Mountaineer 2WD V8-4.6L SOHC VIN W (2003)
Information Bus: Description and Operation
Communications Network
Description and Operation
COMMUNICATIONS NETWORK
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. refer to Symptom Charts for diagnosis and testing of the PCM.
4-wheel Anti-Lock Brake (4WABS) Control Module
The 4WABS is on the SCP communication network. The 4WABS control module controls the brake pressure to the four wheels to keep the vehicle
under control while braking.
Restraint Control Module (RCM)
The RCM is on the ISO 9141 network. The RCM controls the deployment of the air bags based on sensor input.
Electronic Automatic Temperature Control (EATC) Module
The EATC module is on the SCP communication network. The EATC module controls automatic climate functions that maintain the vehicle interior
temperature at a constant setting.
Instrument Cluster
The instrument cluster is on the SCP communication network. The instrument cluster is also called a hybrid electronic cluster (HEC). It is an analog
face cluster with a digital odometer. The instrument cluster displays a variety of information.
Tire Pressure Monitor Module
The tire pressure monitor module is on the SCP communication network. The tire pressure monitor module uses one sensor mounted in each tire to
sense low tire pressure. When low tire pressure is sensed the module will send a warning to the driver.
Driver Seat Module (DSM)
The DSM is on the UBP communication network. The DSM controls the positioning and programming of the driver seat, pedals and both outside
mirrors.
Vehicle Security Module
The vehicle security module is on the UBP communication network. The vehicle security module controls the keyless entry functions for the vehicle.
Parking Aid Module
The parking aid module is connected to the ISO 9141 communication module. The module controls sensors in the rear bumper that detect close
objects when the vehicle is in reverse.
4-Wheel Drive (4WD) Control Module
The 4WD control module is on the UBP communications network. The 4WD control module engages and disengages the transfer case between 2WD
and 4WD when more traction is required.
Principles of Operation (How Does It Work?)
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 tool through the SCP communications network circuits