Useless TPMS?

[suss6052]

Originally Posted by jsr72

Isn't that true only for indirect systems?

Technically from version 5 of the 12 owners guide pg. 245:

As an added safety feature, your vehicle has been equipped with a tire pressure monitoring system (TPMS) that illuminates a low tire pressure
telltale when one or more of your tires is significantly under-inflated.
Accordingly, when the low tire pressure telltale illuminates, you should
stop and check your tires as soon as possible, and inflate them to the
proper pressure. Driving on a significantly under-inflated tire causes the
tire to overheat and can lead to tire failure. Under-inflation also reduces
fuel efficiency and tire tread life, and may affect the vehicle’s handling
and stopping ability.
Please note that the TPMS is not a substitute for proper tire
maintenance, and it is the driver’s responsibility to maintain correct tire
pressure, even if under-inflation has not reached the level to trigger
illumination of the TPMS low tire pressure telltale.
Your vehicle has also been equipped with a TPMS malfunction indicator
to indicate when the system is not operating properly. The TPMS
malfunction indicator is combined with the low tire pressure telltale.
When the system detects a malfunction, the telltale will flash for
approximately one minute and then remain continuously illuminated.
This sequence will continue upon subsequent vehicle start-ups as long as
the malfunction exists

Basically its only meant to show a gross under inflation but otherwise you're supposed to pay attention. Its really only a legal cya for the manufacturers mandated by the government.

As long as it doesn't tell you the actual pressures its pretty much useless for monitoring anything except a catastrophic failure.

[jsr72]

Originally Posted by suss6052

Basically its only meant to show a gross under inflation but otherwise you're supposed to pay attention. Its really only a legal cya for the manufacturers mandated by the government.

That's not what I was asking, it was the comment about not being able to detect when all four tires are low at the same pressure.

Direct systems measure the actual pressure for each tire, not pressure differentials between tires.

[suss6052]

Originally Posted by jsr72

That's not what I was asking, it was the comment about not being able to detect when all four tires are low at the same pressure.

Direct systems measure the actual pressure for each tire, not pressure differentials between tires.

Since it did not seem to sound the alarm when all the tires were equally low it seems that its still only caring about the pressure differential unless its low enough per the O.P.'s case. All four tires were exactly at the same pressure initially which was way low, but they said there was no alert from the system which you would think it would be if it actually knew enough to report which tire/ sensor had which pressure. Currently the system does not appear to be capable of displaying this information.

Ergo if it cared about absolute pressure being low on one or more tires at the same time should have gone off with them all equally too low, but that's not what it did.

That could be indicative of a failure in programming or an RF interference however as it should have gone off, but others have also reported that either with new sensors that weren't programmed, or without sensors sometimes it still takes a long long time for it to error out.

Does seem to be a malfunctioning system per the service manual, but not like Ford would actually fix anything at all ever.

TPMS Function

The TPMS system monitors tire pressure using 4 valve stem mounted TPMS sensors, these sensors transmit tire pressure data to the BCM. The TPMS sensor locations and unique identifiers are trained (calibrated) to the BCM based on the training order. The BCM compares the tire pressure data sent by the sensors with a programmed desired tire pressure. This programmed pressure is the same pressure indicated on the VC label. If the tire pressure deviates from the programmed tire pressure the BCM, using the Medium Speed Controller Area Network (MS-CAN), signals the IPC to illuminate the TPMS warning indicator and to also display a message on the message center. The programmed desired tire pressure cannot be changed.

The scan tool is a useful tool in diagnosing TPMS concerns and may be used to verify the accuracy of the tire pressure data transmitted by the TPMS sensors. This is accomplished by comparing the BCM tire pressure Parameter Identification (PID) data to the actual tire pressure using a digital tire pressure gauge. Training the sensors is not necessary after a tire rotation on vehicles with the same front and rear tire pressures however, the BCM cannot recognize that the sensor identifiers have been moved to different positions and will retain the original position information for each sensor.

Wheel Rotation and Sensor Training Techniques

Training known good sensors from another vehicle cannot differentiate between a faulted module and Radio Frequency Interference (RFI), as some noise source could be preventing the module from receiving the tire pressure status from the original sensors as well as the known good sensors. This technique can be used to differentiate between a sensor and a module concern. If the module in the suspect vehicle cannot train any of the sensors on the vehicle and, likewise, cannot train known good sensors from another vehicle, then the concern is with the module or Radio Frequency Interference (RFI) and not with the original sensors. The original sensors should not be replaced. If a sensor in a certain location has caused several events, yet the sensor trains and seems to operate normally, moving that particular wheel to a different location on the vehicle is a good way to isolate the concern to a certain sensor/wheel location. Rotate the wheels and road test the vehicle. This can be done in an attempt to replicate the concern and help determine if the concern followed the sensor or remained in the original sensor location. If the vehicle has been stationary for more than 30 minutes, the sensors go into a "sleep mode" to conserve battery power and they will need to be "woken up" so they transmit the latest tire pressure information to the BCM.
Refer to: Tire Pressure Monitoring System (TPMS) Sensor Activation (204-04B Tire Pressure Monitoring System (TPMS), General Procedures).


