Transmission Problem - Please Help

brucey72 · December 2, 2014

Just read through your thread. Fingers crossed you finally get to the bottom of this mystery!

Lexus-IS · December 2, 2014

Heard back from the dealer, apparently the neutral position switch is heavily coroded and so are quite a few other connectors which will need to be replaced as a loom repair instead of a loom replacement. The cost of the parts has been quoted in at £535 and they are quoting £500 for labour which they claim is approximately 4 to 5 hours labour. Seems very steep

johnatg · December 2, 2014

Hmm - that's all a bit worrying for the rest of us! Not surprised - diagnosis certainly fits the symptoms. It's a bit wally of them that they couldn't find it in the first place - this attitude of 'nothing wrong if there's no fault code' is typical of reliance on 'modern' technology instead of good old fashioned garage know-how.

Main dealer labour charge of £100 per hour is pretty average - cheap even if you were in London (which I guess you can't be). I expect most of the loom could be saved, but that might take hours and hours - and anyway, main dealers don't fix faulty (or even dirty) items - just rip it out, chuck it away and fit a new assembly. And (almost) no Lexus parts are cheap.

Not that I'm cynical of course......

Lexus-IS · December 2, 2014

Yeh I was considering getting the parts second hand but then might end up with the same problem again and will need someone to carry out the work. They claim the parts need to arrive from Belgium so will take few days. Apparently they've discounted it to the best price they can do and are not willing to go any further down. That's a total cost of £1,035 for a wiring and switch job. Yikes just sounds horrid. I would have thought these components being so expensive should be better protected from the elements.

Just wondering if these issues can have something to do with the gear changes not being smooth? And why is it that when the issue arises with the D and N sticking together and i let the car sit for a while and restart it, it clears out?

Also wondering if replacing these things could possibly be a DIY job to save £500?

johnatg · December 2, 2014

Anything is diy if you've got the skills, facilities and test equipment. I think the main problems here will be access - the electrical switches etc for the transmission are situated on the nearside (rh drive cars) of the casing. The neutral switch is mounted high up near the front of the transmission. I suspect that getting to it and the wiring will be one hell of a job and it will be impossible unless you can raise the car safely to more or less head height (ie a lift is going to be all but essential).

I think it's a good bet that fixing these issues will fix the gearchange problems you've experienced (but you might want to consider a bit of changing of the ATF as I mentioned before). Yes it's expensive - but I'm afraid that's the consequence of driving a particularly complicated car and despite usual near-perfect reliability, when something does go wrong it costs. On balance, I think that even I would go to a dealer for this. It might be false economy to compromise - but your decision.

The car probably has 50K miles, maybe much more, left in it - consider its actual value now and its value to you. Or consider what someone else did recently when confronted with a major expensive problem - ask them how much they'd allow in p/x for it unfixed against a new or stock s/h car? If you're in a position to cope with that!

ColinBarber · December 2, 2014

sounds like they are ordering a new loom and will just cut off the connectors and use on your old loom? I guess from a labour point of view that will be the cheapest way, but you pay for an expensive loom.

What is the history of the vehicle? Flood damaged, located near the sea?

Lexus-IS · December 2, 2014

@john, I am considering holding on to the car for at least another year or 2 or getting it to the 200k mileage and then let it go for whatever part exchange value i get. By then a pre-used IS300h should drop in price slightly.

sounds like they are ordering a new loom and will just cut off the connectors and use on your old loom? I guess from a labour point of view that will be the cheapest way, but you pay for an expensive loom.

What is the history of the vehicle? Flood damaged, located near the sea?

@ColinBarber, no flood damage or any kind of deep water issues. Have had the car for almost 8 years full Lexus service history up until about 140k miles. Had the solenoid work carried out at about 138k miles and since then things been going downhill. They claim it's a coincidence and that this isnt related, which i guess technically is true. The dealers did say that this method they using is repairing most of the loom by changing out the connectors rather than changing the loom which they claim would take the bill to couple of thousand. My worry would be that I hope the crimp the new connectors correctly and use the correct rubber seals on them. They say it will come with a 12 months parts and labour warranty

ColinBarber · December 2, 2014

I'd like to think they would solder, heat shrink, and waterproof the joints rather than using crimps - and ideally make the cut as it enters the cabin (if it does) rather than on the exterior.

Seems odd that there is corrosion on these connectors, normally Toyota connection blocks are good at stopping that happening, and even if the exterior of the connect did get corroded the touching surfaces would normally remain clean. I wonder if these connections were disconnected when the other work was carried out?

Lexus-IS · December 2, 2014

@ColinBarber im not sure if these connectors were disconnected when the solonoid work was carried out. I guess it's worth questioning them about it. It seems odd that they claim not only has the neutral position switch completely gone bad but a good few connectors too. Is that a coincidence? Other than the usual heavy rain we've had, haven't had any floods this year.

