the rear bumper fascia allow the park assist system to locate and identify the proximity of nearby obstacles. These sensors each generate ultrasonic sound pulses when triggered by the park assist module, then signal the module when an echo of the reflected sound pulses is received. The detection distance range from the rear of the vehicle is about 0.3 meters (11.8 inches) to about 2 meters (80 inches), and the detection height range from the ground is about 0.2 meters (7.8 inches) to about 0.8 meters (31 inches). The detection area extends somewhat around both rear sides (corners) of the vehicle.

The park assist display unit provides the vehicle operator with both visible and audible warnings indicating the relative range of a detected object. The display is visible to the vehicle operator over an inboard shoulder when looking rearward while backing the vehicle up, but is not visible in a properly adjusted inside rear view mirror when looking forward. The display contains two sets of eight Light Emitting Diode (LED) indicator units, one set dedicated to each side of the vehicle, and an audible chime tone transducer. The LED units are concealed beneath a smoked oval lens and are not clearly visible when they are not illuminated. When the park assist system is active and no obstacles are detected, the two outermost, amber LED units in the display are illuminated at a reduced intensity to provide visual confirmation that the system is operating.

The display provides a visual indication of a detected object by illuminating one or more LED indicators, amber first followed by red, moving toward the center of the display as the vehicle gets closer to the object. As the vehicle comes to within about 40 centimeters (31 inches) of the object, 1 red LED is illuminated and the display emits a series of short, intermittent, audible beeps. If the audio system is turned ON, the audio output will be muted automatically while the park assist audible warning is being generated. The audible warning changes from intermittent beeps to a continuous tone as the final red indicators are illuminated on 1 or both sides of the display and the vehicle comes to within 30.5 centimeters (12 inches) of a detected object.

When the park assist module monitors a problem in any of the park assist system circuits or components, it stores a fault code or Diagnostic Trouble Code (DTC) in its memory circuit, illuminates all four red LED units in the park assist display, sends an electronic message to the EVIC, and a SERVICE PARK ASSIST SYSTEM textual message is displayed in the EVIC display.

The hard wired circuits between components related to the park assist system 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 system 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 system or the electronic controls and communication related to park assist system operation requires the use of a diagnostic scan tool.

WARNING: To avoid serious or fatal injury on vehicles equipped with airbags, disable the Supplemental Restraint System (SRS) before attempting any steering wheel, steering column, airbag, Occupant Classification System (OCS), seat belt tensioner, impact sensor, or instrument panel component diagnosis or service. Disconnect and isolate the battery negative (ground) cable, then wait two minutes for the system capacitor to discharge before performing further diagnosis or service. This is the only sure way to disable the SRS. Failure to take the proper precautions could result in accidental airbag deployment.

If a SERVICE PARK ASSIST SYSTEM textual message appears in the Electronic Vehicle Information Center (EVIC) display, be certain to confirm the following:

 Be certain that the rear bumper is free of dirt and debris to keep the system operating properly.  Be certain that the parking brake is not applied.

 The presence of jackhammers, large trucks, and other vibrations in the vicinity of the vehicle could impact the performance of the system.

The hard wired circuits between components related to the park assist system 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 system 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 system or the electronic controls and communication related to park assist system operation requires the use of a diagnostic scan tool.

DISPLAY-PARK ASSIST

The park assist display (1) is located in the headliner at the rear of the vehicle, just forward of the upper liftgate opening header. Only the smoked clear plastic display lens (3) is visible on the headliner. The lens prevents the 4 red Light Emitting Diode (LED) units and 12 amber LED units from being clearly visible unless they are illuminated by the electronic circuitry of the display.

The remainder of the display including the mounting provisions and the electrical connection are concealed above the headliner. A molded plastic housing with an integral connector receptacle (2) at one end contains and protects the electronic circuitry of the display, including an audible tone transducer and an electronic communication chip.

A molded plastic retainer (1) with three integral tabs (2) engages three slots integral to the display housing above the lens. The retainer is installed over the display housing above the headliner substrate to engage and securely lock the display into the opening in the headliner. An arrow and the text REAR are molded into an integral installation tab (3) to ensure correct retainer orientation.

The park assist display is serviced only as a complete unit. It cannot be adjusted or repaired. If ineffective or damaged, the entire display unit must be replaced.

