sparta3993

Bought a very reasonably priced set of used 18s for my 250. Owner gave a great deal as the age of the tmps was unknown. I’m assuming the tmps are from 06 as the tires are the Dunlop sp sport Maxx which was the oem tire for these 18s?!?!?! (Rims look very clean, inside and out, so almost willing to bet tires were never changed).
Anyway I thought I knew what I was doing.

My current 18s, tires, and tmps (in black) were programmed to “my car”.....
The 18s, tires, and tpms (in red) were not programmed to my car.... so it was safe to say the tmps sensor would trip.... right?

I mounted the red set, head down to fountain tire so they can reprogram them. I left one of the black 225 as a spare just in case these old tires gave out..... the tpms light didn’t turn on??? Fountain tire tells me my drivers fronts sensor needed to be replaced... okay great Kal tire said the same thing even though we deflated my passenger rear to trip the sensor...... what gives? So after 50 miles of driving, playing what the initial, main, and 2nd, 1 mile away from home the tmps light came on. All my tires have the pressure...

Called lexus service and the service tech said “if they are the same style rims there is a good chance the Lexus computers reading the tpms in the red set.

now I’m parked in the garage... black set stacked in front of my bumper. Red set on the car, with the tmps light on now....

Not only did I hate tmps to start with, but why did they have to make the system so freaking complicated?

any idea why it didn’t trip the sensor with the red set? And why it got tripped as soon as I arrived to my street?

Htony

TPMS has built in battery which has definite life span. Did they trigger/scan the TPMS? Good TPMS should give out id. PSI, temperature, state of battery.
Since already one is gone dead, remaining 3 TPMS life span is in question. If I were you, I'd replace them all at this time.TPMS sleeps, when car is in motion
it wakes up and signal is sent to TPMS receivers. That is why you need trigger/scan tool to work on them. I use Autel TPMS tool and Tech stream when working
with them.

sparta3993

Thanks for that info but my focus is on the warning light. Tires were scanned that’s how I know the ones low battery...... since the battery was low they never programmed the red set to the car so I’m wondering why the black set that was already programmed and working, is not showing a warning light?

“why did the sensor not trip when the red set was mounted on the car...... why did it take 50 miles to trip? Most importantly why did the warning light not turn off after I parked the car in the garage with the black set sitting in front of the car?”

Htony

Have you register the new TPMS into the ECU? Installing it does not do anything until you make the ECU relearn them.

lovekeiiy

You have to reprogram the TPMS anytime you disconnect the battery and change the tires. I had that issue with I got my car and Lexus changed the front tires. Light went on ten minutes down the road.

jr4div2

The TPMS warning light is not immediate. It takes some time and averaging for it to decide if the pressure is in our out of spec. Apparently it just took the 50 miles to realize it lost contact with the black set. As far as the black set sitting in front of the car and the light not going off, again it takes time and driving for the light to change state.

sparta3993

Thank you!!! Someone actually read what I was asking! So that makes perfect sense, but I’m wondering why it took so long to come on. Because with the black set if I lose a little air, or a battery is dead. The lights on within 20 seconds of ignition.

so seeing nothing’s been “relearned” mouting the already programmed black set should turn off the light after a while??!?!? Or have I throughly confused the ecu?

jr4div2

Mount the black set and drive around. The light should go off. Go get the TPMS sensors replaced in your red set at a good tire place and they should be able to program them into the ECU. Also, you can keep two sets programmed and switch them with the <0> buttons to the left of the steering wheel. This allows for a summer set and a winter set, but you could have one for your black set and red set whichever you wish.

sparta3993

Thanks for everyones help. Again my concern was why the TPMS light was not tripped right off the bat. I threw the Black set back on and without even driving the light turned off.

I know exactly how TPMS "should" work, though not when the system is acting funny.

The black set makes perfect sense. mount 3 blacks and 1 red, lights on.... Mount all black, lights off. Drop the pressure in one of the blacks, light goes on....
The red set makes no sense. TPMS light is off no matter what you do..................

And just for everyones sake I bought a new set of TPMS for the red set and installed them all today. Programmed them to the car, check. Drove around, check. Dropped the air in two tires to 15psi, check. TPMS lights still off, check..... what????? how the hell? So go back throw all the black sets on, check. Drive about 5 miles down the road to my buddies house (we erased the black set so the TPMS light is currently on). When we get there we reprogram the black set again. TPMS turned off without moving the car, check. Drop the pressure in one of the tires to 30 psi and the TPMS light comes on, check.......

Lexus allowed me to return the sensors, so I bought some Toyota ones with he same results. For the heck of it I threw the Toyota TPMS into my Tacomas winters... Oh wow they worked?

THIS MAKES NO SENSE

I don't know how to dumb it down more then that. Lexus says its because the rims were programmed to the same generation and model?!?!?! still makes no sense?

lovekeiiy

Sounds like it's not your sensors but whatever they give their readings to.

sparta3993

The senssors have a fcc code right? I’m wondering if the fcc Id maters if my 2IS module is a us spec and the sensors in the red set are Canadian fcc?

thoughts?

Htony

Canada does not have FCC. It's equivalent is Industry Canada comm, branch. id. has different formats. Some with leading zeros, some not., Most NA cars run on 300MHz band. For some reason your TPMS seensor is not recognized by ECU, you got a wrong set. When you scan the the sensor with a trigger/scan tool, you can see what they are readily. id. is in Hexa-decimal format. I use TPMS trigger/scan tool for seasonal tire/rim swap. Trigger and scan, connect the tool to OBD port
execute relearn command, it is done. Very handy tool.

Htony

Your car is still remembering and reading the older sensors. What ia such a trouble? The order of triggering/scanning using tool is LF >> RF >> RR >> LR and spare tire if it has TPMS. Just SIMPLY what is the result of scan of those sensors which will give id, pressure, temperature. Because your car still reads older set of TPMS, sure it won't give you alarm. As you drive away from your garage, at some distance car will lose signal from the sensors, it'll give warning indicator "check tire pressures". That is what happens with my '15 RX hybrid. Think logic. I am in Calgary. If you are personally interested, using tech stream read the TPMS ids in the ECU which will confirm the ids. are that of old set. Some TPMS sensor needs magnet to trigger. From which vehicle did the red set come from? I believe red sets are not registered into ECU. IMO, the red sets batteries are marginal, their operation is unreliable. Some mechanics have near zero basic electronics knowledge. Find a competent one. BTW, I am retired EE, often I have to help them out with electronics problems. Some of them don't even know which way current/electron flows in a diode or transistor. Younger new generation mechanics are better to deal with.

sparta3993

red set came off a 2is. And I agree the battery is low. Though the thing that’s bothering me is why it took 50 miles for the TPMS light to trip. Why not as soon as the older tires were out of range. Why did the new sensors not work on my 2is but they worked on my Tacoma?!?!?!?

Htony

You said battery is low, in cold weather, battery gets lower in output. Sounds like your TPMS are in marginal condition, IMO.