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Deflation Detection System

12K views 10 replies 4 participants last post by  TurboGT 
#1 ·
Just wanted to report my experience here, since I've found information on the subject to be scarce and sometimes contradictory.

I recently swapped my OEM snowflakes to a set of 17" titanium rims wrapped in some new Blizzaks for my winter setup. I crossed my fingers that the stock TPMS sensors from the titanium would work, but I couldn't get the "deflate until horn honks" procedure to work. So instead of forking out some cash for new sensors, or disabling TPMS, I decided to take a shot at using Deflation Detection System (DDS) instead. This is the ESC sub-system that uses the wheel speed sensors (I believe) to detect when a wheel has a smaller circumference than expected and trigger the tire pressure light. I was only able to find two accounts of people trying this, one of which reported that it doesn't work, one reported that it does. So I fired up FoCCCus and changed the appropriate field from TPMS to DDS.

I'm happy to report that it works flawlessly on my 2013 FoST! I followed Ford's parameters of resetting the system in the IPC under driver assist and gave it at least 13 miles of normal driving to learn the parameters. Then I dropped one tire from 35 psi to 20 psi. Within 3 miles of driving, the IPC reported a low tire pressure and the cluster light illuminated.

This is pretty awesome. No need to fool around with which sensor went bad.

I hope this info is helpful to someone in the future.
 
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#4 ·
FoCCCus is free. I used an ELM327 cable clone.

I should also mention that I restarted the ABS module after enabling DDS in FoCCCus. This is done on the ABS tab, either using the Reset ECU or Initialize ECU (I can't remember which, but I think it was initialize) button. This cleared the low tire pressure light. I then cleared any DTCs through Forscan.

So in some of the cases I've found where people couldn't get DDS to work, I suspect it's for one of a few reasons:

1) The "learning" procedure was not executed correctly. Start this under driver assist -> Deflation Detect (hold until it says "Tire pressure stored"), then do at least 13 miles of mixed driving
2) Deflated tire scenario was not tested for long enough. It takes at least 3 miles of continuous driving, and DDS will only detect a loss of psi if it's at least 25-30% of what it was when the learning procedure was executed.
3) ABS module was not reinitialized as described above.


In the "olden days" (before reliable and affordable tire pressure sensors for direct measurement were developed), this was the first implementation of tire pressure warning systems in most cars. It is inherently less accurate than direct pressure measurement, as it relies on measuring the variance (via the ABS/TC system) in speed of each wheel over time, due to differences in rolling radius of a low inflation tire vs a normal one. Clearly there is a fairly large variance of rolling radius possible even with properly inflated tires (e.g. different tire brands; different treadwear amounts etc), so they have to allow for that in system calibration. It is low cost because all the hardware is already in place on every car. But the government mandated direct measurement systems to be implemented over time as the preferred solution.
Good/accurate info here.

In my opinion, TPMS is nice until the sensors fail or the batteries start to become marginal. In my case, I was willing to disable them (for off road use, of course) rather than figure out which one is bad, buy another one, then pay my tire shop to re-mount my blizzak. To do it right, I would do all 4, which would be an added expense. DDS has been a boon for my time and my wallet. I like this system much better, even though it's less accurate, under the "less is more" philosophy. Less parts to break/replace, and a clever way of executing a government mandate that's already dubious at best.
 
#3 ·
In the "olden days" (before reliable and affordable tire pressure sensors for direct measurement were developed), this was the first implementation of tire pressure warning systems in most cars. It is inherently less accurate than direct pressure measurement, as it relies on measuring the variance (via the ABS/TC system) in speed of each wheel over time, due to differences in rolling radius of a low inflation tire vs a normal one. Clearly there is a fairly large variance of rolling radius possible even with properly inflated tires (e.g. different tire brands; different treadwear amounts etc), so they have to allow for that in system calibration. It is low cost because all the hardware is already in place on every car. But the government mandated direct measurement systems to be implemented over time as the preferred solution.
 
#7 ·
It doesn't automatically turn off when you correct the tire pressure. The light will remain illuminated until you re-initialize the learning cycle (system information -> driver assist -> deflation detect). When I did that, the light turned off immediately.
 
#8 ·
Just a quick update for anyone searching this thread in the future. Not on the DDS functionality, as it still works flawlessly, but rather about the TPMS sensors from my 17" Titanium rims. With an Autel reader, I confirmed that the Titanium rims have 315mhz sensors, and my factory snowflakes are 433mhz. This is why I wasn't able to get the re-learn procedure to work.

This surprised me, as the rims came from a 12-14 Titanium according to the part number and design and my FoST is a 2013. I was under the impression that all pre-facelift (and maybe even 2015-17) Foci used the same TPMS sensors.

Oh well, DDS is perfectly sufficient. I might keep it active even when I return to the snowflakes in the Spring.
 
#9 ·
... With an Autel reader, I confirmed that the Titanium rims have 315mhz sensors, and my factory snowflakes are 433mhz. This is why I wasn't able to get the re-learn procedure to work...
Great info....thanks for sharing!!

Do you have an Autel TPMS reader similar to this one or did your general OBD 2 Autel reader pick up the sensor frequencies?
 
#11 ·
I'd like to chime in with my 2 cents and a cliffnotes version of what to do for anyone in the future (the information is all here, but when i was going back through it i misread a step).
1. Read bcm, then switch TPMS setting to DDS in the drop down menu (using focccus) and then click write.
2. Go to ABS module and perform module initialization (using focccus). Otherwise youll set an abs calibration fault
3. Clear codes in abs and bcm (using forscan)
4. Using you steering wheel controls go into settings and then vehicle settings where you'll find DDS. You'll highlight and click/hold "ok" to learn tire pressures. You're done!

I did this last night then drove my 30 miles to work this morning and everything is happy. I run snow tires and wheels with no sensors so this was an ideal change for me.
 
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