I would think that a switch like that which plays a huge importance to the transmission would somehow be protected from the elements. My collegues 3 series which is 1 and half years older has 210k miles on the clock and on all original transmission parts. His had it since new and no work on transmission. Mines only at 160 which is low compared to his 3 series

ColinBarber · December 3, 2014

I've been on this site for over 11 years, and I try to read every post across all forums, and in that time I've never heard of this across any Lexus model.

Lexus-IS · December 3, 2014

I find it odd that not only has the Neutral Position Switch heavily coroded, but also the connectors. It's a hell of a coincidence. Apparently the AirCon pipes run near this location and the condensation from it may be the culprit. If so, then isnt that a serious design flaw?

johnatg · December 3, 2014

I don't think it's very likely that the aircon pipes have anything to do with it - they don't get any significant condensation. There is a drain from the evaporator, but that shouldn't discharge at all onto the transmission unless it's been damaged or misrouted.

I think I might spray a dose of waxoyl over the electrical units on the side of my transmission when I get the chance - it does a good job of protection against damp and in particular the salt in road spray.

Do you live by the sea or somewhere that uses huge amounts of salt over long periods of the winter?

Lexus-IS · December 3, 2014

@john, no nowhere near the sea and just the usual winter road salting which to be honest hasnt even started this year.

Lexus-IS · December 6, 2014

Got the car back. Haven't driven enough to be able to tell difference in terms of gear changes. Will see how it goes when driving to work during the week. The invoice says Found Neutral Isolation switch A full of water and loom connectors corroded. Replaced isolation switch and carried out repairs to loom connectors. The isolation switch it's referring to I am assuming is the same as the Neutral Position Switch as I googled the part number: 8454071010 from the invoice and came across these pictures:

I have no idea how water got in there because i've never driven over lots of water. One theory they have but cannot be sure about is that it has collected over the years from the condensation pipe of the A/C.

I'm wondering, why is it that the corroded/damaged Isolation Switch/Neutral Position switch did that N and D thing randomly and then the last time when it did it, I turned the car off and on and it was still doing it but then after leaving it overnight and when starting it in the morning to drive to the dealers, the N and D confusion wasnt happening, but by this time a code had registered already. I showed them a video and apparently they were able to replicate the D and N coming on together again when they had it in.

johnatg · December 6, 2014

I guess it's just that corrosion and water penetration into any electrical system causes unpredictable, intermittent and random errors. Electric current finds its own path - very slight changes in the degree of corrosion or amount of water can cause changes. If the damage was really as extensive as apparently reported it's surprising that it kept working at all. I suppose the whole thing is a bit like thumping the side of a TV to get it working (some of you may remember we used to have to do that every night!) or shaking a torch.

And there's the standard cure for anything electronic - switch it off and on again!

Lexus-IS · December 14, 2014

An Update. I've driven the car for a full week to work and back daily since the repair. The problem hasn't returned. Although the non-smooth gear changes haven't improved, i've observed a few things and not sure if the ECM or ECU is gradually re-adjusting because it seems to be getting a little better. The work involved changing the Neutral Position Switch and about a total of 9 or 10 connectors.

First thing I noticed is that before having this work carried out, For a few years now, when I used to start my car on a cold start the revs used to start high at about 17-1800 rpm and then within a matter of 4 or 5 seconds it used to drop to about 900 and then shoot up to 1700 for a split second and then stabilize at about 1400ish rpm depending on how cold it is. But towards the end of the week I noticed that this problem went down significantly. On one occasion both in the morning to go to work and evening to come back, this did not happen. It used to always happen before. But the next day it was much colder and it happened but nothing like before and the rpm didnt shoot up for the split second like it used to but instead just surged by a few hundred rpm. I never knew what was causing this issue, I changed MAF sensor back then and even cleaned throttle body but made no difference. But this work seems to have helped this alot.

Second thing i've noticed is that the car although is not smooth through the gears specially the lower gears, it's much more responsive. Not sure how the work has helped this.

ColinBarber · December 14, 2014

The transmissions are somewhat self-learning so you may find it gets a little smoother / less responsive depending on your driving style. Give it another week or two.

Lexus-IS · January 5, 2015

OK so few weeks on a one issue really mainly observed. The unsmooth upshifts have become better. But the car seems to have developed a completely new jerk which feels even worse and happens mainly on 3rd and 4th gear, if i accelerate and then let my foot off the throttle at times i get a really noticeable jerky gear change like feeling but it hasnt changed gear. If i gently pickup speed and it's on 3rd or 4th and i'm accelerating slowly and let off the throttle while moving slowly then i get a back and forth jerk. This only happens once warmed up.

Rizmo · March 30, 2018

I have Lexus IS 250 I got problem with automatic transmission when i drive it’s changing to 1-3 gear then drive as normal the gear won’t change 4/5/6 any body got this issues pls ? When I diagnosed it’s said

solenoid valve D remain open

valve C remain open

Any one has this issues? I am thinking still worth to repair?

ColinBarber · March 30, 2018

Have you checked the fluid for condition and at the correct level? If that is ok then the solenoids will need testing/replacing. If that is all the problem is then it is relatively minor and so would be worth repairing.