2006 RX400h Won't Go Into 'P' Unless Selector Held Forward

[ntl]

Hi,

As the title says, I can only get 'P' to light on the dash if I hold the selector as far forward as it will go - the moment I let go of it, 'P' disappears and the car is in some sort of limbo mode where nothing is selected. This means I can't leave it in park, and I have to hold it foward to be able to start it; not sure how long that will last before I'm unable to select it at all.

Backstory: I just replaced the 12V Battery after it went flat three times in a row to the point of being unable to unlock remotely. A couple of days before I replaced it, it took 10 mins to get it into 'P' to start the car, nearly stranding me. I didn't seem like even holding the selector forward would get 'P' to light up, so after replacing the Battery it seems like the behaviour has changed slightly, but who knows. I also had a few moments where 'D' and 'R' were problematic before the Battery replacement, but that seems to be gone now too. Can't say for certain though.

[Herbie]

May be a silly question but I think the lights are only indicators - what does the actual transmission do?

[ntl]

Good question. I'll see if it wants to roll when physically in the park position, although it still refuses to go into 'Ready' mode unless 'P' is lit when I turn the key.

[ntl]

9 hours ago, Herbie said:

May be a silly question but I think the lights are only indicators - what does the actual transmission do?

I went out to check the car again and measured the voltage at the 12V Battery terminals as 11.82V. It's a rubbish B&Q multimeter so not sure how accurate that was, but I figured it may come in handy for relative measurements to see if the new Battery is being drained like the old one.

To answer your question, after that I was able to start the car by holding the selector all the way forward while I turned the gear, and was then able to shift into drive and reverse and move the car. I got a new error on the nav screen and I wish I had recorded it - I think it was something about about the P position and it also warned of how the Battery wouldn't charge in neutral.

After moving through the gears a few times, I turned the car off and back on again and this time it would go into 'P' every time without me having to hold it?! I still don't trust it, but I wonder if something has somehow reset/recalibrated. Putting it in park engaged the parking brake as expected.

Finally, I turned off the car and measured the voltage at the Battery again - this time it had jumped up to 12.5V. I don't know if that is significant, but I wasn't expecting such a big jump considering the Battery is brand new and had even been topped to 100% before installation. I wish I had measured the voltage when it was installed this morning, but I'd borrowed the multimeter this evening. I'll be checking the voltage every day without using the car to see how it's holding up and welcome any other checks I can do.

[Herbie]

If the Battery voltage is dropping quickly then it sounds like you have a parasitic drain somewhere, so these may help:

 

 

[ntl]

Thanks for the table. I think it must be draining 

I just checked it again 15 hours later and it was down to 11.35V - a brand new AGM Battery. According to the table - and if the multimeter is to be trusted - it's almost drained the Battery completely in this time. The locks, motorised accessories and gear selector worked perfectly, however.

I started the car again and the voltage across the terminals was well over 14V while the hybrid system charged the Battery, then once I turned it off I measured it dropping from 12.26 to 12.13 over the course of a few minutes - I could see it dropping.

I think I'll pull and charge the Battery to 100% to get a baseline on this meter.

[ntl]

Oh, something else I noticed was that the sunroof wouldn't operate automatically - I had to hold the switch down and release at just the right time to get it to seal (overshooting starts to open it via the tilt mechanism). Before all this started, I could press and let go and it would automatically stop at the perfect position.

[ntl]

9 hours ago, Herbie said:

 

That's a great video, by the way!

[ntl]

The Battery finally charged and its voltage is 13.20, so something must be draining it heavily...

[Herbie]

1 hour ago, ntl said:

The battery finally charged and its voltage is 13.20, so something must be draining it heavily...

Time for that multimeter to earn its keep then. Good luck.

[Barmac]

Sunroof issue sounds like it needs a reset after Battery going flat? When I've had discharged Battery on our 400h, I've seen an error message on dash asking for “P” to be selected prior to starting even though P is already selected. Seems very much like a discharged Battery. All you need to do now is find out why!

[ntl]

On 1/26/2023 at 7:50 PM, Herbie said:

Time for that multimeter to earn its keep then. Good luck.

I ended up taking it to a Lexus specialist! However, they've yet to find the cause of the drain which is apparently around 1 amp, so I'm starting to get a little worried. Especially after scrapping our last car due to electrical issues that couldn't be diagnosed...

