Jeep JK Wrangler
Rubicon Locker Modifications, Hacks, Cheats
Ideas on how to use the factory Rubicon lockers in 2wd
and 4hi |
tech
|
We have received
many questions from readers regarding the operation of the JK Rubicon lockers in 2 wheel drive and 4 wheel drive high
range. The new JK is very dependent on it's computer
system and the locker work around is not nearly as simple as
a hot wire. Most methods involve "fooling" the
computer into "thinking" one thing or a form of hot-wiring.
Evidently the JK
computer is very integrated and will see through the hack by
seeing the Jeep is moving at a higher speed than is possible
in low range (The JK will re-engage the front sway bar and
disengage the lockers at speeds greater than 18 mph). Excess
speed may cause the computer to generate
error codes, perhaps causing warranty implications or cause
the Jeep to behave erratically.
The TJ
style switch modification will not work since the instrument
cluster and all of the driver controls and switches
communicate with the computer using the CANbus system.
Use these
modifications at your own risk! See our thoughts on
these mods below.
We have compiled
from various internet sources methods and ideas of getting
around the JK locker operation.
F-f-f-foolin method -
This allows you to use the
lockers
in all transfer case positions and should allow
the sway bar disconnect to operate as well.
It will also allow the ESP to operate in all
three modes. With this option the ECM will
simply think the transfer case is always in 4
low.
Background: The Totally Integrated Power Module
(TIPM) provides sensor ground to the transfer
case and many other components. This is on pin
28 of connector C1. The transfer case switch
then returns a MODE SENSOR SIGNAL back to the
TIPM on pin 3 of connector C1 (Yellow/Light
Green). This signal varies in resistance as
follows:
Operating Mode
Versus Resistance SENSOR POSITION OPERATING MODE
SENSOR RESISTANCE (ohms)
Position/mode/ohms
1/2H/1124-1243
2/4H/650-719
3/NEUTRAL/389-431
4/4L/199-221
5/NOT USED/57-64
During normal
vehicle operation, the Powertrain Control Module
(PCM) monitors the transfer case position sensor
return voltage to determine the operating mode
of the transfer case. Refer to the Operating
Mode Versus Resistance table for the correct
resistance (1-6) for each position.
So if one simply
connects this return signal to ground, which is
the equivalent of 0 ohms, causes the TIPM to
assume the transfer case is in 4 low. A
good modification would be to install a SPDT
switch to connect the signal return circuit
through a 220 ohm resistor to ground.
Description of the Transfer Case Position Sensor
from the Factory Service Manual:
The transfer
case position sensor is an electronic device
whose output can be interpreted to indicate the
transfer case's current operating mode. The
sensor consists of a five position, resistive
multiplexed circuit which returns a specific
resistance value to the Powertrain Control
Module (PCM) for each transfer case operating
mode. The sensor is located on the top of the
transfer case, just left of the transfer case
centerline and rides against the sector plate
roostercomb. The PCM supplies 5VDC (+/- 0.5V) to
the sensor and monitors the return voltage to
determine the sector plate, and therefore the
transfer case, position.
There are two wires going
to this sensor. One is Yellow with a Light
Green stripe and goes to pin 1 on the connector.
This is the wire you want to connect to ground
with a new switch. The other is Dark Blue with a
Yellow stripe and goes to pin 2 on the
connector. This wire should show +5 volts with
the ignition turned on.
TIPM
location: The TIPM is located in a plastic box
directly in front of the battery. See
illustration.
This modification
will still cause the lockers and sway bar to
return to normal mode after reaching speeds
greater than 18 mph.
Consideration: The
problem with the above method is that the
following things act different in 4 low:
Speedometer, ABS, transmission shifting,
throttle pedal gain (sensitivity), target engine
idle plus a few others. There are
tell-tales that were designed to detect a
malfunctioning transfer case range selector.
If you do this, the FCM and I believe CCN will
set a DTC. Your dealer WILL be able to see
it when you service the Jeep. Probably bad for
your warranty.
Consideration: Some
have reported doing this mod with no problems
and no codes even after a dealer visit. |
Most sources say the
above method is most reliable and least invasive.
| Total Locker Control
-
This allows complete
control over each locker independently. It is a
simple modification as well. It is reported that
the locker indicators on the dash will simply
blink whenever you use this modification. The
computer may also set a trouble code but this
has not been confirmed. This modification
is based on this wiring diagram:
click for a
larger image
To control the rear
locker you simply need to ground pin 42 of C1
from the TIPM (violet/light green). To control
the front locker you simply need to ground pin
41 of C1 from the TIPM (violet/dark blue).
Like in the other
above method the FCM monitors it's locker relay
output for any unspecified draw or source. The
FCM will set a DTC or a tell-tale in this event
as well. Your dealer WILL be able to see it when
you service the Jeep. Probably bad for your
warranty.
Consideration:
This method may not be subject to the 18 mph
speed limit. Locker operation will
continue until switched off.
Consideration:
There may be problems with the lockers on and
the ESP system in full effect. The ESP
monitors steering position, wheel speed, etc.
When you would make a corner with the rear
locker on both wheels will maintain the same
speed. The ESP may misinterpret this as a
wheel with loss of traction and cause the system
to try to compensate using throttle control and
ABS. |
A few thoughts...perhaps it's
not really needed to have the use of the lockers in 2WD or
4WD HI. The JK makes very effective use of the
electronic traction control especially in rain and snow
conditions. Why not just go to 4 LOW if the conditions
require locker use? Poking around the complex
electronic system that makes the JK is risky and can be
costly. It is our opinion to leave everything alone.
Credit to JDRogers, este,
jkforum, and Don-a-Vee |
