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Tire Pressure Monitor Systems

Description Installing on other models Overhead console removal
TPMS parts Retraining the sensors Monitor system test
New AutoPump system for 2004 models



Tire pressure display
    
Tire pressure display


The Tire Pressure Monitor System was a new safety and convenience feature that premiered in the 2002 model year. It was offered as an option on all WJ models except the Laredo Sport. The system is capable of displaying actual tire pressure levels for all four tires and the spare, is accurate to within +/- 1 PSI under all conditions, unaffected by uneven loading or trailering, unaffected by slippery road conditions, and able to monitor tire pressure while the vehicle is at rest. A new advanced system, with an automatic tire pump, will be introduced during the 2004 model year.

The Electronic Vehicle Information Center (EVIC) in the overhead console monitors the wireless tire pressure signals from the five tire sensors and determines if any tire has gone below the low pressure threshold or raised above the high pressure threshold, as shown in the table below. A warning is only sounded when a particular tire, any tire, goes above or below the thresholds. These thresholds are preset by the factory and are not changeable.



Low tire pressure thresholds High tire pressure thresholds
System status indicator Tire Pressure System status indicator Tire Pressure
On 26 PSI On 45 PSI
Off 31 PSI Off 40 PSI


On the "Low" side, the warning will chime when a tire drops down to 26 PSI, and the display will read "Low Pressure". On the "High" side, the warning will chime when a tire pressure exceeds 45 PSI, and the display will read "High Pressure". The warning message displays for three seconds and then switches to the tire pressure "trip" screen. The particular tire that is low and caused the message will blink at one second intervals on the display. The blinking will continue for the rest of the ignition cycle OR until an EVIC button is pressed. If the display is removed without correcting the condition, the warning will reappear (without the chime) in 60 seconds. If a tire becomes low while the vehicle has been off, the warning signal will appear on the display about 8-10 seconds after the ignition is turned on.

Each of the vehicle's five wheels have a valve stem with a pressure sensor and radio transmitter built in. Signals from the tire pressure sensors are received and interpreted by the EVIC. A sensor in a mounted wheel will broadcast its detected pressure once per minute when the vehicle is moving faster than 25 mph. The spare tire sensor will broadcast once every hour. Each sensor's broadcast is uniquely coded so that the EVIC can determine location. The individual tire pressures can be displayed graphically on the EVIC. Each tire transmitter is battery powered. The battery life is projected to last 7-10 years under normal operating conditions.

If the spare is moved and mounted on the vehicle, the display will chime and display for five seconds the message "Spare swap detected". So how does the system know the spare has been switched? The spare tire transmitter is programmed to send a signal hourly. Any and all mounted wheels, when spinning above 25 MPH, will transmit their signal every minute. The system will detect that the tire previously programmed as the spare was put on the vehicle when the signal from that tire changes from hourly to every minute.

The system identifies the location of the four mounted tires by way of a simple initial training process. The EVIC is put into a programming mode while a magnet is momentarily placed, in sequence, on each of the valve stems. A signal is sent back that identifies the LF/RF/LR/RR tire locations as well as the spare. This is an easy process that can be done by anyone, and is explained in detail below.

The valve stem transmitters can be easily installed into any wheels that fit the WJ's, whether factory or aftermarket. The spare can also be mounted atop the vehicle and still be reconized as such by the system. As well, a set of additional transmitters can be purchased to install into a set of different tires for those owners who often change their wheels and tires for off-roading.





In addition to the frequencies shown in the picture, if a tire loses more than 1.5 psi of pressure the signal will be sent every five seconds.





INSTALLING THE FACTORY TPMS ON OTHER WJ MODELS

The upgrade can be accomplished in 3 easy steps:

1. Replace EVIC module (module only, you do not have to swap-out the entire console)
2. Replace existing valve stems with the TPMS stems/sensors (4 tires plus spare)
3. "Train" system (for recognition of each tire location on vehicle)

This option can be added to all model years of WJ vehicles, although it can be rather expensive if the parts are purchased new from a dealer. The EVIC module inside the console must be replaced with the advanced version than includes the TPMS circuitry. There is no extra wiring, the existing module is simply removed and replaced with the new one. Most EVIC modules are interchangeable. If you have the standard EVIC, for example, you can upgrade and install either of the two step-up models. One adds HomeLink, and the other adds HomeLink plus the TPMS. The old module can be sold if desired to slightly offset some of the upgrade costs.


There are 3 different style modules produced for the WJ, as shown in the chart below:


EVIC modules
Type 1999-2000 2001 2002-2003
Basic 56042273AC 56042745AA 56042754AF
With Homelink 56042271AD 56042749AA 56042749AF
With TPMS -- -- 56042756AF





REMOVING THE OVERHEAD CONSOLE


Overhead console removal

To remove the EVIC module you need to detach the overhead console. The console is held in place with one phillips head screw and two spring clips. The screw is located near the windshield side, and should be removed with a non-magnetic screwdriver as to avoid interference with the compass. Next, grab the console from the sides, wedging your fingers underneath it, and carefully and firmly pull it straight down.



