username:

So the light on mom's car came on this afternoon, I've never seen it before until looked it up. Just curious what the RX330 (04 fwd) uses to monitor the tire pressure? It didn't look like it had a TPMS from the outside.

Kendig

Prior to 07, the RX Tire Pressure Monitoring System (TPMS) is software-based and does not use direct measurement. All 4 wheel hubs have speed sensors on them which are part of the Anti-Lock Braking system. Software-based TPMS's monitor the speed of all 4 wheels. An underinflated tire has an effective circumference that is just a little less than a properly inflated tire, and as a result rotates slightly faster. This difference in speed is what sets off the tpms.

By the way, you can't always tell if a car has direct TPMS from the outside. Here's a site that sells replacement sensors and retrofit systems. Vehicles listed as having retrofit systems available do not have direct-measurement tpms. http://revolutionsupply.com/TPMS/AppGuide.aspx

jfelbab

I believe in the 04, it doesn't measure actual pressure. I think it measures tire rotational speed differences. Later models have real TPMS.

username:

Ah ic. So is there some sort of sensor on the inside of the wheel or something?

Kendig

Precisely. To make Anti-lock Brakes (ABS) work, one of the many little computers in the car needs to know that 1 or more wheels have stopped turning (e.g. are "locked up") while 1 or more others are still turning. So, to implement ABS, every wheel hub (not the wheel itself) contains a sensor which sends pulses as the wheel rotates. This is typically a magnet (or magnets) on the hub or axle, and a sensor that triggers each time a magnet passes it. When the ABS computer detects both pulses and no-pulses, it starts its high-speed pumping of the brakes.

Somebody realized that with the sensors already in place, another little computer (or the same one) could also listen to the pulses to detect speed differences resulting from a low tire. Easy quick and dirty solution. However, individual sensors in each wheel have the advantage of seeing the individual exact pressures. The freshening of the RX330 to the RX350 for 07 appears to have included the "real" tpms.

mandyfig

The sensor can be seen on top of the caliper.

ChrisV

iTrader: (1)

This is exactly what I would like to ask the forum. Someone in here is selling a set of wheels off his 09 RX350 Pebble Beach Edition. Do you think it would work on my 04 RX330? The sizes between the 2 models are the same. What I am wondering about is the TPMS, how do I know if my 04 model has this feature (Pictures would be greatly helpful) and if I install the Pebble Beach Edition wheels would the TPMS light comes on? Isn't this simply just a swap or something I have to look out for? I'll verify with the dealer on this just to be on a safe side. THanks.

RA080623

You can use the 09 wheels on your 04 without any issues. I picked up some 08 wheels and put them on my 04RX. As mentioned above, the 04 uses rotational analyses to tell you if the tire is under inflated - not the sensor. Personally - I would take the TPMS out of each wheel and sell them. Might be able to pick up $100 or so against the cost of your new rims... mind you - you have to pay to get them off.

Scottydog

Are the new TPMS sensors part of the valve stem? I would assume it would be an easy matter to remove them.

benzo555

iTrader: (11)

Yes they are. You can always replace them with the traditional rubber stems from the non-tpms cars.

tromly

That's a great question , as Ive often wondered what would happen if I switched wheels. I too love the Pebble Beach wheels and have seen them on EBAY, now I know I can bid with confidence.

diverchris

Looking for a little help myself. I have a 2005 rx330 AWD. I want to get an additional set of rims and tires for winter. Can anyone tell me if, or what, part number I need for the tire pressure monitor system. Or is the sensor on the hub, or brake caliper.
Thanks

mmlex1987

So, I need to know. Do all 2004 RX 330 vehicles have a TPMS system, even if in this year it was based on rotational speed vs. actual tire pressure? If so, it goes to show that you can till learn something new all the time!!

RXSF

Chris, I believe since you own a 2005 model, you do not have direct tire pressre monitor and therefore there is no sensor or you to get.

and Mike, all 2004s had the TPMS system standard even though as we said before it is not direct.

mmlex1987

Thanks RXSF for the info, I wish it was that simple when trying to find out if I had AFS after all of these years, when I really thought I had all/or at least most of the available options.