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Principles of Operation
The vehicle has three module communication networks: the standard corporate protocol (SCP), which is an unshielded twisted pair cable (data bus plus, [Circuit 914 (TN/OG)] and data bus minus, [Circuit 915 (PK/LB)]), the universal asynchronous receiver transmitter (UART) based protocol (UBP) (Circuit 693 [OG]) communications network and the international standards organization (ISO) 9141 communications network, which is a single wire network (Circuit 70 [LB/WH]). All three networks are connected to the data link connector (DLC). This makes diagnosis and testing of these systems easier by allowing one smart tester to be able to diagnose and control any module on the three 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 will 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.
Under normal operation the powertrain control module (PCM) communicates with the diagnostic cool through the SCP communications 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. Check circuits 914 (TN/OG) and 915 (PK/LB) 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 in circuit 914 (TN/OG) or 915 (PK/LB), damage to the DLC C251, damage to the PCM C175, or a problem in the in-line connector C1026.
The UBP communications network will not function if the wire is shorted to ground or voltage. The UBP is different from the ISO communication network in that it allows intermodule communication.
Vehicle Identification (VID) Block
Some PCMs contain a memory area called a vehicle identification (VID) block. The VID block is used to store powertrain configuration information.
As-Built Data Center
The As-Built Data Center maintains a record of the vehicle configuration in a database. The vehicle VIN is required to obtain this information. The As-Built Data Center records the applicable module configurations stored in each module before the vehicle leaves the factory. The As-Built Data Center will always reflect the original build of the vehicle as it left the factory. Only contact the As-Built Data Center when directed to do so by the WDS.
The vehicle security module controls the remote keyless entry system and computer-operated lock system. For additional information, refer to HANDLES, LOCKS, LATCHES AND ENTRY SYSTEMS .
The driver seat module (DSM) allows automatic positioning of the memory driver seat, both outside memory mirrors and the memory pedals to three programmable positions. For additional information, refer to SEATING .
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Refer to COMPUTER DATA LINES (Explorer) or COMPUTER DATA LINES (Mountaineer) .
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- Verify the customer concern.
- Visually inspect for obvious signs of mechanical or electrical damage.
- If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.
- If the cause is not visually evident, connect the diagnostic tool to the data link connector and select the vehicle to be tested from the diagnostic tool menu. If the diagnostic tool does not communicate with the vehicle: check that the program card is correctly installed. check the connections to the vehicle. check the ignition switch position.
- If the diagnostic tool still does not communicate with the vehicle, refer to the diagnostic tool operating manual.
- GO to Pinpoint Test PC.
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Normal Operation
The vehicle security module communicates with the diagnostic tool through the UART based protocol (UBP) communications network circuit 693 (OG). If circuit 693 (OG) becomes open or shorted to ground communications to that module will not be possible. Check circuit 693 (OG) between the vehicle security module C3008f 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 in circuit 693 (OG), damage to the DLC C251, damage to the vehicle security module C3008f, or a problem in the in-line connector C2095.
The 4WD control module communicates with the diagnostic tool through the UART based protocol (UBP) communications network circuit 693 (OG). If circuit 693 (OG) becomes open or shorted to ground communications to that module will not be possible. Check circuit 693 (OG) between the 4WD control module C281b 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 in circuit 693 (OG), damage to the DLC C251, damage to the 4WD control module C281b, or a problem in the in- line connectors C2108.
The RCM communicates with the diagnostic tool through the ISO 9141 communications network circuit 70 (LB/WH). If circuit 70 (LB/WH) becomes open or shorted to ground communications to that module will not be possible. Check circuit 70 (LB/WH) between the RCM C310a 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 in circuit 70 (LB/WH), damage to the DLC C251, or damage to the C310a.
The tire pressure monitor module communicates with the diagnostic tool through the SCP communications 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. Check circuits 914 (TN/OG) and 915 (PK/LB) between the tire pressure monitor module C3183 and the data link connector (DLC) C251. Total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms there is an open in circuit 914 (TN/OG) or 915 (PK/LB), damage to the DLC C251, damage to the tire pressure monitor module C3183, or a problem in the in-line connector C2095.
The DSM communicates with the diagnostic tool through the UART based protocol (UBP) communications network circuit 693 (OG). If circuit 693 (OG) becomes open or shorted to ground communications to that module will not be possible. Check circuit 693 (OG) between the DSM C341c 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 in circuit 693 (OG), damage to the DLC C251, damage to the DSM C341g, or a problem in the in-line connector C2095 or C3050.
The parking aid module communicates with the diagnostic tool through the ISO 9141 communications network circuit 70 (LB/WH). If circuit 70 (LB/WH) becomes open or shorted to ground communications to that module will not be possible. Check circuit 70 (LB/WH) between the parking aid module C4014 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 in circuit 70 (LB/WH), damage to the DLC C251, damage to the parking aid module C4014, or a problem in the in-line connector C2095 or C408.
