RX450h didn't start

[JBPRX400h]

A week last Friday we were off to France for a week's skiing holiday. Car was all loaded up during the day and we were due to leave at 19:00 in order to catch a Eurotunnel booking later in the evening.  We locked up the house, climbed in the car, seatbelts on, pressed the power button and ...... car wouldn't start!!!  All the normal dashboard warning lights lit up as usual but "ready" light didn't.  Tried several times, each time same result.

Back into house to ring Lexus Recovery who said they would try to get to us within an hour.  Meanwhile my daughter had been looking at the driver's manual to see if there was anything else we could do and found some advice on how to do an emergency start of the hybrid system.  Without foot on brake pedal press the power button to activate accessory mode, press foot on brake pedal and while keeping pedal depressed press and hold in the power button for about 15 seconds and, hey presto, ready light comes on and car is ready to go.  Tried turning car off and restarting normally a couple of times with no problem.  Rang Lexus Recovery to cancel and off we went with fingers crossed managing to just catch our shuttle.

Car performed brilliantly for the rest of the week although we were in fear and trembling every time we went to start, especially when getting off the train!

Car is booked in for Lexus to have a look on Saturday to see if there is an underlying problem.  Will report back in due course.

JBP

 

 

[rayaans]

Did you have the brake depressed whilst pressing the button?

If you don't have the brake depressed itll go automatically into accessory mode. Also, there might be a good chance the Battery in the fob might need changing.

[Ian2015]

Hi John. I have similar problem What did the garage find?

[JBPRX400h]

Hi Ian

Lexus MK tested our car when we came back from holiday and could find nothing wrong.  They did however comment that the voltage of the 12V Battery might have been a bit low at the time as I had been opening/closing/leaving doors and rear hatch open throughout the afternoon whilst loading the car.  We have had absolutely no problems since that one incident.

I did however get a cup of coffee and the car washed 

Let us know how you get on.

JBP

 

[Ian2015]

Thanks for the feedback, John. The "un-ready" issue with us is intermittent and I'm wondering as most of our trips are under 10 miles if the aux Battery isn't getting much of a charge. At least on 2nd or 3rd attempt it becomes "ready". We will keep the emergency start tip in mind for next incident. Lexus Croydon, from whom we bought, are almost 40 miles away away and to collect & return requires 3 days without a car in early June - bit of a pain but probably better than 160 miles for 2 round trips inc courtesy car or a day in the showroom drinking coffee! Thanks again. Ian

[Barry7]

I had this problem when I first owned my RX450. The car was 3 years old with 25000 on it, and the 12v Battery had failed. The car only requires this Battery to power up the hybrid system and auxilaries if this Battery is low the ready light will not come on. I removed the Battery and tested it, I then advised Lexus Sidcup and they retested it and then replaced under extended warranty.

[Chris Skelton]

Can't believe they said opening and closing doors a few times might be the cause! How much power does THAT use? Not a lot, I'd think?

It's getting so we need a trickle charger....Audi USED to have one built into their sunroof-later models abandoned this for some reason! Such a great concept.

[rayaans]

5 minutes ago, Chris Skelton said:

Can't believe they said opening and closing doors a few times might be the cause! How much power does THAT use? Not a lot, I'd think?

It's getting so we need a trickle charger....Audi USED to have one built into their sunroof-later models abandoned this for some reason! Such a great concept.

Wasn't that an optional extra? Quite expensive it was too I think about £2k or something. 

[Ian2015]

My 450 is behaving itself since my last post becoming "ready" first time, every time so have cancelled visit to Lexus. I wonder if it could have been "pilot error not pressing the brake positively enough or, more likely, the piddly aux Battery fitted as standard and short trips. I tested with an old multi-meter and found the Battery drain to be 0.2amps with everything off (car unlocked/no alarm).     According to the book this could drain a new Battery in 4 days! Maybe the 5 years old Battery is getting tired? I'll get his checked out at next service.

