In Australia, Mitsubishi chose not to add TPMS (Tyre Pressure Monitoring System) to our versions. Many other manufacturers here do include it as a feature. So, I was acquainting myself with my partners fathers new CX-3 and read about the TPMS of that car. It doesn't use the pressure monitors set in each wheel. Instead it uses the wheel speed data from from the electronics in each wheel bay to calculate the speed in relation to the wheel circumference. The owners manual lists how to reset the TPMS if a tire/tyre is replaced or the pressures are changed.
As all new vehicles, the EC especially, have sensors in each wheel bay for ABS and stability control etc. The sensors measure the speed of each wheel and calculates if it has wheel spin or some other handling problem. Using the data the SAWC system adjusts the throttle and wheel braking to compensate for any instability. It is also used by the ABS system.
I did a search and came upon a TPMS system that uses this data by connecting a bypass plug to the OBD (On Board Diagnostic) port which is a standard port across the industry for connecting diagnostic tools for service and maintenance. Here is the RHD OBD port which is located by the drivers left knee in the centre console:
The LHD port is underneath the knee airbag and more accessible. The RHD version is stuck behind the lower climate control outlets.
So the kit I found was on AliExpress and consists of the OBD bypassed cable, a TPMS display and its associated connection cable from the OBD bypass. They also give you a spudger tool to pop open the trims. Beats using you fingers. There is also a small set of instructions through most of it relates to the timers for fatigue and service reminders and their setup.
I chose to install the display in the centre console next to the ECO switch so it was easily visible.
Routing the cable for the display was quite simple once I had removed the climate control outlets and controls from the centre console.
Once I replaced the console I headed down under the dash and removed the lower dash cover to get access to the wiring loom.
The next thing I did was to remove the power from the car by removing the negative terminal. When you have your head under this area you are right next to the drivers knee airbag and you don't want that going off near you head and face.
Now back under the dash I took note of the orientation of the OBD plug in its mount. It has a lock clip as you look at it and the replacement by the bypass OBD needs to be the same otherwise anyone connecting to the OBD port later will be unable to unlock the clip as the other side is flush to the trim panel.
The task is to unclip the OBD port and move it out of the way so you can plug the female end of the bypass to it and then insert the male end of the bypass back into the mount connected to the console so the port is still available for service access later.
Disconnecting the port clips was as simple as inserting flat tip screws driver up the sides of the connector to disengage the locking tabs. The issue was getting the port out from behind the two climate control lower air outlets which are screwed to the side of the climate control module. The easiest way I found, without dismantling the bottom dash was to remove the panel to the left of the steering wheel where there is a single point for a switch but it is currently blanked out. One screw at the bottom of the panel and four claw clips and it was free.
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Next I removed the two bolts which attached the left side the drivers knee airbag to the dash subframe and this allowed me access to the ODB connector which was now free of its clips. I simply pushed the ducts to one side and pushed the port out into free space behind the dash. Next I connected the bypass cable to the OBD port and pushed the male end of the bypass back into the slot vacated by the original OBD port. This was a little tight and tricky but teasing with the tip of a flat tip screw driver got it into place and the lock tabs on the connector clicked nicely into the mount on the console.
Last step was to close up all the panels and reconnect the battery. Once the car was started (without issue) the display for the TPMS came on.
The final installation step was to check and adjust the cold tire/tyre pressures to those in the owners manual. Calibration is a simple task. On a stretch of straight road, at least 1Km long, press and hold the L button until a tone plays and the display goes blank. Now simply, and safely, move into the traffic flow and drive for at least 1Km without exceeding 70Kph. Once the system has senesed the wheel speed data it sets the display to 2.4 for all four wheels. The display is indicative only and doesn't show the actual pressure. 2.4 is nominal, 1.8 is low and 2.6 is over pressure.
The small instruction set shows how to set sensitivity of the TPMS for the percentage of air/pressure loss. You can also set a reminder for service interval and rest stops but the EC has both built in to the car so they are superfluous really.
All in all the system is snap to install and get up and running. I will be interested to see whether the bypass cable causes any issues with the Mitsubishi diagnostic tools at the next service visit. Being a passthrough cable which simply leaches data from the ECU feeds I don't see any issue considering everything seems to be working as normal. Time will be the judge.
