Forum Staff Member
TRS 20th Anniversary
- Aug 19, 2001
- Reaction score
- So. Calif (SFV)
- Vehicle Year
- Make / Model
- Bronco II
- Engine Type
- 2.9 V6
- Engine Size
- 2.9L V6
- 2WD / 4WD
- Tire Size
Chris1044 said:I wrote this because 1) It made The specifics of this apply to a 94 Ranger with a BW1354 case, but I’m sure that the basic concepts can be applied to other years.
I can’t cover every practical situation that you’ll encounter with the 4x4 not working. This is written to be a guide for most situations……its going to be long, and assumes that you can 1) use a test light to check fuses and 2) use a volt meter to check for power/grounds/resistance in different circuits. Also, I will stress that you DO NOT JAM A TEST LIGHT / THICK VOLT METER LEADS INTO ANY CONNECTOR. YOU WILL RUIN THAT CONNECTOR or ruin its ability to maintain a solid connection with the other pin. Don’t do this ever on any connector period. Go to Wally world, go to the sewing dept. and pick up a pack of small T-pins – they work great for this sort of thing or back probing connectors.
If you can’t use a volt meter, you can still do some basics – just don’t expect to find something like a corroded wire at some connection that’s causing your 4x4 system failure.
I also can’t be held responsible for stupid on your part. If you jack only your front two tires up, put the truck in 4x4, and try to see if the front wheels are spinning….you get my point….
First, are you sure that you’ve got no 4x4? This article is going to cover the electrical shifting system, and will not touch on your 4x4 hubs and how to fix them.
Before you get in over your head, and realize you’ve got shitty hubs and not a bad 4x4 shift system, do yourself a favor and put the truck up on jack stands (all 4 tires off the ground). Shift the truck into 4x4, and with the motor running put the trans into drive. Let out on the brake, and let the truck idle in drive…..check to see if both drive shafts are turning. If they are, yet you’ve got no front wheels spinning, you’ve got a hub issue. If one is spinning it’s because you’ve got an open diff……
Assuming that your front drive shaft is not spinning, you’ve got a 4x4 engagement problem…….now you’ve got to do some diag
1. Check to make sure all fuses for the system are good. There are two fuses that supply power to your 4x4 shift system – one located under the hood, the other under the dash. The under fuse is a 20 amp maxi fuse, the under dash fuse is a 15 amp ATO fuse – on the 94 rangers its located in the fuse position 7.
a. If they’re good, go to the next step,
b. If they’re bad, you’ve got a short somewhere in the system. Try to replace the fuse, and see what happens. If it blows, you’ve got something shorted to ground in the circuit. If you know how to use a volt meter, you should know how to find a short in the circuit, and will need a wiring diagram to do so.
2. If all the fuses are good, the next step is to run the 4x4 module self diagnostic. The 4x4 module is located behind the driver’s side rear jump seat on super-cab models, but as far as the other locations I don’t really know. This module will have three connectors going to it – one will be a pig tail, the other two will be located on the right side of it (side towards the front of the truck). These two connectors must be removed to diagnose the module. With the key in the off position, remove these two connectors from the module. Next, turn the key on with the engine off. On top of the module is a white rectangular button located next to a red LED….push the button and watch the LED.
a. If it flashes, this indicates the module is working properly. Go to the next step
b. If it lights up and stays on, it indicates that the module is likely bad. If nothing happens it means the module is either bad, or has no ground/power. In either of these instances power and ground should be verified before scrapping a 4x4 module.
i. The 4x4 module receives its power/ground through the 8 pin pigtail connector.