[fogey]

Low batteries seem to be a frequent source of problems, so you really need a very cheap but effective way of testing them. When you first open/close the car doors or open/close the bonnet all sorts of things are going on for up to several minutes later.. So if you check the Battery voltage or current it will be all over the place !

To get an accurate Battery voltage reading you need to measure it at least one hour after everything has settled. This means opening the drivers door and releasing the bonnet so you can lift it from the safety catch. (No need to fully open it until you need to access the Battery check terminals).

On the 400h this is easily done once the Battery cover is removed. I understand there is a  battery check point on the 450h, where you can connect an external charger without going directly to the Battery terminals in the boot.

So then, having released the bonnet, make sure all the doors are closed and nothing in the car is switched on ... and wait for at least one hour before fully opening the bonnet to access the Battery check terminals.

In this way I have measured an eventual standing current of around 20mA on my Rx 400h.

At this load level, the open circuit voltage of the Battery will be almost the same as the voltage measured with the car left  in the above state for one hour.

As a useful approximation, the Battery is around 25% discharged when the voltage reads 12.40 volts and even at this level it may start to lose capacity due to sulphation, if left in this state for any length of time. At 12.20 volts it is around 50% discharged and poses a significant risk of problems arising in the near future, unless it is quickly recharged.

A suitable multimeter for this is available from Maplin for under £10. Using this simple check regularly, I have kept the new replacement 12v Battery for my 400h in a good state for over 4 years now. I do not use the car much in the winter so I connect the car Battery to an intelligent charger every week the car is unused. Whilst this is connected it keeps the Battery voltage above 12.80 volts, once it is fully charged.

Hope this helps. 

[ColinBarber]

This is something that affects the 400h greatly and it was thought to be resolved on the 450h but it seems the older vehicles are now at an age where the original 12v Battery doesn't hold its charge as well is it once did and therefore leaving the vehicle for extended periods of time may result in starting issues.

[fogey]

Yes these recent posts all have a sense of deja vu about them !

The problem with the 400h battery was that it did not have the 45Ah capacity that was specified for it. It is rather difficult to measure, but you can quickly produce an estimate by seeing how quickly it discharges to a specific voltage with a given load. With the intelligent charger, a constant current is used, so if you know this current you can then time how long it takes to fully charge back again, when an LED indication is shown on the charger. I used both methods and got close agreement in the result. My "new" replacement Battery was around 15Ah ... just one third of the specified value !

These batteries are designed to have a very low self discharge, so it is not likely to be due to a long shelf storage prior to shipment. It is impossible to reject them back on the supplier as there would endless arguments about how this capacity test is performed of course.  But it is difficult for me to see how my estimate could be so far out and as it also provides a credible explanation as to why there were so many problems with the 400h 12v auxiliary batteries, I sense that my result may not be that far out. 

I guess Lexus had designed the 400h on the basis of the specified value being correct. It's a pity that they didn't do more real time tests on the actual performance of the batteries on the real market!  Perhaps the batteries they were "given" for their development tests were not  representative of those that were supplied much later, in the production run ! I expect the true story will never surface of course.

There are a lot of suspicious activities in the motor trade, as the recent scandal with VW emissions tests has revealed. Of course it is all a matter of saving as much money as possible, all at the expense of the end user, who never receives what is promised, because every effort is used to conceal the truth. 

But now it seems VW are going to have to pay for their deception and that is going to cost them billions ! 

I think the Bosch 45Ah Battery is much better from the reports of users fitting this, but apparently Lexus were not prepared to do this as they may have a fixed contract with their own suppliers. It is not surprising that many 400h owners have chosen to fit their own Bosch batteries when their existing batteries expire yet again !

So the question now of course is what is the real capacity of the 450h batteries ? 

It is specified as 60Ah, so it might actually be 20Ah with a little luck !

Well even that is 33% more than the 400h Battery ! 

So of course the answer is that you always have to manage what you are given.