Principles of Operation: Notes

WARNING: This page is about a different car, the 2010 Mercury Mariner and 2010 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: The Smart Junction Box (SJB) is also known as the Generic Electronic Module (GEM).

The Parking Aid Module (PAM) communicates with several modules over the High Speed Controller Area Network (HS-CAN), via network messaging, in order to control the functions of the active park assist system.

When the active park assist switch is pressed, a ground signal input is sent to the PAM enabling the active park assist system. An LED, which is integral to the active park assist switch, illuminates.

The PAM proves-out the indicator, located in the active park assist switch, by illuminating the indicator for 3 seconds after each ignition cycle. If the PAM detects a failure, it illuminates the indicator for as long as the failure condition exists and the ignition switch is in the RUN position.

The PAM sends an HS-CAN message to the Instrument Cluster (IC) and the IC message center displays the message "ACTIVE PARK SEARCHING". The IC gateways the turn signal input from the multifunction switch to the PAM via a network message to determine which side of the vehicle the operator is parking. The arrow symbol "□□ >>" in the message center indicates which side of the vehicle is being parked. If the turn signal is not selected, the active park assist system defaults to searching and parking on the passenger side of the vehicle.

The 2 long range ultrasonic active park assist sensors that are located in the left and right side of the front bumper cover are continuously sending out ultrasonic signals to detect an available parking space and communicating the information back to the PAM . This occurs if the vehicle is moving regardless if the operator has pressed the active park assist switch. The active park assist sensor distance detection range is approximately 390 cm (154 in), projecting outward from the side of the vehicle. For information on range detection, refer to AZIMUTH SYSTEM CHECK .

Each available parking space is scanned on both sides of the vehicle as the operator drives by. The active park assist system only offers the available spaces that are on the active side of the vehicle. The system measures the available parking spaces and its surroundings as the operator drives by to determine if the vehicle can be maneuvered into the available parking space. This is determined from the input signals sent to the PAM from the active park assist sensors. The minimum length that the active park assist system offers is approximately 1.3 times the length of the vehicle.

Once a parking space is located and the system has been activated by the operator pressing the active park assist switch, the PAM sends an HS-CAN message to the IC and the message center displays "SPACE FOUND PULL FORWARD" followed by an audible chime from the IC . The operator pulls the vehicle forward and the IC message center displays the message "SPACE FOUND STOP". Once the operator has stopped the vehicle, the IC message center displays the message "REMOVE HANDS PUT IN REVERSE". The active park assist system takes control of the steering after the transaxle is placed in REVERSE (R) and the Power Steering Control Module (PSCM) does not detect the operator input torque on the steering wheel.

After the PAM has received these inputs, it sends steering command messages to the PSCM over the HS-CAN . The PSCM is part of the Electronic Power Assist Steering (EPAS) system steering gear and is used to control the steering portion of the active park assist system and monitors the operator input torque to the steering wheel. For information on the EPAS system, refer to STEERING SYSTEM .

The PSCM and the PAM utilize steering angle inputs that are transmitted by the steering wheel position sensor (integral to the EPAS system) for steering wheel position. The vehicle wheel roll count, wheel direction and wheel speed sensor inputs are transmitted by the ABS module over the HS-CAN to the PAM and/or the PSCM . For non-hybrid vehicles, the vehicle speed and transaxle position are transmitted by the PCM over the HS-CAN to the PAM and/or the PSCM . For hybrid vehicles, the vehicle speed and wheel direction are transmitted by the Transmission Control Module (TCM) over the HS-CAN to the PAM and/or the PSCM . The PAM uses this data to calculate vehicle position and distance in relation to the parking space. The inputs are used by the PAM to command the steering system to assist with the steering wheel control to maneuver the vehicle into the parking space.

If the PSCM , the PCM, the TCM (hybrid only), and/or the ABS module malfunction, the active park assist system is disabled or prevents the system from activating. The message "ACTIVE PARK FAULT" or "ACTIVE PARK NOT AVAILABLE" is displayed in the IC message center and a DTC is set in the PAM .