1. Pin Position 1 = Open, no wire
2. Position 2 = Solid Black = Ground
3. Position 3 = Orange/Black = Logic Ground
4. Position 4 = Orange = Transfer Case Motor Control (Clockwise) 2H-4H-4L
5. Position 5 (across from position 4) = Yellow = Transfer Case Motor Control (Counterclockwise) 4L-4H-2H
6. Position 6 = Brown = Electromagnetic Clutch (Feed)
7. Position 7 = White/Purple = Ignition Run and Crank (Start) Feed (Fused)
8. Position 8 = Dark Green/Light Green = 20A Maxi-Fuse in Power Network Box (under hood fuse)
3. With the two connectors still unplugged from the module, the next step is to verify the 4x4 dash switch input. Take the 5 wire connector, the one with the grey connector color, and check the following:
a. Connect an ohmmeter between terminals 1 (White/Light blue wire) and 2 (Dark Blue wire). Then depress the 4x4 (2H-4H) switch. The ohmmeter should indicate a low resistance value (less than 50 ohms) while the switch is being depressed. If this occurs, the switch feed to and from the module is good
b. Connect an ohmmeter between terminals 1 and 3 (orange/light blue wire). Then depress the LOW RANGE switch. The ohmmeter should indicate a low resistance value (less than 50 ohms) while the switch is being depressed. Again, if this occurs, the 4 low switch is good.
c. Connect a test lead between terminal 4 (brown/white wire) and ground. Turn the ignition switch to RUN and observe the indicator lights. The LOW RANGE light in the instrument panel and LOW RANGE indicator light on the switch should illuminate. This indicates the 4x4 lo switch/dash lights are good
d. Connect a test lead between terminal number 5 (grey wire) and ground. Turn the ignition switch to RUN and observe the indicator lights. The 4x4 light in the instrument panel and 4x4 light on the switch should illuminate. This indicates the 4x4 hi lights/dash lights are good.
e. If any of these tests fail, you will have to check the wires from the module to the back of the switch for continuity. This is done easily by removing the dash switch and connecting an ohmmeter between the same color wires, with one lead at the module and the other at the switch. A resistance value of 10 ohms or less is good, any more indicates excessive circuit resistance. If all 5 wires have low resistance between the switch and module, the switch is bad and must be replaced.
4. The next step will check the circuitry to the shift motor. Your shift motor must be hooked up for this to work. Grab the 8 wire connector that is unplugged from the 4x4 module. It will be tan in color. Check the following:
a. Connect an ohmmeter between terminal 1 (red/light blue for manual trans vehicles, red/white for auto trans vehicles) and ground. On a vehicle equipped with a manual transmission, 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 the vehicle is equipped with an automatic transmission, shift the transmission into NEUTRAL 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. This ensures that the Park/Neutral switch or Clutch pedal switch is good (needed for 4 lo shifts)
b. Connect an ohmmeter between terminals 2 (light green) and 3 (light blue). The ohmmeter should indicate a low resistance reading (235-470 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 transfer case rear output shaft from two notches that are cut in opposite sides of the outer ring of the clutch housing.
c. Connect an ohmmeter between terminal 8 (yellow/white) and terminals 4 (violet), 5 (white), 6 (brown/white) and 7 (orange/white), respectively. Refer to the following chart for the appropriate ohmmeter readings in each transfer case position.
OHMMETER READINGS FOR SHIFT MOTOR POSITION SENSOR
Pin 8 Y/W To: TRANSFER CASE MOTOR POSITION
2 High Edge 1 2H-4H Edge 2 4 High Edge 3 4H-4L Edge 4 4 Low
P/Y Short Short Short Short Open Open Open Short Short
W Open Open Open Open Open Short Short Short Short
BR/W Short Short Open Short Short Short Short Short Open
O/W Open Short Short Short Short Short Open Open Open
NOTE: Edge positions and Mid-Shift positions are valid motor codes that the module will respond to; however, any motor found in one of these positions should be replaced/torn apart and cleaned/inspected to prevent the overshooting of shift points.
SHORT is a "low" resistance reading on the ohmmeter (zero ohms).
OPEN is a "high" resistance reading on the ohmmeter (infinity).