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randyjaneway
randyjaneway, ASE Certified Technician
Category: Ford
Satisfied Customers: 188
Experience:  20 years in Electrical and A/C
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91 ford ranger: push button 4x4 4wd..low range with a test light

Customer Question

i have a 91 ford ranger push button 4x4 4wd is not working niether is low range with a test light in the plug under truck nothing has power even while pushing the button
Submitted: 7 years ago.
Category: Ford
Expert:  randyjaneway replied 7 years ago.

4x4 on this model is controlled by a module. I will attempt to include wiring schematics:

 

 

The module is located in the left rear of the vehicle cab.

Usually, when the transfer case doesn't shift, the problem is with the shift motor.

Also, here is a pinpoint test for you to perform.

There are three wiring harnesses connected to the Electronic Control Module (ECM) :

  • The Eight-Wire Pigtail Harness Connector.
  • The Five-Wire Harness Connector.
  • The Eight-Wire Harness Connector.

To check the integrity of these circuits, disconnect the harnesses from the ECM and perform the following checks:

EIGHT-WIRE PIGTAIL HARNESS CONNECTOR

Eight-wire Pigtail Harness Connector (Electronic Shift) C302

  1. Connect a voltmeter between terminal 8 and ground . The voltmeter should indicate battery voltage at all times.
  2. Connect a voltmeter between terminal 7 and ground , then turn ignition switch to RUN position. The voltmeter should indicate battery voltage. CAUTION: In the following sections where the usage of an ohmmeter is specified, always 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.
  3. Connect an ohmmeter between terminal 6 and ground . The ohmmeter should indicate less than 10 ohms resistance .
  4. Connect an ohmmeter between terminals 4 and 5 . The ohmmeter should indicate less than 10 ohms resistance .
  5. Connect an ohmmeter between terminal 3 and ground . The ohmmeter should indicate 0 ohms .
  6. Connect an ohmmeter between terminal 2 and ground . The ohmmeter should indicate 0 ohms .

FIVE-WIRE PIGTAIL HARNESS CONNECTOR

Fig. 7 Five-wire Pigtail Harness Connector (Electronic Shift) C300

  1. Connect an ohmmeter between terminals 1 and 2 , then DEPRESS the 4x4 (2H-4H) switch . The ohmmeter should indicate a very "low" resistance value (less than 50 ohms) while the switch is being DEPRESSED.
  2. Connect ohmmeter between terminals 1 and 3 , then DEPRESS the Low Range switch . The ohmmeter should indicate a very "low" resistance value (less than 50 ohms) while the switch is being DEPRESSED.
  3. Connect a test lead between terminals 4 and ground , then turn ignition switch to RUN position and observe the indicator lights. The light in the instrument panel and Low Range Bar should illuminate .
  4. Connect a test lead between terminal 5 and ground , then turn ignition switch to RUN and observe the indicator lights. The lights in the instrument panel and 4x4 Bar should illuminate .

EIGHT-WIRE HARNESS CONNECTOR

Eight-wire Pigtail Harness Connector (Electronic Shift) C301

  1. Connect an ohmmeter between terminal 1 and ground . On a vehicle equipped with a Manual Transmission (M/T) , DEPRESS the clutch pedal and observe the ohmmeter. The ohmmeter should indicate a "low" resistance (less than 50 ohms) while the clutch pedal is being depressed. If vehicle is equipped with an Automatic Transmission (A/T) , shift the transmission into the "NEUTRAL" position and observe the ohmmeter. The ohmmeter should indicate a "low" resistance (less than 50 ohms) while the transmission selector lever is in the "NEUTRAL" position.
  2. Connect an ohmmeter between terminals 2 and 3 . The ohmmeter should indicate a "low" resistance (200-350 ohms) . This will check the continuity of the speed sensor that is located in the transfer case. The speed sensor picks up the rotating speed of the output shaft from two notches that are cut in opposite sides of the outer ring of the clutch housing assembly.

Checking Ohmmeter Reading For Shift Motor Position Sensor (Electronic Shift)

  1. Connect an ohmmeter between terminal 8 and terminals 4, 5, 6 and 7 , respectively. Refer to the illustration for the appropriate ohmmeter readings in each transfer case position.