Tire Warning Indicator Light

[Fran D]

I've searched this forum and haven't found a direct answer to my question. I have an '01 Windstar where the Tire Pressure Warning Indicator will light up after some random period of driving. All of the tires are the same size and at the same pressure, so I am guessing that this is due to an intermittent problem with one of the ABS sensors (is that a valid assumption?). However, a visual inspection of all the ABS sensors predictably shows no trouble (i.e., cables and connectors are good, tone rings and sensors heads aren't very dirty, there isn't any oil/brake fluid, etc. all over them, etc.).

My question is, when the Warning Indicator is lit, does the Powertrain controller log which ABS sensor has reported the failure? I'd rather use a scanner to interrogate the controller rather than start changing all of the sensors. If I'm heading in the wrong direction, feel free to steer back on course.

Thanks in advance.

[LeSabre97mint]

Fran

First off, welcome to AF's! There are a lot of good people here that are willing to help out.

How many miles on your 01? Is the ABS functioning? (no ABS light) Do you have rear brake shoes or disks?

Regards

Dan

[Fran D]

Originally Posted by LeSabre97mint

Fran

First off, welcome to AF's! There are a lot of good people here that are willing to help out.

How many miles on your 01? Is the ABS functioning? (no ABS light) Do you have rear brake shoes or disks?

Regards

Dan

Thanks for the welcome. I've already been able to solve my cruise control problem (the infamous Brake Pressure Switch!) by searching this forum!

Now, to answer your questions:

1. Mileage is 100K.
2. ABS is functioning (no ABS light). I also tested by panic stopping and I could feel the pulsations.
3. Rear drum brakes.

Any ideas?

[LeSabre97mint]

Fran

Your rear sensors may require cleaning. They are magnetic and attract the dust from the shoes. They may be clean enough for the ABS but not functioning for the tire psi. This is just a guess....

Dan

[Fran D]

Dan,

I'll give it another look. They did appear to be clean enough and I did try to wipe down what I could see with a rag. I'll try to go in there again with some brake cleaner and see if I can freshen it up better.

By the way, do you know the answer to my original question? Whether the PCM logs which sensor provides the warning for the tire indicator?

Thanks for the help!

Fran

[phil-l]

I believe this is the first Windstar tire pressure warning system question I've seen on this forum (or any other, for that matter), so we're all still learning.

So... I did some quick Googling - and came up with this:

http://www.nhtsa.dot.gov/cars/rules/...eprmonsys.html

...which claims that indirect tire pressure monitoring systems that use the ABS sensors *can't* identify which tire is under-inflated (and specifically noted that the Windstar, among other vehicles, has this type of system). The article discusses how the systems work, and helps explain what the systems can determine - and what they can't.

Fran D: So the short answer to your question appears to be "No". Sadly, this doesn't help track down the problem when the system claims a tire is underinflated, but all tire pressures check out.

[Fran D]

Originally Posted by phil-l

...So the short answer to your question appears to be "No". Sadly, this doesn't help track down the problem when the system claims a tire is underinflated, but all tire pressures check out.

Lovely. Thanks.

[phil-l]

I am kind of curious about this problem. A tire inflation warning - without a real tire problem - would seem to indicate an ABS sensor problem. But an ABS sensor problem of any significance should also generate an ABS error code.

My only conclusion from this thought: There's a subtle ABS sensor problem that is just enough to throw off the tire pressure monitoring system - but not enough to trigger an ABS error code.

Anyone else have ideas?

[road_rascal]

About the Tire Pressure Warning Light: on my '01 it will light up when the tires get really hot from highway driving (hot summer days on the interstate). I usually run pressures at 36 psi. When the warning light goes off the tires are around 44 psi hot. I don't consider this to be a malfunction, just an anomaly, as this has only happened a few times.