Principles of Operation
The vehicle has 3 module communication networks: standard corporate protocol (SCP), which is an unshielded twisted pair cable data bus plus and data bus minus, the universal asynchronous receiver-transmitter (UART)-based protocol (UBP) communication network, a single wire network, and the international standards organization (ISO) 9141 communication 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 1 diagnostic tester to be able to diagnose and control any module on the 3 networks from 1 connector. The DLC can be found under the instrument panel between the steering column and the radio.
The SCP communication network remains operational even with the severing of 1 of the bus wires. Communications can also continue if 1 of the bus wires is shorted to ground or voltage, or if some but not all termination resistors are lost.
The ISO 9141 communication 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 communication network does not function if the wire is shorted to ground or battery voltage. Also, if 1 of the modules on the ISO 9141 communication network loses power or shorts internally, communications to that module fail.
The UBP communication network does not function if the wire is shorted to ground or voltage. The UBP communication network allows intermodule communication.
Normal Operation
The SJB communicates with the diagnostic tool through the standard corporate protocol (SCP) communication network circuits 914 (TN/OG) and 915 (PK/LB). 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. The 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 data link connector (DLC) C251, or damage to the SJB C2280b.
The SJB fused power (overload protected) is supplied by the bussed electrical center (BEC). Circuits 1052 (TN/BK), 1523 (DG), and 1524 (DB) supply power to the SJB. The SJB is grounded through circuit 1205 (BK).
The DSM communicates with the diagnostic tool through the universal asynchronous receiver-transmitter (UART)-based protocol (UBP) network circuit 2077 (PK/LB). If circuit 2077 (PK/LB) becomes open or shorted to ground, communications to that module are not possible. Check circuit 2077 (PK/LB) between the DSM C341c and the data link connector (DLC) C251. The total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open in circuit 2077 (PK/LB), damage to the DLC C251, damage to the DSM C341c, or a problem in the in-line connectors.
The DSM fused power (overload protected) is supplied through the following bussed electrical center (BEC) fuses: 10 (30A), circuit 566 (DG), and fuse 51 (10A) on circuit 1567 (RD/LB). The DSM ground circuits are circuit 1203 (BK/LB) and 1205 (BK).
The PCM communicates with the diagnostic tool through the standard corporate protocol (SCP) communication network circuits 914 (TN/OG) and 915 (PK/LB). 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 SCP circuits 914 (TN/OG) and 915 (PK/LB) between the PCM C175 and the data link connector (DLC) C251. The total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is either an open in the SCP network circuits, damage to the DLC C251, damage to the PCM C175, or a problem in the in-line connector.
The instrument cluster communicates with the diagnostic tool through the standard corporate protocol (SCP) communication network circuits 914 (TN/OG) and 915 (PK/LB). 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 circuits 914 (TN/OG) and 915 (PK/LB) between the instrument cluster C220a and the data link connector (DLC) C251. The total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open in the SCP circuits, damage to the DLC C251, damage to the instrument cluster C220a, or a problem in the in-line connectors.
The RCM communicates with the diagnostic tool through the international standards organization (ISO) 9141 communication network 9141 communication network circuit 70 (LB/WH). If circuit 70 (LB/WH) becomes open or shorted to ground communications to that module are not possible. Check circuit 70 (LB/WH) between the RCM C310a and the data link connector (DLC) C251. The total resistance value must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open in circuit 70 (LB/WH), damage to the DLC C251, or damage to the RCM C310a.
The ABS module communicates with the diagnostic tool through the standard corporate protocol (SCP) communication network circuits 914 (TN/OG) and 915 (PK/LB). 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 circuits 914 (TN/OG) and 915 (PK/LB) between the ABS module C155 and the data link connector (DLC) C251. The total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open in the SCP network circuits, damage to the DLC C251, damage to the ABS module C155, or a problem in the in-line connectors.
The DATC module communicates with the diagnostic tool through the standard corporate protocol (SCP) communication network circuits 914 (TN/OG) and 915 (PK/LB). 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 circuits 914 (TN/OG) and 915 (PK/LB) between the DATC module C228a and the data link connector (DLC) C251. The total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open in the SCP network circuits, damage to the DLC C251, the DATC module C228a, or a problem in the in-line connectors.
The speed control actuator communicates with the diagnostic tool through the standard corporate protocol (SCP) communication network circuits 914 (TN/OG) and 915 (PK/LB). 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 circuits 914 (TN/OG) and 915 (PK/LB) between the speed control actuator C122 and the data link connector (DLC) C251. The 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.
