Communications Network
COMMUNICATIONS NETWORKSmart Junction Box (SJB)
The smart junction box (SJB) is connected to the standard corporate protocol (SCP) communication network. The SJB controls both interior and exterior lighting, body functions, and active anti-theft functions. In the absence of the dual automatic temperature control (DATC) module, the SJB receives input from the function selector switch to operate the manual climate control system. If one of the bus wires becomes shorted to ground or voltage, communications can continue at a degraded level. Check circuits 914 (TN/OG), and 915 (PK/LB ) between the SJB C2280b and the DLC C251. Total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the SCP network, damage to the DLC C251, or damage to the SJB C2280b. The SJB is a combination of a multifunction control module and an interior power junction box. SJB functions control multiple systems which include:
- illuminated entry and interior lamps
- exterior lamps
- perimeter alarm
- power door locks
- auto-locks and smart locks
- keyless entry keypad
- remote keyless entry (RKE)
- warning chimes
The SJB is equipped on all vehicles and is located behind the LH dash closeout panel.
Driver Seat Module (DSM)
The DSM is on the universal asynchronous receiver-transmitter (UART)-based protocol (UBP) communication network, circuit 2077 (PK/LB). The DSM controls the positioning and programming of the driver seat and memory exterior rear view mirrors. The UBP communication network will not function if the wire is shorted to ground or battery voltage. Check the network circuit between the DSM C341c and the DLC C251. Total resistance value must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the UBP network, damage to the DLC C251, damage to the DSM C341c, or a problem in the in-line connector. The DSM is located under the driver seat.
Powertrain Control Module (PCM)
The PCM is on the SCP communication network. The PCM controls the engine for better fuel economy, emissions control, failure mode detection and storage, and all passive anti-theft system (PATS) functions. If one of the bus wires becomes shorted to ground or voltage, or if some but not all termination resistors are lost, communications can continue at a degraded level. Check the SCP circuits 915 (PK/LB) and 914 (TN/OG) between the PCM C175 and the DLC C251. Total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the SCP network, damage to the DLC C251, damage to the PCM C175, or a problem in the in-line connector.
Instrument Cluster
The instrument cluster is on the SCP communication network. It is an analog face cluster with a digital odometer. The instrument cluster displays a variety of information. If one of the bus wires becomes shorted to ground or voltage, or if some but not all termination resistors are lost, communications can continue at a degraded level. Check the SCP circuits 915 (PK/LB) and 914 (TN/OG) between the instrument cluster C220a and the DLC C251. Total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the SCP network, damage to the DLC C251, damage to the instrument cluster C220a, or a problem in the in-line connector.
Restraint Control Module (RCM)
The restraint control module (RCM) is on the international standards organization (ISO) 9141 network. The RCM controls the deployment of the air bags based on sensor input. The ISO communication network will not function if the wire is shorted to ground or battery voltage. Check the network circuit between the RCM C310a and the DLC C251. Total resistance value must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the ISO network, damage to the DLC C251, damage to the RCM C310a, or a problem in the in-line connector.
Anti-Lock Brake System (ABS) Module
The ABS Module is on the SCP communication network. The ABS module controls the brake pressure to the four wheels to keep the vehicle under control while braking. The ABS module also controls the stability assist and traction control systems (if equipped). If one of the bus wires becomes shorted to ground or voltage, or if some but not all termination resistors are lost, communications can continue at a degraded level. Check the SCP circuits 915 (PK/LB) and 914 (TN/OG) between the ABS module C155 and the DLC C251. Total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the SCP network, damage to the DLC C251, damage to the ABS module C155, or a problem in the in-line connector.
Dual Automatic Temperature Control (DATC) Module
The DATC module uses the SCP communication network for communication with the diagnostic tool. The DATC module controls automatic climate functions that maintain the vehicle interior temperature at a constant setting. The DATC module also uses the UBP network for communication with the driver or passenger climate controlled seat modules. If one of the bus wires becomes shorted to ground or voltage, or if some but not all termination resistors are lost, communications can continue at a degraded level. Check the SCP circuits 915 (PK/LB) and 914 (TN/OG) between the DATC module C228a and the DLC C251. Total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the SCP network, damage to the DLC C251, damage to the DATC module C228a, or a problem in the in-line connector.