The park assist display provides the vehicle operator with visual feedback by illuminating amber or red Light Emitting Diode (LED) units individually or in unison, and audible feedback by energizing an audible tone transducer on the display electronic circuit board to emit either an intermittent or a continuous tone. While the park assist system is active, the number, position and color of the illuminated LED units as well as the audible signal frequency indicate the relative position and distance of obstacles detected at the rear of the vehicle.

The park assist display receives battery current and ground from and is completely controlled by the park assist module. The display also contains an electronic communication chip that allows bi-directional communication to occur with the park assist module over a dedicated serial bus line. The microprocessor in the park assist module completely controls the display outputs, continually monitors the display status, and will store a Diagnostic Trouble Code (DTC) in memory for any monitored fault it detects in the park assist display. The illumination intensity of the LED units is also controlled by the park assist module based upon internal programming and electronic panel lamps dimming messages received over the Controller Area Network (CAN) data bus.

When the ignition switch is turned to the ON position, all 16 of the LED units in the display will illuminate in unison for approximately 1 second as a bulb test. This output will be interrupted if the system is active and senses an obstacle. Following the conclusion of the bulb test, when the system is active but no obstacle is detected, the display will indicate system readiness by illuminating the two outermost amber LED units (1) at a reduced intensity. As an obstacle is detected, the outermost amber LED unit (5) on the side of the vehicle where the obstacle was detected will be illuminated at normal intensity and a single short audible tone (one-half second duration) is sounded. Then additional amber LED units (6) will begin illuminating inward (2 or 4) as the obstacle gets closer until, finally, the two red LED units (7) are illuminated.

When the final red LED unit (3) is illuminated, the obstacle is approximately 40 centimeters (16 inches) from

the rear corner of the vehicle or approximately 50 centimeters (19.7 inches) from the rear bumper face and an intermittent audible tone will be generated. The frequency of the audible tone will increase as the obstacle continues to become closer until the tone is continuous when the obstacle is about 15 centimeters (6 inches) from the rear corner of the vehicle or about 30 centimeters (11.8 inches) from the rear bumper face. Whenever a park assist audible tone is being generated, the park assist module sends electronic messages to the radio over the CAN data bus to mute the audio system. The audible tone will be cancelled after about two seconds if the detected distance to the obstacle remains constant. See the PARK ASSIST DISPLAY OUTPUTS table for additional details.

The hard wired circuits between components related to the park assist display 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 display 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 display or the electronic controls and communication related to park assist display operation requires the use of a diagnostic scan tool.

200 cm (78.7            Single Tone (One-Half Second
1st LED                  -                         Amber
                                         in.)                         Duration)

130 cm (51.2 2nd LED - Amber None in.)

                 -                  115 cm (45.3
3rd LED                                            Amber                None

in.) 100 cm (39.3 4th LED 80 cm (31.5 in.) Amber None in.) 85 cm (33.5 5th LED 65 cm (25.5 in.) Amber None in.) 70 cm (27.6 6th LED 50 cm (20 in.) Amber None in.) 50 cm (19.7 7th LED 40 cm (16 in.) Red 40 cm (16 in.) Intermittent in.) 30 cm (11.8 8th LED 15 cm (6 in.) Red 30 cm (11.8 in.) Continuous in.)

1. Disconnect and isolate the battery negative cable. 2. Remove the trim from the upper liftgate opening. Refer to REMOVAL . 3. Partially remove the quarter trim panel from both upper D-pillars. Refer to REMOVAL . 4. Carefully pull down the rear edge of the headliner (5) from the upper liftgate opening header (2) far enough to access the rear park assist display housing (3) and the display retainer (4). 5. Disconnect the wire harness connector (1) from the connector receptacle on the left end of the display housing. 6. Carefully spread the front and rear edges of the molded plastic retainer far enough to disengage the three retainer tabs from the slots in the display housing, then lift the retainer off of the display housing. 7. Push the right end of the display out through the lower surface of the headliner, then slide the display toward the right side of the vehicle far enough to disengage the connector receptacle from the headliner opening.

