mw430

My trip to Lexus was a real surprise. They reported that all TPMS sensors were working (transmitting) correctly and had correct battery voltages. All after 17 years! So, as they had to do nothing they charged nothing!

I've given in and booked it into Lexus ext week for all TPMS sensors to be changed for £410. I was driven to this because there is so little written on older SC430s sensors that I could feel reliant upon. Was it a US or UK car and what was its age, and add to that the masses of other Lexus car types owners with TPMS problems (or successes) and I just couldn't sort the wheat out from the chaff!

If I replace a battery in a sensor I suppose I'm not changing any of the sensor's characteristics...apart from maybe making it work. If this is correct I should be able to keep away from Lexus software and costs. Does anyone know if this is the case, please?

I don't drive the car much but the TPMS has always alerted me to pressure loss while it's been sitting in the garage for months. So I suppose I have relied on the sensors and I would feel a bit susceptible without them. My current idea is to change the batteries as it doesn't look too daunting on youtube but there's still the unknown that bugs me. When do sensors, or the car, need "reprogramming" for want of a better expression? Most comments online say this is what's needed, but when? Is it for physically new coloured sensors, is it for new batteries, is it just for later models that use the same sensor in each wheel, or what? I feel inclined to replace the front two sensors batteries and take pot luck. I can't see I'd have lost anything apart from time. After 16 years all the batteries are probably on their last legs and Lexus prices make me feel I am too!

After the front tyres were replaced the tyre warning light came on, flashing with a repeated bleep. There had been no problem before. They couldn't investigate as their TPMS detector only worked with later sensors which used a higher frequency. Because of this they said all the sensors were dead! I arranged with Lexus to check this fault out and the day I was due there the tyre light didn't come on. Nothing. So I cancelled. Two days later a solid tyre light was on. All the wheels were at the same pressure, 2.5 bar, so I upped each a little. No change. 50 miles later the solid light was still on, so probably not a tyre pressure problem. I know, as the car's from 2005, that light's ignored on the MOT. At least it is now but things can change. So I have to decide, hopefully with others' experience, what I should do. The car's records up to 2009 when I bought it, show nothing at all concerning sensors so their batteries could be 15 years old and on their last legs. Can these sensors' batteries be changed? The sensors are colour coded. Can this type simply be replaced by the same colours and that's the end of the job, leaving the car to do the learning or is any programming needed? Not ignoring the need for someone to loosen off and refit the tyres if I did change the sensors myself.! I know this topic's been around a long time but from the web it's often hard to tell if the cars posts describe cars from the UK or US and if the sensors are coloured or not. For example, is the removal of the two plugs beneath the centre console woodwork a fix for all the sensor types and does that extinguish the flat tyre light? Doing that would give me a chance to fix things later if regulations changed and would cost me a lot less right now. Any help would be welcomed!

I guess the final thing, which I found really surprising, was that when I began to charge the battery from its 7.7V state, its charging current went to what I'd expect from a near fully charged state in just over an hour. This reminded me that that's very similar to what happened when I started charging the Toyota battery after it droped to 10.7 V. I can't work out why that should happen so I must admit to not understanding car batteries. My investigation's over and I'll have to rely on a new battery.

Yesterday the Cavalier battery read 12.4V. Today it read 7.7V. It's been connected as the Toyota battery replacement for 3 weeks and nothing on the car's been touched. It was left unlocked with no alarm and no doors have been opened. The Toyota battery did much the same thing in a third of the time, so maybe it is the car doing it. I haven't done a controlled drainage test yet as what's happened makes that seem irrelevant. I really don't see the next step except to buy another battery and see how that behaves.

Yes. I did mean 50 mW. Thanks. I had started the engine twice before I started the last tests to try to shock off any coatings the plates might have...and after that the voltage was above 13V. It had been over 14 V before that. I'll use a tyre compressor as a load as you suggest. It takes 10 A and we'll see what the result is. Then I'll check it with a 50 mA drain.