The PCM communicates with the diagnostic tool through the SCP communications 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. Check circuits 914 (TN/OG) and 915 (PK/LB) between the PCM C175a and the data link connector (DLC) C251. Total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms there is an open in circuit 914 (TN/OG) or 915 (PK/LB), damage to the DLC C251, damage to the PCM C175a, or a problem in the in-line connector C263.
The instrument cluster communicates with the diagnostic tool through the SCP communications 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. Check circuits 914 (TN/OG) and 915 (PK/LB) between the instrument cluster C220b and the data link connector (DLC) C251. Total resistance values must not be more than 5 ohms. If the resistance is more chan 5 ohms there is an open in circuit 914 (TN/OG) or 915 (PK/LB), damage to the DLC C251, or damage to the instrument cluster C220b.
Under normal operation the EATC module communicates with the diagnostic tool through the SCP communications 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. Check circuits 914 (TN/OG) and 915 (PK/LB) between the EATC module C228b and the data link connector (DLC) C251. Total resistance values must not be more than 5 ohms. If the resistance is more than 5 ohms there is an open in circuit 914 (TN/OG) or 915 (PK/LB), damage to the DLC C251, or damage to the EATC module C228b.
The ABS/TC module or stability assist module communicates with the diagnostic tool through the SCP communications 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. Check circuits 914 (TN/OG) and 915 (PK/LB) between the ABS/TC module or stability assist 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 in circuit 914 (TN/OG) or 915 (PK/LB), damage to the DLC C251, damage to the ABS/TC module or stability assist module C155, or a problem in the in-line connector C263 or C126.
The powertrain control module (PCM), ABS/TC module or stability assist module, electronic automatic temperature control (EATC) module, tire pressure monitor module, and the instrument cluster communicate with the diagnostic tool through the SCP communications network circuits 914 (TN/OG) and 915 (PK/LB). 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. If a module is lost due to internal concerns, communications can continue to all other modules. Check circuits 914 (TN/OG) and 915 (PK/LB) between the PCM C175a, tire pressure monitor module C3183, ABS/TC module or stability assist module C155, EATC module C228b, instrument cluster C220b, 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 in circuit 914 (TN/OG) or 915 (PK/LB), damage to the DLC C251, damage to the PCM C175a, tire pressure monitor module C3183, ABS/TC module or stability assist module C155, EATC module C228b, instrument cluster C220b, a problem in the in- line connectors C2095, C263, C126 or an internal problem with the PCM, ABS/TC module or stability assist module, EATC module, tire pressure monitor module, or the instrument cluster. 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 links 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 reverse parking aid module and the restraint control module (RCM) communicate with the diagnostic tool through the ISO 9141 communications network circuit 70 (LB./WH). If circuit 70 (LB/WH) becomes open or shorted to ground, communications to that module will not be possible. Check circuit 70 (LB/WH) between the parking aid module, RCM 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 in circuit 70 (LB/WH), damage to the DLC C251, damage to the parking aid module, RCM, or a problem in one of the in-line connectors C2095 or C408. 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 links 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 driver seat module (DSM), vehicle security module, and the 4-wheel drive (4WD) control module communicate with the diagnostic tool through the UART based protocol (UBP) communications network circuit 693 (OG). If circuit 693 (OG) becomes open or shorted to ground, communications to that module will not be possible. Check circuit 693 (OG) between the DSM, vehicle security module, and the 4WD control module 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 in circuit 693 (OG), damage to the DLC C251, damage to the DSM, vehicle security module, the 4WD control module, instrument cluster, or a problem in one of the in-line connectors C2095, C2108 or C408. 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 links 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 instrument cluster communicates with the diagnostic tool through the UART based protocol (UBP) communications network circuit 693 (OG). If circuit 693 (OG) becomes open or shorted to ground communications to that module will not be possible. Check circuit 693 (OG) between the instrument cluster 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 in circuit 693 (OG), damage to the DLC C251, damage to the instrument cluster C220b.
The diagnostic tool is connected to the DLC C251 to communicate with the standard corporate protocol (SCP), UART based protocol (UBP), and the International standards organization (ISO) 9141 communications networks. If communication can not be established, the diagnostic tool and the DLC C251 must be checked for damaged. If the diagnostic tool and the DLC C251 are ok circuits 1001 (WH/YE), 1205 (BK), and 570 (BK/WH) must be checked for an open condition.
The power driver seat is controlled by the DSM only when the vehicle is equipped with the programmable/recall memory option. Power is supplied through central junction box (CJB) fuses: 20 (5A), 1 (30A) and battery junction box (BJB) fuse 29 (60A) and 1 (60A) on Circuits 1003 (GY/YE), 566 (DG) and grounded through circuit 1203 (BK/LB) and 1205 (BK).
The vehicle security module controls the remote keyless entry and computer- operated locks and vehicle security. The vehicle security module receives power through BJB fuses 2 (30A) and CJB fuse 2 (10A). From the fuses power is delivered to the module through circuits 456 (DG/OG), 645 (WH/LB) and is grounded on circuit 1205 (BK).