1. Carefully position the connector receptacle on the left end of the park assist display housing (3) through the left end of the display opening in the lower surface of the headliner (5). 2. Slide the display toward the left side of the vehicle far enough to engage the right end of the display housing into the right end of the display opening in the headliner. 3. Carefully pull down the rear edge of the headliner from the upper liftgate opening header (2) far enough to access the rear park assist display housing. 4. With the display lens held flush against the lower surface of the headliner, position the molded plastic retainer (4) over the display housing with the installation tab oriented towards the rear of the vehicle. 5. Slide the retainer down over the display housing until it is flash with the headliner substrate and the three tabs of the retainer are engaged in the three slots of the display housing. 6. Reconnect the wire harness connector (1) to the connector receptacle on the left end of the display housing. 7. Reinstall the quarter trim panel onto both upper D-pillars. Refer to INSTALLATION . 8. Reinstall the trim onto the upper liftgate opening. Refer to INSTALLATION . 9. Reconnect the battery negative cable.

MODULE-PARK ASSIST

The Park Assist Module (3) is secured with three push-in plastic fasteners through three mounting tabs (2) integral to the module housing to the right inner quarter panel above the right rear wheel housing. The module is concealed beneath the quarter inner trim panel. Concealed within the molded plastic park assist module housing is a microprocessor and the other electronic circuitry of the module. The module housing is sealed to enclose and protect the internal electronic circuitry. The module software is flash programmable.

Two connector receptacles (1) containing terminal pins are integral to the forward-facing side of the housing. The module is connected to the vehicle electrical system through two dedicated take outs and connectors of the body wire harness.

The park assist module cannot be adjusted or repaired and, if damaged or ineffective, it must be replaced.

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 and to the park assist display located in the headliner just forward of the liftgate opening header. The module then monitors return inputs from each of the sensors and the display 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 and 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 park assist displays over a dedicated serial bus to obtain the proper park assist system visual and audible outputs. The module also broadcasts electronic messages over the CAN data bus to enable the other electronic 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 ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN) over the CAN data bus to control operation of certain park assist system audible warnings and textual messages displayed in the Electronic Vehicle Information Center (EVIC) display of the cluster.

The park assist module receives battery current on a fused ignition switch output (run-start) circuit through a fuse in the Junction Block (JB). The module receives ground through a ground circuit and take out of the body wire harness. 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.

Wire Harness Connectors

1. Disconnect and isolate the battery negative cable. 2. Partially remove the trim from the right quarter inner panel to access the park assist module (2), which is located above and behind the right rear wheel house, forward of the D-pillar. Refer to REMOVAL . 3. Disconnect the two body wire harness connectors (4) from the park assist module connector receptacles. 4. Remove the three plastic push-in fasteners (3) that secure the module to the right quarter inner panel (1). 5. Remove the module from the right quarter inner panel.

Wire Harness Connectors

1. Position the park assist module (2) to the right quarter inner panel (1) behind and above the right rear wheel house, forward of the D-pillar. 2. Secure the module to the right quarter inner panel using three plastic push-in fasteners (3). 3. Reconnect the two body wire harness connectors (4) to the module connector receptacles. 4. Reinstall the trim onto the right quarter inner panel. Refer to INSTALLATION . 5. Reconnect the battery negative cable.

SENSOR-PARK ASSIST

Vehicles equipped with the park assist system have four park assist sensors (1) installed on the rear bumper fascia. Only the membrane (3) of each sensor is visible through a hole in the outer vertical surface of the fascia. The remainder of each sensor including the sensor mounting bracket, the sensor spacer and the sensor wiring connection is concealed behind the fascia. A sensor wire harness behind the fascia connects the sensors to the vehicle electrical system.

Each of the four sensors is identical in construction and is interchangeable. The electronic circuitry and a communication chip for each sensor is enclosed and protected within the molded black plastic sensor housing. The housing includes an integral connector receptacle (4) and two integral latch tabs (2). The sensor membrane extends from the surface of the sensor housing, and is finished to match or contrast with the outer surface of the fascia.

The numbering system for the park assist sensors allows for up to twelve sensors on the vehicle, six front and six rear. The sensors are numbered in a clockwise manner starting at the left front bumper. The left front sensor (if equipped with front park assist) is the number 1 sensor. The numbering continues in a clockwise direction around the vehicle. Since this vehicle uses only four rear sensors, sensor numbers 7 and 12 are omitted, so the left rear sensor is the number 11 sensor.