The operator has full control of gear-shifting, the accelerator and the brake pedal. The IC message center displays the message "BACK UP USE CAUTION" as the vehicle enters the parking space.

The rear parking aid sensors are used to detect a vehicle or object located behind the vehicle in the parking space. The PAM determines the distance to the rear of the vehicle from the input signal from the rear parking aid sensors. The rear parking aid speaker sounds a continuous tone when the rear bumper of the vehicle is approximately 30 cm (12 in) from the vehicle to the rear and the message in the message center displays "PULL FORWARD USE CAUTION" followed by an audible chime from the IC .

When the transaxle is placed in DRIVE (D), the PAM receives the drive gear input message over the HS-CAN from the PCM. The active park assist system continues to control the steering as the operator moves the vehicle forward. When the front bumper of the vehicle is approximately 30 cm (12 in) from the front vehicle, the IC message center displays the message "BACK UP SLOWLY USE CAUTION" followed by an audible chime from the IC . The active park assist system may offer subsequent backward and forward maneuvers before finalizing the parking sequence.

The PAM determines that the active park maneuvers are completed based on the final vehicle alignment and the system has centered the steering wheel. The vehicle should be located approximately 0-30 cm (0-12 in) from the street curb if a curb is detected, otherwise the system aligns the vehicle to the front vehicle. The IC message center displays the message "ACTIVE PARK FINISHED" followed by an audible chime from the IC .

Pressing and releasing the active park assist switch at anytime disables the active park assist system and the IC message center displays the message "ACTIVE PARK CANCELLED".

The following conditions can result in the active park assist system being cancelled:

MESSAGE CENTER MESSAGE AND AUDIBLE CHIME REFERENCE CHART

Cancellation Event	Message Center Message And/Or Audible Chime
Grabbing the steering wheel while the active park assist system is controlling the steering.	CANCELLED BY DRIVER INPUT followed by a chime
Exceeding vehicle speed above 30 km/h (18 mph) during the measuring phase for 30 consecutive seconds.	ACTIVE PARK REDUCE SPEED
Exceeding vehicle speed above 10 km/h (6 mph) when the system is controlling the steering.	CANCELLED BY OVER SPEED followed by a chime
Deactivation of the AdvanceTrac® System by the operator, an ABS or AdvanceTrac® event has occurred while the system has control of the steering.	CANCELLED BY ABS EVENT, ACTIVE PARK DEACTIVATED or CANCELLED BY ADV TRAC EVENT followed by a chime
If any vehicle door (except the driver door) or liftgate is opened when the system is controlling the steering, if the operator engages DRIVE (D) before the vehicle is far enough inside the parking space, or the system cannot follow the desired steering path.	ACTIVE PARK DEACTIVATED followed by a chime

The active park assist system is not available if the following conditions exist:

A vehicle attachment is detected, such as a trailer or bike rack, by the active park assist sensors.
Any door (except the driver door) is ajar.
AdvanceTrac® has been deactivated by the operator before activating the active park assist system or an AdvanceTrac® or ABS event occurs when the active park assist system is activated.

The IC message center displays the message "ACTIVE PARK NOT AVAILABLE" followed by an audible chime.

The following conditions can cause the active park assist system to incorrectly align the vehicle in the selected parking space:

A spare tire is used or one of the vehicle's tires has significantly more or less tread wear than the other tires.
The factory-installed tire sizes are not used on the vehicle.
Poor weather conditions, such as heavy rain or snow.
If the active park assist sensors are damaged or obstructed.
There may be an irregular curb along the parking space.
The vehicle or objects bordering the space may not be positioned correctly. The system aligns the vehicle to the front vehicle when the curb is not detected.
The parking space length or parked objects position have changed after the vehicle has passed the parking space.
The temperature around the vehicle changes quickly such as the vehicle driven from a heated garage into the cold or just leaving a car wash before the system was used.
One of the parked vehicles has a high attachment, such as a salt spreader or moving truck bed, that the sensors cannot detect.

When a fault is present in the active park assist system, the PAM sends a network message to the IC and the IC message center displays the message "ACTIVE PARK FAULT" followed by a chime. This disables the active park assist system.