E39 Lastik Basınç Monitörü Uygulaması |
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E39 İÇİN LASTİK BASINÇ MONİTÖRÜ UYGULAMASI BWM used two different types of tire pressure monitoring systems the Tire Pressure Control (RDC) system, and the Tire Defect Indicator (RPA) system (formerly know as the “DWS” system). The RDC system uses pressure and temperature sensors installed in each wheel as part of the valve stem. The sensors transmit their individual tire data to antennas mounted in each wheel well that feed to the RDC controller. This system is technologically superior, because it can alert you to absolute pressure changes (like when all four wheels decrease pressure over time), it is more sensitive to slight changes, and it can react faster. The disadvantage to the RDC system is that it puts a few ounces of extra weight in each wheel, and the system is more expensive and labor-intensive to retrofit. The RPA system uses the speed pulses from the ABS controller to calculate their relative rolling diameters. The advantage of this system is that it is passive (does not add “stuff” to your wheels and lots of extra wiring) and less expensive and easier to retrofit. It’s down side is that it is not as sensitive to pressure changes. BMW introduced the RDC system in the E38, and they may have used it in the E65/E66. However, the RPA system is clearly BMW’s preference, because they switched to the RPA system for all other models. I much prefer the RPA system too, since I do not want the weight and complexity of a sensor spinning mindlessly in each wheel. The RPA is better suited to a high performance vehicle, and I suspect that BMW has similar priorities, since they dropped their absolute pressure system for the ABS wheel speed version. According to the BMW WDS, the RDC system will detect about 5 PSI pressure change. The RPA system will detect pressure drops of about 30% (roughly 10 PSI, depending on tire pressure). I selected the E39 M5 RPA system for my retrofit. Overall, the installation is very straightforward, almost as if BMW had intended for us to retrofit a system like this. The M5 RPA controller module has the identical dimensions as E38 RPA module, so it even snaps into its proper place behind the glove box. Nearly all of the wiring splice points for this project are also located in the white plastic “module holder” in which the RPA controller is located. The only exceptions are the ground splice point, the switch illumination splice point, and the right rear wheel speed signal. These are the parts that I purchased for the installation: E38 RPA RETROFIT PARTS
These are the wiring diagrams that I used for reference. The DWS system was used in the later E38 model years, so these came from the E38 wiring. The same system was also used in other modules, so you could look there as well. DWS SWITCH WIRING DIAGRAM These are the connection points for the module and the switch.
SWITCH
The first and most important step: DISCONNECT THE BATTERY! You will be fishing around a lot of wiring and sensitive components. If you accidentally shorted something along the way, it could really ruin your day. The project took roughly 4 hours, but most of the time was just spent locating and double-checking the tap points. If I did it again, I could probably finish in under 2 hours. Also, I did a fair amount of preparation work studying the WDS and creating my own installation instructions. If you undertake this project, I do recommend that you have the WDS on hand, since the location of the right rear wheel speed signal can be in different locations, depending on car model and date of manufacture. Most of the pictures that follow came from the WDS. I only added a few to clarify locations or add detail. The first picture is actually of the completed installation, but it also shows where the splice points and the DWS module are located. This view is from the floor of the passenger side foot well, looking up and behind the glove box. The DWS module is the black box with the blue plug. The splice block mentioned above is immediately to the left of the DWS module in this picture—it is where the large bundle of wires leads. DWS MODULE LOCATION AND SPLICE POINTS The right wheel speed signal is the big challenge. It is available in the area near DWS module, but it feeds into the 84-pin ABS controller, so I was not totally confident that I would tap the right wire. The signal also leads to the engine DME controller, so I decided that was the safest place to find it. The only challenge of getting a wire to the DME, is that I had feed it through the firewall somewhere. As it turned out, this was very easy. There is a rubber pass-through about 1” in diameter that angles down and feeds into the electronics box under the hood. I just pushed a wire through until I had about 18” through. Then I found it in the electronics box and fished it up with a bent coat hanger. The destination for the Right Rear tap point connector X60004 on the engine DME, as shown in this picture. ENGINE DME LOCATION AND CONNECTOR PLUG The pass through is located just above the carpet, against the firewall, in the passenger foot well. This picture shows me pushing a green wire through the passage that came out under the hood. FEEDING THE RIGHT REAR WHEEL SPEED WIRE In this picture, you can see the coat hanger reaching down underneath the DME module and pulling up the wire I pushed through from the interior. FISHING THE WIRE UP TO THE DME The hardest work was tapping into the “official” ground splice point for the DWS module. This is located on the bottom of the passenger foot well, underneath the carpet. The carpet and backing are freakishly thick and stiff, so it took a great deal of strength to pull it back so that I could actually reach this splice point. I did mine officially, but I recommend that you ground the module somewhere else. The effort simply was not worth it. GROUND SPLICE POINT LOCATION Next, I ran wires from the passenger foot well area to the driver foot well area for the DWS initialization switch. The switch has three pins, two lead to the DWS module, and one taps into the interior lighting splice point, so that the switch will illuminate when you turn on the lights. The 2nd hardest part of the project was reaching the illumination splice point. This is located right next to the steering column. The space is not large enough for two hands, and it was a very uncomfortable reach. So, after a lot of fumbling and retries, I got the tap installed. INTERIOR ILLUMINATION SPLICE POINT LOCATION After I ran all of the extension wires (ground splice, Right Rear tap, and DWS switch wires), I made a mini harness. The mini harness had 9 wires, 5 with spice connectors and 4 that I left longer for butt splices into my extension wires. I had someone else call-out the connections and I snapped-in the pins to help cross check my work. I also labeled everything with a piece of scotch tape so that I could again double check when I snapped it in place. DWS MINI HARNESS Finally, after I slide the splices and butt-joined the loose wires, I reconnected my car battery. It worked perfectly on the first try. When I pushed and held the button for 6 seconds, I got the Set Pressure message telling me that the car is ready to initialize itself to the current tire pressure. Then I drove it a bit to give it some miles to calibrate. To test it, I dropped one of the rear wheels by 20 PSI (down to 20 PSI) and drove it a bit more. I got the tire defect message in less than ½ mile. Very cool! SET PRESSURE MESSAGE TIRE DEFECT MESSAGE |