EVIC module removal
EVIC module front
The EVIC module is attached to the console with four screws. Click to enlarge.


The EVIC module, shown from the back and the front in the photos above, is attached to the console with 4 phillips screws. There is one small wire harness to unplug, located near the back of the module. After the new module is installed, the compass zone info may have to be re-entered into the EVIC. Note that the new EVIC module does not come with the front lens, you'll need to pull that off of your old unit and install it in the new one, a very easy process.



Tire pressure sensor module

Tire pressure sensor module.
   
tire pressure sensor location

Inside view of installed sensor.


The 5 sensors are then installed into the tires of the new vehicle. The Factory Service Manual details exact instructions and cautions for mounting the sensors. The system must then be retrained with the special magnet so that the EVIC learns the specific location of each transmitter. Training directions are shown below.



tire pressure module  location

Tire pressure sensor installation detail.




Tire Pressure Monitor System parts:

Part name: "EVIC module"
(without lens)
Quantity: 1Part number: 56042 749AFList price: $ 475.00 ea.
Part name: "EVIC lens"
(not needed if old one is re-used)
Quantity: 1Part number: 05012 882AAList price: $ 14.00 ea.
Part name: "Valve/Transmitter"Quantity: 5Part number: 52088 990AC List price: $ 55.00 ea.
Part name: "Valve stem nuts"Quantity: 5Part number: 52088 961AAList price: $ 2.93 ea.
Part name: "Magnet"
(Miller special tool)
Quantity: 1Part number: Miller 8821List price: $ 22.00 ea.
(Prices listed are for reference purposes only and may vary by dealer. Parts are not available from this web site.)






RETRAINING THE TIRE SENSORS:

The sensor transmitters can easily be retrained by anyone and takes just a couple of minutes.

1. On the overhead console, use the "Menu" button to advance to the "Retrain" option in the EVIC menu.

2. When "Yes" is selected, training will begin, starting with the left front tire.

3. Place the special magnet (Miller tool # 8821) momentarily on each valve stem, one at a time, in clockwise order (LF,RF,LR,RR,SP). You'll have 60 seconds to place the magnet on the first tire stem and 30 seconds for each of the other four, the spare being last. As each tire location is "learned", there is a confirming horn chirp. That's it, the correct tire pressure will now be displayed for the corresponding tires.

The special magnet tool used for retraining is included with those vehicles in which the factory has installed the TPMS option. The magnet can also be purchased for around $25, otherwise a pair of 6" or so speakers with good size magnets will do the trick.


Tire pressure re-lear magnet

Tire pressure sensor re-learn magnet
   
Tire pressure re-lear magnet

Placement location for retraining





TIRE PRESSURE SYSTEM TEST


TPMS test mode


The following test can be used to verify two functions. One, that the tire pressure sensors are transmitting properly and two, the EVIC module is receiving these transmissions accordingly. Using the STEP button on the overhead console, scroll to the blank display, then press the RESET button for five seconds, a beep will sound indicating the start of this test. The vehicle icon and transmission counters will now be displayed, (same display as individual tire pressure except counters replace tire pressure values).

Upon entering the test mode, the EVIC will clear the sensor counter and each time a sensor signal for a road tire is received, the EVIC will update the counter value (according to the service manual, the vehicle must be driven at 25+ mph to transmit, however, the vehicle I tested counted with the vehicle parked and ignition on). The counter values should all read the same value. If any of the road tires indicate a different value than another tire sensor, this is a sign of a problem. Replace the appropriate tire sensor and retest the system. This test will continue until any of the overhead console buttons are pressed or the ignition is turned off.

Further technical, diagnostic and safety information can be found in both the Factory Service and Body Diagnostics Manuals.





valve stem/transmitter

Close-up of TPMS readout.



EVIC circuit board

EVIC module board with TPMS circuitry.






New SmarTire / Cycloid AutoPump system

A tire pump inside each wheel cap!


AutoPump tire system

Inertia compressor pump, internal circuit board, and pump shown mounted inside wheel cap.


DC will likely introduce a new advanced tire pressure monitor system from SmarTire for the 2004 model year. In conjunction with an automatic tire AutoPump made by Cycloid, the combined system automatically and continously re-inflates tire pressure to a specified level, ensuring optimal inflation of tires under different situations and temperatures.
The inertia compressor is only 1" thick by 3" in diameter and weights a mere 8 ounces. Its expected design life is 130,000 miles, with ten years of battery power. The system will be shown at auto shows in the U.S. starting October 2002, installed in the Grand Cherokee Concierge prototype concept car.





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