Training Sensors in a Different Order

If the first sensor fails the TPMS training procedure, the BCM aborts the entire procedure. Starting the training procedure at a different wheel is a technique that can be used to determine if the remaining sensors can train to the module. This can help save time determining if one sensor is damaged, other sensors are having concerns or the BCM is experiencing training difficulties with a certain TPMS sensor location.

TPMS Warning Indicator

The TPMS warning indicator and vehicle message center occasionally displays faults that cannot be resolved by the customer. Treat these messages as TPMS faults that must be serviced.

TPMS Warning Indicator Illuminates Continuously

The TPMS warning indicator remains on continuously and the message center displays LOW TIRE PRESSURE when any of the tire pressures fall below the low pressure limit. When this condition exists, adjust the tire pressure to the recommended cold tire pressure indicated on the VC label.

Tire Pressure Monitoring System (TPMS) Warning Indicator Flashes

The TPMS warning indicator flashes for 70 seconds and then remains on continuously when the ignition is set to ON and the TPMS is malfunctioning. The Parameter Identification (PID) TP_STAT can be used to determine why the TPMS warning indicator is flashing.

Tire Pressure Sensor Fault — The message center displays TIRE PRESSURE SENSOR FAULT when a TPMS sensor is malfunctioning.
No communication with the BCM — The TPMS warning indicator illuminates when the IPC has not received any signals from the BCM for more than 5 seconds. The message center displays TIRE PRESSURE MONITOR FAULT.
Tire Pressure Monitor Fault — The message center displays TIRE PRESSURE MONITOR FAULT when the TPMS is malfunctioning

[Kabigon]

Originally Posted by SaToX

I appreciate your input, its letting me know that their are inconsistencies between cars on the TPMS being triggered. Hopefully we can get a few more people to check their cars and we can get this resolved.

How do you factor in all of the tolerances involved?

For example, if the dealer said that the tires were at 28 PSI, does it mean that all four tires had an exact pressure of 28.000 PSI?

[copernicium112]

Originally Posted by aaron.b

Well I've got 1000 miles on my snow tires and no warning yet. Copper icum..... R u sure they didn't remove your sensors? To me it looks like they auto program

No, the sensors are still there. Where do you park at night though, relative to where you keep your tires? It is a proximity thing. One of the sales guys at my dealership got his Focus a week after mine last year (even though he ordered a week before me, he was pissed when mine showed up and he didn't have his yet). He got winters but didn't bother with the sensors. He also keeps his summers in the garage where he parks every night. I asked him if he ran into any problems and he said he didn't at first but outside of work an minor errands, he was always back in his garage every evening. When he took his family out of state to visit some relatives for the holidays they drove for the day, stayed in a hotel, and the next morning when he went out to continue on, his warning came on.

I have a small garage (I don't even park in it, I park in front of it) so I keep my extra set of tires in the shed in the back corner of my yard, away from where I park. I'm running back to dealership on Saturday so I'll confirm either way but as others have said, if they self-program why do they sell the tool to reset them (and why did they have to reset them the last two times they swapped my tires)?

[pozi240]

Well, Ford is correct, you do NOT need to "retrain" new sensors to your car.. They do "auto train" or whatever you want to call it. All three of our Fords have the TPMS system (all, including our F150 use the valve stem style), and we have seperate winter rims and tires for all (we live in a heavy snow belt area, winter tires are a must). We bought our winter rim/sensor combo from the dealer, but, I assure you, in the last three seasons, I've switched over my own rims each season in my garage and the dash display resets within 500m of driving (less than a minute). No visit to the dealer needed, ever. I don't know where this rumor started about having to "train" new sensors, etc. I will say that my neighbor has a couple of Honda's and a Dodge truck, and he says that he has to have the sensors trained, so, they must use a different system. I know his CRV uses the "band style" sensors which are expensive and a pain to install.
Also, another thing to note, since some have brought it up here, the trick of just putting a summer rim/tire in the back of your car, etc. To turn out the warning in your dash, that will only work if you keep the wheel moving once and a while, since, the sensors will go to "sleep" after so many minutes of not moving (preserves battery life). Just saying.

[SaToX]

Looking at the NHTSA there seems to be conflicting info. One spot it states that the system should indicate when any tire including all four drops 25%. In another spot on the site it seems to be referencing a table that states 20 psi is the safety floor. Although it does state

"Overall, we feel that the 25 percent threshold adequately captures the circumstances at which low tire pressure becomes a safety issue. We also believe that this level would be acceptable to most drivers and would not be considered a nuisance to the point that it would be ignored by large numbers of drivers. We also believe there is no reason to examine higher thresholds (e.g.,� a 30 percent threshold), which would provide fewer benefits for similar costs"

http://www.nhtsa.gov/cars/rules/ruli...part1-2.html#1

[darkangelism]

on the 18s it seems to go off if one tire reaches 28 lbs

[SaToX]

Originally Posted by darkangelism

on the 18s it seems to go off if one tire reaches 28 lbs

What is the recommended tire pressure in the door ?

[bawxcar]

Tell me this, if you have a tire sensor telling you that there's low pressure in a tire, you're going to keep driving without physically getting out to look at it? I know I'd get out and make a judgement call on it and inspect the other tires to make sure it's only one. It's a good idea to have the reset tool, but ford also does it for free. Meh