Manual or electronic t case?
Section 07-07: Transfer Case, 4x4 System, Service
1994 Bronco/Econoline/F-Series Workshop Manual
DESCRIPTION AND OPERATION
Electronic Shift Operation
The transfer case is equipped with a magnetic clutch, similar to an air conditioning compressor clutch, which is located inside the transfer case adjacent to the lockup collar. The clutch is used to spin up the front drive system from zero to vehicle speed in milliseconds. This spin-up allows the shift between 2-high and 4-high to be made at vehicle speeds listed in the vehicle owner's guide. The spin up engages the front lock hubs. When the transfer case rear and front output shafts reach synchronous speed, the spring-loaded lockup collar mechanically engages the mainshaft hub to the chain drive sprocket and the magnetic clutch is then deactivated. Shifts between 4-high and 4-low can only occur with the transmission safety switches closed. The vehicle's speed must also be within specified limits as determined by the transfer case speed sensor (3 mph or under).
Electronic Shift Control System
This system consists of a two-switch control system, an electronic control module, an electric shift motor (7G360) with an integral shift position sensor, and a speed sensor.
Switch Control System
There are two control switches located on the upper right corner of the instrument panel for fingertip shift control. The two switches are mounted horizontally and are identified as "4x4" and "LOW RANGE". Two indicator bar lamps are located in the instrument cluster.
When either of the two switches on the instrument panel control are depressed, the first thing that happens is that the electronic control module receives input from the transfer case shift position sensor to verify what position the transfer case is in (2H, 4H or 4L). Next, the electronic control module looks at the speed sensor and the park/neutral position switch or clutch pedal position switch (depending on transmission type). If all conditions are correct to allow the desired shift, the electronic control module will tell the electric shift motor to execute the shift. After the shift has been made and the electric shift motor is off, the control module again looks at the shift position sensor to make sure the proper shift has been accomplished. Finally, the dash indicator light and the pushbutton light on the control panel will be illuminated by a signal from the electronic control module indicating the desired function has been completed.
Electronic Control Module
The electronic control module, located on the passenger side, controls the operation of the transfer case in response to inputs to the pushbutton control by the vehicle operator, the speed sensor, shift position sensor and the park/neutral position switch.
Speed Sensor
The speed sensor, mounted on the rear of the transfer case , tells the electronic control module the speed of the vehicle to allow range shifts (in or out of 4L) to occur.
Shift Position Sensor
The shift position sensor, an integral part of the electric shift motor , tells the electronic control module the shift position of the transfer case .
Electric Shift Motor
The electric shift motor , mounted externally at the rear of the transfer case , drives a rotary helical cam which moves the 2W-4W shift fork and 4H-4L reduction shift fork to the selected vehicle drive position.
On-Board Diagnostics
Control Module
The electronic control module has a diagnostic capability of its own circuitry. To perform procedure: Remove the five-wire connector and the eight-wire connector from the bottom of the electronic control module.
Turn the ignition switch (11572) to the RUN position.
Activate the self-test switch located on the module and note the result: a flashing indicator lamp (approximately one flash per second) indicates that the control module is functioning properly. A steady indicator lamp indicates that the control module is inoperative and must be replaced.
Circuits, Control Module
There are three wiring harnesses connected to the electronic control module: the eight-wire pigtail harness connector; the five-wire harness connector; and the eight-wire harness connector.
To check the integrity of these circuits, disconnect the harnesses from the electronic control module and perform the following checks.
Harness Connector, Eight-Wire Pigtail
CAUTION: In the following sections where the use of an ohmmeter is specified, remember that an ohmmeter should NEVER be connected into a "live" or powered circuit. If the ohmmeter is subjected to a powered circuit, severe damage will be done to the instrument. The vehicle's battery should be disconnected before performing checks on any circuit with an ohmmeter to prevent any accidental damage to the instrument.
NOTE: When the battery is disconnected and reconnected, some abnormal drive symptoms may occur while the powertrain control module (PCM) (12A650) relearns its adaptive strategy. The vehicle may need to be driven 10 miles or more to relearn the adaptive strategy.
NOTE: When connecting ohmmeter to ground, care must be taken to ensure good contact or false meter readings may result. Connect a voltmeter between terminal 8 and ground. The voltmeter should indicate battery voltage at all times.
Connect a voltmeter between terminal 7 and ground. Then turn the ignition switch to the RUN position. The voltmeter should then indicate battery voltage.
Connect a suitable ohmmeter between terminal 6 and ground. The ohmmeter should indicate less than 10 ohms.
Connect an ohmmeter between terminals 4 and 5 of the wiring harness connector. The ohmmeter should indicate less than 10 ohms.
Connect an ohmmeter between terminal 3 and ground. The ohmmeter should indicate 0 ohms.
Connect an ohmmeter between terminal 2 and ground. The ohmmeter should indicate 0 ohms.
Item Part Number Description 1 Open Open 2 57 (Blk) Ground 3 570 (Blk) Logic Ground 4 778 (Org) Transfer Case Motor Control (Clockwise) 2H-4H-4L 5 777 (Yel) Transfer Case Motor Control (Counterclockwise) 4L-4H-2H 6 779 (Brn) Electro-Magnetic Clutch (Feed) 7 296 (Wht/Ppl) Ignition Run and Accessory Feed (Fused) 8 517 (Blk/Wht) Battery Feed (Circuit Breaker)
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