Two versions of this system are available, reverse parking aid with 4 sensors (rear only), and parking aid with 8 sensors (4 additional front sensors). Both type of parking aid modules communicate with the diagnostic tool through the international standards organization (ISO) 9141 communication network circuit 70 (LB/WH). If circuit 70 (LB/WH) becomes open or shorted to ground, communications to that module are not possible. Check circuit 70 (LB/WH) between the parking aid module C4014 (8 sensor) or C4226 (4 sensor), and the data link connector (DLC) C251. The total resistance value must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open in circuit 70 (LB/WH), damage to the DLC C251, damage to the parking aid module connector, or a problem in the in-line connectors.
The driver or passenger climate controlled seat module communicates with the diagnostic tool through the universal asynchronous receiver-transmitter (UART)-based protocol (UBP) network circuit 2077 (PK/LB). If the UBP circuit becomes open or shorted to ground communications to that module are not possible. Check circuit 2077 (PK/LB) between the climate controlled seat module and the data link connector (DLC) C251. The total resistance value must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open in UBP network circuit, damage to the DLC C251, damage to the climate controlled seat module connector, or a problem in the in-line connectors.
The RH PSD module and the LH PSD modules are both connected to the international standards organization (ISO) 9141 communication network. If the ISO 9141 communication network circuit becomes open or shorted to ground communication to that module are not possible. The ISO 9141 communication network does not function if the wire is shorted to ground or battery voltage. Check the network circuit between the PSD module in question and the data link connector (DLC) C251. The 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 9141 communication network, damage to the DLC C251, damage to the PSD module connector, or a problem in the in-line connector.
The power liftgate module is connected to the international standards organization (ISO) 9141 communication network. If circuit 70 (LB/WH) becomes open or shorted to ground, communications to that module are not possible. Check circuit 70 (LB/WH) between the power liftgate module C4174a and the data link connector (DLC) C251. Total resistance value must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open in circuit 70 (LB/WH), damage to the DLC C251, damage to the power liftgate module C4174a, or a problem in the in-line connectors.
The driver climate control seat module, passenger climate control seat module, dual automatic temperature control (DATC) module, and the driver seat module (DSM) communicate with the diagnostic tool through the UBP communications network circuit 2077 (PK/LB). If the UBP circuit becomes open or shorted to ground, communications to that module are not possible. Check circuit 2077 (PK/LB) between the driver climate control seat module, passenger climate control seat module, DATC module, DSM and the data link connector (DLC) C251. The total resistance value must not be more than 5 ohms. If the resistance is more than 5 ohms, there is either an open in circuit 2077 (PK/LB), damage to the DLC C251, damage to one of the networked modules, or a problem in one of the in-line connectors. If, after individual checks of each circuit leading to a module show resistance values less than 5 ohms, and no in-line connector issues are present, the data link diagnostics test must be run with the module in question disconnected. If the data link diagnostics test passes with the module in question disconnected, it is the source of the concern and should be removed and a new module installed.
The restraints control module (RCM), parking aid module, RH or LH power sliding door (PSD) module, and the power liftgate module communicate with the diagnostic tool through the ISO 9141 communication network circuit 70 (LB/WH). If the ISO 9141 communication network circuit becomes open or shorted to ground, communications to that module are not possible. Check circuit 70 (LB/WH) between the networked modules and the data link connector (DLC) C251. If, after individual checks of each circuit leading to a module show resistance values less than 5 ohms, and no in-line connector issues are present, the data link diagnostics test must be run with the module in question disconnected. If the data link diagnostics test passes with the module in question disconnected, it is the source of the concern and should be removed and a new module installed.
The smart junction box (SJB), powertrain control module (PCM), instrument cluster, anti-lock brake (ABS) module, dual automatic temperature control (DATC) module (or the function selector switch), and the speed control actuator communicate with the diagnostic tool through the SCP communications network circuits. If one of the bus wires become shorted to ground or voltage, or if some but not all termination resistors are lost, communications can continue at a degraded level. If a module is lost due to internal concerns, communications can continue to all other modules. Check the SCP communications network circuits between the networked modules and the data link connector (DLC) C251. The total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms, there is an open in one or both SCP communication network circuits, damage to the module connector, a problem with a in-line connector, or a problem with the DLC C251. If, after individual checks of each circuit leading to a module show resistance values less than 5 ohms, and no in-line connector issues present, the data link diagnostics test must be run with the module in question disconnected. If the data link diagnostics test passes with the module in question disconnected, it is the source of the concern and should be removed and a new module installed.
Under normal operation the diagnostic tool is connected to the data link connector (DLC) C251 to communicate with the standard corporate protocol (SCP), UART-based protocol (UBP), and the international standards organization (ISO) 9141 communication network. If communication cannot be established, the diagnostic tool and the DLC C251 must be checked for damage. If the diagnostic tool and the DLC C251 are OK, circuit 40 (LB/WH) must be checked for voltage and 1205 (BK), and 1203 (BK/LB) must be checked for an open condition.
See also:
• SUPPLEMENTAL RESTRAINT SYSTEM