Now I have tested the 2 batteries for 6 days I'm no closer to finding out anything useful. The disconnected Toyota battery measured 13.81/13.31/13.3/13.27/13.25/13.23 V over the 6 days and the old, connected, Cavalier battery measured 12.69/12.5/12.47/12.41/12.37/12.33 V. Neither set of results is surprising and nothing, to my mind, indicates either battery is defective, or is this a wrong assumption? Next I'll rig up a 5mW load while the Toyota battery is still disconnected and check again...a 220 ohm or thereabouts resistor should do.

I can't believe that after 5 days something switches on and drains the battery, but with this car I shouldn't discount anything. I just can't think of what I can do to detect when, and if, the "normal" drain of 50mA suddenly ramps up, if it does! Where is the alarm battery and what type is it? If I disconnect the battery when it's charged the alarm sounds so, at that point, its battery may well be charged too. I have a smaller spare battery that's in perfect condition, taken off a car that needed more oomph. It's kept its 12.7 volts for many months. Changing the Toyota one for that one it'd be interesting to see what happens over a week or so starting from fully charged. The Toyota one's only done 6000 miles and II accept it could have aged with lack of use but I'm baffled as to what can happen inside the battery at a roughly specific time to drop the voltage by effectively one cell! An inability to retain charge was the reason I bought a new battery in the first place, but I never tested the drain so the battery might have been in poor condition. However the new one only took a few months to behave like the old one. With all the reports of this not being unexpected in an SC430 I saved myself the hassle and didn't make a claim...I just lived with it. Now I'm intrigued.

I carried on testing the battery and came p with something that was a complete surprise. Each day I checked the voltage and it measured, each day from the day after charging, 13.1, 12.95, 12.89, 12.68 and then 10.4 V! In case I'd done something to make this happen I repeated the tests. They were, 13.13, 12.95, 12.85, 12.77 and then 10.7 V. Can anyone help me understand what's happening, please?

...and despite this minimal current drain the battery went flat in 5 days! So, it looks like the intelligent charger must be connected all the time. Unbelievable for such an expensive car.

My 2005 SC has always suffered from battery drain but it's taken me a decade to get down and test where the current's going. Initially I bought a new Toyota battery. In those days the car was used a few days a week and the battery failed to start the car about every 2 weeks. So for years I charged it, and all through lockdown I used an intelligent charger. The car was never used except to go to the garage for its MOT. Now the battery is flat after 3 or 4 days and, having tested it I am no closer to solving what causes the problem. Remote locked or unlocked the drain starts at 850 mA, quickly drops to 125 mA and then settles down to 40 mA, enough for a 1/2 Watt led. No wonder no-one's come up with a definitive solution!

The SC430 failed the MOT because of a leaking front shock absorber and, after replacing that, Lexus reported the nsf tyre was badly worn on the outer edge. The nsf camber is 2.5 degrees and the osf 0.5 degrees so the nsf looks like it's way out! I see that the camber adjustment can be done with the cam bolt in the lower arm but there's also a vertical bolt, 90109-14009, which is also called a camber adjuster, fitted to the suspension a bit higher up. It looks like a bolt threaded at both ends so does anyone know what it does and how it's supposed to do it?

Finally I exchanged the sensor for a Denso and everything's back to normal. There's a bar on the socket opposite the side that mounts to the car. That locks on a protrusion on the plug that's between two guides. It needed a flat head screwdriver a bit narrower than the width of the bar so that when the screwdriver was turned it forced the bar out and released the plug. I guess anyone that's done an O2 sensor replacement probably knows this but it was all new to me. I was able to see the plug/socket detail using my Snake Scope, but getting used to the reversed image took an hour! The heater was open circuit. The new sensor's waveform has the same amplitude as the other bank's forward sensor. Basically all 4 sensors have the same max and min so maybe they could all be good for quite a while longer. The only noticeable difference in performance with the change was tickover. With the faulty sensor the revs stayed at 1100rpm for a very long time. The new sensor's tickover drops to 800rpm or less in 20 seconds. Thanks to everyone for their comments and for the sunny weather!