A resilient O-ring spacer around the circumference of each of the four sensor membranes (2) isolates the membrane from the openings in the fascia (1). Each sensor is snapped into its own dedicated molded plastic mounting bracket. Each mounting bracket is heat-staked to the back side of the rear fascia.

The park assist sensors cannot be adjusted or repaired. If ineffective or damaged they must be replaced. The sensors and the spacers are each available for individual service replacement.

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.

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).

1. Disconnect and isolate the battery negative cable. 2. Remove the rear wheel flare and loosen the bumper fascia on the same side of the vehicle as the park assist sensor requiring service. Refer to REMOVAL . 3. From the back of the fascia (2), disconnect the wire harness connector (4) from the park assist sensor (3) connector receptacle. 4. 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. 5. Disengage the O-ring spacer from around the circumference of the sensor membrane protrusion.

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).

1. Engage the O-ring spacer around the circumference of the sensor membrane protrusion.

NOTE: Production and all service replacement O-ring spacers are tapered. The wide side (base) of the O-ring should be seated against the sensor housing and the narrow side should be oriented toward the outer surface of the sensor membrane and the rear fascia.

2. Align and insert the sensor (3) into the sensor bracket (5) on the back of the rear bumper fascia (2) until the bracket latch features (1) are fully engaged over the top and bottom latch tabs of the sensor. Be certain that the sensor membrane is flush with the outer surface of the fascia.

NOTE: Be certain that each sensor membrane is properly centered in the openings of the rear fascia and that the O-ring spacers are not pinched. Improper centering or pinched O-rings can be detrimental to proper park assist sensor operation.

3. From the back of the fascia, reconnect the wire harness connector (4) to the sensor connector receptacle. 4. Reinstall the rear wheel flare and the bumper fascia on the same side of the vehicle as the park assist sensor that was serviced. Refer to INSTALLATION . 5. Reconnect the battery negative cable.

SWITCH-PARK ASSIST

The park assist switch (2) is integral to the instrument panel switch pod (1), which is secured to the instrument panel center bezel just below the heater and air conditioner controls. The park assist switch push button is clearly identified with a white International Control and Display Symbol graphic for Parking Aid and the text OFF . An amber Light Emitting Diode (LED) unit is illuminated behind a small clear plastic jewel-like lens in the push button to give a visual indication whenever the park assist system has been manually disabled with the ignition switch in the ON or START positions. The switch button also has panel lamps dimmer controlled illumination for night visibility.

All of the circuitry and components of the park assist switch are contained within a molded black plastic instrument panel switch pod housing. A single connector receptacle is integral to the back of the switch pod housing. The switch is connected to the vehicle electrical system through a dedicated take out and connector of the instrument panel wire harness.

The park assist switch cannot be adjusted or repaired and, if the switch is ineffective or damaged, the entire instrument panel switch pod unit must be replaced. Refer to REMOVAL .

The status of the park assist switch is continually monitored by the circuitry within the instrument panel switch pod. The switch pod receives battery voltage at all times on a fused battery feed circuit, and a path to ground at all times through the instrument panel wire harness. The only other inputs to and outputs from the switch pod consist of electronic communication with the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN) over the single wire Local Interface Network (LIN) data bus.

Each time the park assist switch push button is depressed the switch pod circuitry sends an electronic park assist switch status message input to the EMIC over the LIN data bus. The EMIC then sends an electronic park assist switch request message to the park assist module over the Controller Area Network (CAN) data bus. The park assist module responds to each park assist switch request message by toggling the status of the park assist system from enabled to disabled, or from disabled to enabled, then sends an electronic park assist system status message back to the EMIC over the CAN data bus as confirmation.

The EMIC responds to the system status message by sending a message to the switch pod over the LIN data bus to control the park assist switch Light Emitting Diode (LED) unit so that the LED is illuminated with the system disabled and the ignition switch in the ON or START positions, and is extinguished with the system enabled or

with the ignition switch in any position except ON or START.

The hard wired circuits between components related to the park assist switch 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 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 switch or the electronic controls and communication related to park assist switch operation requires the use of a diagnostic scan tool.