Crown Victoria V8-4.6L CNG SOHC VIN 9 (1999)
Multiplex Communication Network: Pinout Values and Diagnostic Parameters
Inspection and Verification (Start Here)
1. Verify the customer concern by operating the system in question.
2. Visually inspect for obvious signs of electrical damage.
VISUAL INSPECTION CHART
Electrical
^
Battery Junction Box (BJB) Fuse 12 (30 A)
^
Wiring harness
^
Loose or corroded connections
^
Anti-lock brake control module
^
Electronic Automatic Temperature Control (EATC) module
^
Passive Anti-Theft System (PATS) module
^
Natural Gas Vehicle Module (NGVM)
^
Electronic Crash Sensor (ECS)
^
Driver Door Module (DDM)
^
Lighting Control Module (LCM)
^
Powertrain Control Module (PCM)
3. If the concern remains after the inspection, connect NGS Tester to the DLC located beneath the instrument panel and select the vehicle to be tested
from the NGS Tester menu. If NGS Tester does not communicate with the vehicle:
^
Check that the program card is correctly installed.
^
Check that the correct version of the program card is installed.
^
Check the connections to the vehicle.
^
Check the ignition switch position.
If NGS Tester still does not communicate with the vehicle, GO to Pinpoint Test N.
4. GO to Pinpoint Test PC. See: Module Communication Network/System Precheck
Principles of Operation
The vehicle has two module communication networks. The Standard Corporate Protocol (SCP) communication network, which is an unshielded twisted
pair cable (data bus plus, Circuit 914 [TN/OG] and data bus minus, Circuit 915 [PK/LB]) and the International Standards Organization (ISO) 9141
communications network which is a single-wire network(Circuit 70 [LB/W]). Both networks can be connected to New Generation STAR (NGS) Tester
by one connector called the Data Link Connector (DLC). This makes diagnosis and testing these systems easier by allowing one smart tester to be able to
diagnose and control any module on the two networks from one connector. The DLC can be found under the instrument panel between the steering
column and the radio.
The ISO 9141 communication network does not permit intermodule communication. When NGS Tester communicates to modules on the ISO 9141
communication network, NGS Tester must ask for all information; the modules cannot initiate communications.
The SCP communication 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 battery positive voltage (B+), or if some but not all termination resistors are lost.
Unlike the SCP communication network, the ISO 9141 communication network will not function if the wire is shorted to ground or battery positive
voltage (B+). Also, if one of the modules on the ISO 9141 communication network loses power or shorts internally, communications to that module will
