Just bought a used 02 Rnage and the other day the 4x4 worked fine. It worked in both low and high. Tried it today, and nothing happens. No light on dash or noise or anything. Did a search and read some other threads, but not sure where to start. Any suggestions would be appreciated. TIA

 

Check your owner's manual for any fuses and relays that are associated with the 4x4 system (and also the GEM, which is the main 4WD "brain") and make sure they aren't blown.

See: https://www.fleet.ford.com/maintenan...ls/default.asp

 

Rockledge,
Thanks for the link to the owners manual. I don't have one, and it was nice to know which fuses and relays to check. What is this GEM you refer to and is there a way to check it? My F250 has the old manual style hubs and a floor shifter so I'm new to this electric shift.

 

Oops, sorry. Apparantly your '02 doesn't use the GEM as the 4WD brain like my '98 does.

Regarding your '02, here's how the 4x4 system works:

Transfer Case - Electronic Shift - Principles of Operation

The four-wheel drive electronic shift-on-the-fly feature electrically shifts the vehicle transfer case between 2WD, 4WD HIGH, and 4WD LOW. The system mode is selected by the operator through the mode select switch (MSS) on the instrument panel. The operator is informed which mode the system is in by two instrument cluster indicators: one for 4WD HIGH which appears as 4WD, and one for 4WD LOW, which appears as 4WD LOW. Shifts into 4WD HIGH can be made at any speed. When shifting into 4WD HIGH with the vehicle stationary, tooth blockage may occur preventing shift completion. When the vehicle is driven above 8 km/h (5 mph) the shift will complete. When shifting in or out of 4WD LOW, the four-wheel drive (4WD) control module requires that the vehicle speed be less than 5 km/h (3 mph), the brake pedal be applied, and the transmission be in NEUTRAL (automatic transmission) or the clutch pedal be depressed (manual transmission).

The gearmotor encoder assembly is mounted externally on the transfer case. It drives a rotary cam which moves the mode fork and range fork within the transfer case between the 4WD HIGH, 4WD LOW, and 2WD range positions.

The four-wheel drive (4WD) control module controls the gearmotor encoder assembly that shifts between 4WD HIGH, 4WD LOW, and 2WD modes.

Feature inputs:

- brake ON/OFF switch
- mode select switch (MSS)
- digital transmission range (TR) sensor
- vehicle speed signal transmitted from the powertrain control module (PCM) contact plate position inputs A, B, C, D

Feature outputs:

- 4WD LOW indicator (ground when activated, open circuit when deactivated)
- 4WD indicator (ground when activated, open circuit when deactivated)
- 4WD shift motor outputs

Shifts between 2WD and 4WD HIGH can be made at any speed. Listed below are the inputs and outputs needed by the 4WD control module to execute a change between any of these modes.

Feature inputs:

- vehicle speed signal
- mode select switch

Feature outputs:

- 4WD cluster indicator (ground when activated, open circuit when deactivated)

When shifting into or out of LOW range, the 4WD control module requires that the vehicle speed is less than 5 km/h (3 mph), the brake is applied, and the transmission is in NEUTRAL.

Feature inputs:

- mode select switch
- contact plate position inputs A, B, C, D
- vehicle speed signal
- brake ON/OFF switch input (battery voltage when brake is depressed, open - circuit when not activated)
- digital TR sensor (ground when transmission is in NEUTRAL, open circuit otherwise)

Feature outputs:

- 4WD shift motor outputs
- 4WD LOW cluster indicator (ground when activated, open circuit when deactivated)

Inspection and Verification

Visually inspect the following for obvious signs of mechanical and electrical damage.

- 4WD control module
- Wiring harness
- Mode select switch (MSS)
- gearmotor encoder assembly
- Connector(s)
- Circuitry

- Battery junction box (BJB) fuses:
1 (50A)
3 (50A)
13 (20A)
30 (10A)

- Central junction box (CJB) fuses:
28 (7.5A) (manual transmission)
10 (7.5A)
11 (7.5A)
5 (15A)

 

Is the 4wd control module the deal by the brake lines mounted under the hood on the left side that is kind of round and says 4x4 on it. If so is there any way to test it, and do they just quit working suddenly?

 

The 4WD control module on your '02 is located inside the cab, behind the passenger side kick panel.

There isn't any way to really test the module itself. It does however, store trouble codes that are 4WD specific. Unfortunately, a fairly sophisticated scanner is needed to pull the codes from the 4WD control module.