Jeep Cherokee AW4 Transmission Override PDF Instructions Manual

Background:
The transmission override frees up the computer’s control of first and second gear in the AW4 automatic transmission found in Jeep Cherokees from 1988 to 2001 as well as the 1993 Grand Cherokee. The engineers at Aisin Warner decided that Jeep owners did not need manual control over the first two gears in their transmission. They designed the transmission to have a “1-2” slot in the shifter to control both first and second gear with the computer. Therefore, the user does not have any control when the transmission shifts to second or first. For example, the transmission does not allow engine braking in first gear because the computer refuses to shift into first. Additionally, the computer shifts into second after about 4500 rpm, a detrimental effect in sand and snow. A user mod has been out for quite some time to free up these gears. However, with the
integration of the OBD2 system in 1997, the check engine light will trip when this mod is used. The MAF transmission override is designed to be compatible with OBD2 systems and will not trip the light.

What to expect from this device:
The transmission override has three positions, D, 2, and 1. “D” position: In the “D” position, the override has no effect and the transmission shifts normally. “2” Position: In the “2” position the transmission is forced into second gear, it will not shift into any other gear. In this position the vehicle will even start in second gear. Due to the design of the transmission hydraulics, engine braking in this position has the following features. When the override is in the “2” position the shifter is in the “D” position, the transmission will not provide engine braking. When the throttle is removed, the transmission goes into a freewheeling mode offering little resistance. This freewheeling mode is beneficial, it prevents the wheels from locking up if the transmission accidentally is forced into second with the override during high speeds. Another benefit is that the vehicle will not immediately start to slow when the throttle is removed, but maintains the response of second gear. To engage engine braking, shift the lever into the “3” or “1-2” position. In these positions, the hydraulics in the transmission allows engine braking in second gear. “1” Position: The “1” position operates in a similar fashion to the “2” position. The transmission will be forced into first gear, it will not shift into any other gear. While the shift lever is in either the “D” or “3” position the transmission will not provide engine braking. The transmission will freewheel when the throttle is removed. To engage engine braking, the shift lever must be put into the “1-2” position.

Instructions:
1) Remove the dash panels.
a) Start by removing the lower panel below the steering wheel. It is held on by screws on the bottom and clips on the top.
b) Remove the metal backing to this panel. It is screwed on from the top.
c) Remove the trim around the radio and climate controls. There are no screws in this panel, remove by gently prying around the edges starting from the bottom.
d) Remove the steering wheel cowl. There are screws on the bottom. Removal makes removing the upper dash easier.
e) Finally, remove the upper dash panel. This is the piece of dash around the instrument cluster and radio. It is attached with several screws and clips. The headlight switch must be pulled through this panel. It is a tight fit, but possible.
2) Drill the mounting holes in the dash for the switch using the template in the back of this manual. Figure 1 shows the best location to mount the switch. Use the existing decretive trim as a guide for centering the holes.
NOTE: Several Jeep owners use this location on the dash to mount other accessories and switches. Obviously this is not the only location possible for the Transmission Override. It can be mounted anywhere in the vehicle where there is room. The center console next to the shifter is a good alternative.
3) Install the switch plate onto the dash using the supplied #4 nuts, bolts, and lock washers. Bolt the switch onto the switch plate using the supplied nut and a 10mm wrench. Attach the knob and knob cover, correctly aligning the indicator to the letters.
4) Locate the Transmission Control Unit (TCU) using figure 2. The TCU is located under the steering wheel near the middle of the vehicle next to the gas pedal..
5) Clean the top of TCU and use the supplied tape to attach the Override Module to the TCU. See figure 3.
6) Unplug the factory connector from the TCU and plug the connector into the Override Module. Connect the Module’s Plug into the TCU. Figure 3 shows the TCU plugged into the Module.
7) Run the control wires from the Module to the switch’s future location in the dash.
Route the yellow control wire to the wiring harness connected to the back of the radio. This yellow wire is for override illumination.
Splice the yellow wire into the illumination wire in the wiring harness. In most cases the illumination wire is a black wire with a yellow stripe. If an aftermarket radio is used, refer to the radio’s users manual.
9) Connect the control wire to the Override Switch observing proper polarity.