Speed Control Actuator
The speed control actuator is connected to the SCP communication network. The speed control system is designed to maintain vehicle speed between 48 and 200 km/h (30 and 125 mph). If one of the bus wires becomes shorted to ground or voltage, or if some but not all termination resistors are lost, communications can continue at a degraded level. Check the SCP circuits 915 (PK/LB) and 914 (TN/OG) between the speed control actuator C122 and the DLC C251. Total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the SCP network, damage to the DLC C251, damage to the speed control actuator C122, or a problem in the in-line connector.
Parking Aid Modules - Four Sensor and Eight Sensor
The parking aid module is connected to the ISO 9141 network. Two versions of this system are available, reverse parking aid with four sensors (rear only), and parking aid with eight sensors (four additional front sensors). The reverse parking aid module controls sensors in the rear bumper that detect close objects when the transmission is in REVERSE. The second parking aid system incorporates additional front sensors that are operational when the transmission is in DRIVE, and vehicle speed is above 0 km/h and below 8 km/h. The ISO communication network will not function if the wire is shorted to ground or battery voltage. Check the network circuit between the parking aid module C4426 (or C4014 with front sensors) and the DLC C251. Total resistance value must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the UBP network, damage to the DLC C251, damage to the parking aid module is connector, or a problem in the in-line connector.
Driver or Passenger Climate Controlled Seat Module
The driver or passenger climate controlled seat module is on the UBP communications network. The climate controlled seat modules communicate with the DATC module to control the heating and cooling elements in the seat for driver/passenger comfort. The UBP communication network will not function if the wire is shorted to ground or battery voltage. Check the network circuit between the climate controlled seat module C3031a (driver), C3036a (passenger), and the DLC C251. Total resistance value must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the UBP network, damage to the DLC C251, damage to the climate controlled seat module connector, or a problem in the in-line connector.
Right Hand (RH) and Left Hand (LH) Power Sliding Door (PSD) Modules
The RH PSD module and the LH PSD modules are both connected to the ISO 9141 communication network. The modules control opening and closing of the right and left passenger side doors. The ISO communication network will not function if the wire is shorted to ground or battery voltage. Check the network circuit between the PSD module in question and the DLC C251. Total resistance value must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the ISO network, damage to the DLC C251, damage to the PSD module connector, or a problem in the in-line connector.
Power Liftgate Module
The power liftgate module is connected to the ISO 9141 communication network. The module controls opening and closing of the vehicle liftgate. The ISO communication network will not function if the wire is shorted to ground or battery voltage. Check the network circuit between the power liftgate module and the DLC C251. Total resistance value must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open circuit in the ISO network, damage to the DLC C251, damage to the power liftgate module C4174, or a problem in the in-line connector.
PRINCIPLES OF OPERATION
The vehicle has 3 module communication networks: SCP, which is an unshielded twisted pair cable data bus plus and data bus minus, the UBP communications network, a single wire network and the ISO 9141 communications network, which is a single wire network. All 3 networks are connected to the data link connector (DLC) C251. This makes diagnosis and testing of these systems easier by allowing one diagnostic tester to be able to diagnose and control any module on the 3 networks from one connector. The DLC can be found under the instrument panel between the steering column and the radio.
The SCP communications network will remain operational even with the severing of one of the bus wires. Communications can also continue if one of the bus wires is shorted to ground or voltage, or if some but not all termination resistors are lost.
The ISO 9141 communications network does not permit intermodule communication. When the diagnostic tool communicates to modules on the ISO 9141 communication network, the diagnostic tool must ask for all information; the modules cannot initiate communications. The ISO 9141 communications network will not function if the wire is shorted to ground or battery voltage. Also, if one of the modules on the ISO 9141 communications network loses power or shorts internally, communications to that module will fail.
The UBP communications network will not function if the wire is shorted to ground or voltage. The UBP network allows intermodule communication.