On 1/26/2023 at 9:45 PM, Barmac said:

Sunroof issue sounds like it needs a reset after battery going flat? When I've had discharged battery on our 400h, I've seen an error message on dash asking for “P” to be selected prior to starting even though P is already selected. Seems very much like a discharged battery. All you need to do now is find out why!

Yeah, that was it exactly! It seems that I need to calibrate the sunroof and passenger window every time it goes flat. I had no problems with the gear selector after a one hour drive last week, so could be voltage related. However, I have noticed on occasion that the selector is like stirring porridge, so there could be a mechanical element to the issue too.

[Herbie]

2 hours ago, ntl said:

I ended up taking it to a Lexus specialist! However, they've yet to find the cause of the drain which is apparently around 1 amp,

I sincerely wish you good luck and I hope they find the problem quickly for you.

I have to say though, if it had been me, I would have gone to a proper auto electrician because they are a trade/specialist in their own field. Mechanic for mechanical issues, body shop for body work, electrician for electrical work. I doubt very much that Lexus will have their own specialist auto electrician on staff; I can't imagine them having enough work to employ a guy for 37.5 hours/week.

[ntl]

39 minutes ago, Herbie said:

I sincerely wish you good luck and I hope they find the problem quickly for you.

I have to say though, if it had been me, I would have gone to a proper auto electrician because they are a trade/specialist in their own field. Mechanic for mechanical issues, body shop for body work, electrician for electrical work. I doubt very much that Lexus will have their own specialist auto electrician on staff; I can't imagine them having enough work to employ a guy for 37.5 hours/week.

Thank you. Yes, I see your point and that will be the next step if the garage can't sort it. By the way, this is an independent specialist and not Lexus, but your point certainly still stands.

I still get PTSD from the last car, so I hope it goes differently this time. That said, perhaps I'm being a little unfair comparing a Peugeot to a Lexus of the same era 😁

[ntl]

Update:

The gear selector issue is fixed - it was a seized ball joint on the selector unit. Once freed, it slots into position smoothly and every time.

The drain issue hasn't been so simple unfortunately. It was traced back to an ECU fuse that when pulled drops the drain down to a more acceptable 0.04 amps. That fuse has 30+ modules associated with it apparently! I could take it to an auto electrician but the problem is that there's water getting in somehow and so even if the bad module were located and cleaned up/replaced, this could easily happen again. This problem started after about three days of heavy rain. The passenger side footwell is damp under the carpet, and there aren't the usual signs of water running down pillars etc.

[Herbie]

2 hours ago, ntl said:

The passenger side footwell is damp under the carpet, and there aren't the usual signs of water running down pillars etc.

Glad you got the gear selector issue fixed.

Fingers crossed, going downhill with a tailwind behind you, the topic below from the American forum may just help you with the water ingress (particularly from Post No.16 onwards):

https://www.clublexus.com/forums/rx-2nd-gen-2004-2009/648923-sunroof-moonroof-leak.html

[ntl]

46 minutes ago, Herbie said:

Glad you got the gear selector issue fixed.

Fingers crossed, going downhill with a tailwind behind you, the topic below from the American forum may just help you with the water ingress (particularly from Post No.16 onwards):

https://www.clublexus.com/forums/rx-2nd-gen-2004-2009/648923-sunroof-moonroof-leak.html

Oh, that looks interesting - I'll have a good read through. Thanks!

[ntl]

I had forgotten about this thread, sorry guys! But here's the conclusion for anyone reading with a similar problem:

The drain was caused by an iPod connector in the glove compartment! Apparently it's not a factory fit, but an accessory that gets installed at the dealership when the car is first purchased. I didn't even know it was there. As soon as it was removed, the drain dropped down to normal levels 🤦🏻‍♂️

[ColinBarber]

On 6/2/2023 at 12:13 PM, ntl said:

Apparently it's not a factory fit, but an accessory that gets installed at the dealership when the car is first purchased.

Glad you found the issue 👍

 

The iPod connector was a dealer fit accessory that could be installed at any time - they weren't standard so most RXs won't have one. Not the first time I've heard of an aftermarket add-on being the cause extra drain -  seems they develop faults as they age which causes the extra drain. Probably due to not using automotive grade components that cannot handle long term temperatures and vibration that car electronics experience.