Ford F150 Pickup. Instruction — part 15

Principles of Operation

The vehicle has two 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)]
and the international standards organization (ISO) 9141 communications network, which is a single wire
network (circuit 70 [LB/WH]). Both 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 two 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 inter-module 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 powertrain control module (PCM) is on the SCP communication network. The PCM controls the engine for
better fuel economy, emissions control, and failure mode detection and storage. Refer to POWERTRAIN
CONTROL MODULE for diagnosis and testing of the PCM.

The natural gas vehicle module (NGVM) if equipped is on the SCP communication network. The NGVM
calculates fuel level based on inputs from the fuel tank pressure sensor and the fuel tank temperature sensor.
The NGVM then provides a voltage signal to the instrument cluster to drive the fuel gauge. The NGVM also
has separate injector drivers to run the injectors at the higher operating pressure of natural gas. The NGVM does
not perform any calculations for this function; calibration for the injectors is maintained in the PCM. Refer to
NATURAL GAS VEHICLE MODULE for diagnosis and testing of the NGVM.

The restraint control module (RCM) is on the ISO 9141 network. The RCM controls the deployment of the air
bags and pretensioners based on sensor input. Refer to AIR BAG RESTRAINT SYSTEMS - F150 PICKUP .

The generic electronic module (GEM) is on the ISO 9141 network. The GEM is equipped on vehicles with 4-
wheel drive or vehicles with power windows. The GEM controls additional functions that include:

z

speed-dependent windshield wipers

z

4-wheel electronic shift on-the-fly

z

one-touch down power window

z

belt minder (if equipped)

Refer to MULTIFUNCTION ELECTRONIC MODULE .

2003 Ford Pickup F150

2003 ACCESSORIES AND EQUIPMENT Module Communications Network - F150 Pickup

The central security module is on the ISO 9141 communication network. The central security module controls
keyless entry and door lock/unlock functions for the vehicle. Refer to HANDLES, LOCKS, LATCHES AND
ENTRY SYSTEMS .

System Precheck

The 4-wheel anti-lock brake (4WABS) control module (if equipped) is on the ISO 9141 communication
network. The 4WABS control module controls the brake pressure to the four wheels to keep the vehicle under
control while braking. Refer to ANTI-LOCK CONTROL-4-WHEEL .

The instrument cluster is also known as a hybrid electronic cluster (HEC) and is on the SCP communication
network. The instrument cluster displays driver information. Refer to INSTRUMENT CLUSTER-
CONVENTIONAL - F150 .

Inspection and Verification

1. Verify the customer concern.

2. Visually inspect for obvious signs of electrical damage.

Fig. 3: Visual Inspection Chart
Courtesy of FORD MOTOR CO.

3. If the concern remains after the inspection, connect the diagnostic tool to the data link connector (DLC),

located beneath the instrument panel, and select the vehicle to be tested from the diagnostic tool menu. If
the diagnostic tool does not communicate with the vehicle:

z

check that the program card is correctly installed and the correct version is used.

z

check the connections to the vehicle.

z

check the ignition switch position.

If the diagnostic tool still does not communicate with the vehicle, go to Pinpoint Test J.

4. Go to Pinpoint Test PC.

2003 Ford Pickup F150

2003 ACCESSORIES AND EQUIPMENT Module Communications Network - F150 Pickup

Fig. 4: Pinpoint Test PC: Data Link Diagnostics Network Test (PC1)
Courtesy of FORD MOTOR CO.

Fig. 5: Pinpoint Test PC: Data Link Diagnostics Network Test (PC1 Cont.)
Courtesy of FORD MOTOR CO.

Symptom Chart

2003 Ford Pickup F150

2003 ACCESSORIES AND EQUIPMENT Module Communications Network - F150 Pickup

Fig. 6: Communications Network Symptom Chart (1 Of 2)
Courtesy of FORD MOTOR CO.

Fig. 7: Communications Network Symptom Chart (2 Of 2)
Courtesy of FORD MOTOR CO.

Pinpoint Tests

PINPOINT TEST A: 4-WHEEL ANTI-LOCK BRAKE (4WABS) CONTROL MODULE

2003 Ford Pickup F150

2003 ACCESSORIES AND EQUIPMENT Module Communications Network - F150 Pickup