IS250 Transmission errors

Lswood · September 4, 2020

Hi All
I'm new to Lexus ownership and new to this forum. I know very little about cars except that Lexus is a solid brand. I bought an automatic 2005 IS250 SE-L about a month ago. It's got just over 135,000 miles and there was no service history (I know!!) but I desperately needed a car. A friend who loves Lexus saw it for sale in his neighbourhood, looked it over and got it for me for a good price. The car is in good physical condition (beautiful leather seats, satnav, Mark Levinson system, rear camera etc).

However a week after buying it, the check VSC light has come on and gone off periodically. A mechanic looked it over and said there was absolutely nothing wrong with it. Light came back so after checking this forum, I changed the gas cap. After the VSC light reappeared I took it to a large garage. A couple of very worrying errors came up
C1201 - ECU Faulty operation
P2714 - Pressure regulator solenoid valve, component remains open
P2757 -Torque converter, coupling pressure, component remains open

The garage is saying the first recourse would be a gear oil change (£300-£400) but it could be a more serious transmission issue that costs thousands up to a complete replacement. The garage is however not experienced with automatic transmissions so he's just guessing. The car is still driving beautifully and I really want to keep it as I've already fallen in love with it so I'm willing to invest a little but wondering if I should.

Has anyone had experience of either one of these errors and how much money am I potentially looking at in a worst case scenario of replacing the transmission? Are there any good independent garages in south east London that have expertise in Lexus or auto transmissions?

ColinBarber · September 4, 2020

Worth getting your 12v Battery tested. If it is on its way out you can get all sorts of spurious error codes.

Alfalfa · September 4, 2020

Get new oil, flush out.

Lswood · September 6, 2020

Thanks for the advice

m4rkw · September 6, 2020

On 9/4/2020 at 6:56 PM, Alfalfa said:

Get new oil, flush out.

Don't flush it. That won't help and can even cause damage. The correct way to service the transmission is to drop the pan, drain the fluid out, replace the filter assembly and refill with the correct fluid. If you have no history and the fluid looks black then you definitely want to do this at some point if you plan on keeping the car, ideally as soon as possible once you've made sure that whatever the current issues are aren't terminal.

If it drives ok it may just be electrical glitches as Colin suggested. I'd start with the Battery, if that checks out, take it to a Lexus specialist and ask them to diagnose it. Or perhaps an auto electrician since the issues point more towards electrical if the transmission is shifting ok.

nicnac · September 7, 2020

You do need to check for correct fluid level in the transmission . IT IS CRITICAL that it is correct at the correct temperature.If it is very brown in colour you need to cycle fluid through it a few times with the drain /fill recheck level procedure . There is a great youtube video that can help you here .

If you do this and reset the system useing Techstream Software and go from there !

ONLY TOYOTA WS TYPE FLUID

Alfalfa · September 7, 2020

17 hours ago, m4rkw said:

Don't flush it. That won't help and can even cause damage. The correct way to service the transmission is to drop the pan, drain the fluid out, replace the filter assembly and refill with the correct fluid. If you have no history and the fluid looks black then you definitely want to do this at some point if you plan on keeping the car, ideally as soon as possible once you've made sure that whatever the current issues are aren't terminal.

If it drives ok it may just be electrical glitches as Colin suggested. I'd start with the battery, if that checks out, take it to a Lexus specialist and ask them to diagnose it. Or perhaps an auto electrician since the issues point more towards electrical if the transmission is shifting ok.

Drop the pan and change 1 litre? i flushed mine, got a better gearbox, but i cant promise that it vil cure his gearbox, but my car gear a lot faster now. My car was flushed vith the Toyota WS Fluid only, not the cleaning fluid normaly used first in the Flushing. Have 5000km on the meter after Flushing, no isues.

m4rkw · September 7, 2020

Experienced technicians advise against flushing unless as a last resort. If you only get 1L out by draining from the pan then I'd just repeat the process a few times.

m4rkw · September 7, 2020

In any case it's not entirely clear that OP's problem is actually an internal gearbox issue, it sounds more likely to be electrical.

nicnac · September 7, 2020

2 hours ago, m4rkw said:

Experienced technicians advise against flushing unless as a last resort. If you only get 1L out by draining from the pan then I'd just repeat the process a few times.

I am an engineer !! and I was also a IS250 owner that had gearbox issues back in 2009 . Read my past posts from that era . I despair at this attitude which at best is ill informed . I now own a Sc430 which has a nearly identical 6 speedtransmission and can supply the toyota pdf for transmission oil cycling etc if needed by anyone who doesnt put there head in the sand and wait for christmass !!!!!!!

Alfalfa · September 7, 2020

2 hours ago, m4rkw said:

In any case it's not entirely clear that OP's problem is actually an internal gearbox issue, it sounds more likely to be electrical.

True, but my advise about Flushing is related to the 130000Miles on the meter, and if you are lucky the problem dissapear, and yes if you drain the pan 15 times you get the old oil out, but a expensive solution.

nicnac · September 7, 2020

He need to eliminate that there is a fluid issue before going any further . Without techstream and a logical approach he is useing the scatter gun technique of diagnosis !!!!

m4rkw · September 7, 2020

Information here on transmission flushes from an experienced tech working on Toyota/Lexus for 30+ years: http://www.agcoauto.com/content/news/p2_articleid/238

Everyone is entitled to their own opinion but I’ve seen enough credible people say don’t do it.

nicnac · September 7, 2020

8 minutes ago, m4rkw said:

Information here on transmission flushes from an experienced tech working on Toyota/Lexus for 30+ years: http://www.agcoauto.com/content/news/p2_articleid/238

Everyone is entitled to their own opinion but I’ve seen enough credible people say don’t do it.

Mark ,

This is NOT a FLUSH in the traditional meaning .

It is a procedure to cycle the oil , replacing appox 2 litres at a time to cycle the oil through the system .

It was Lexus Belfast that origionally caused my issue ., and there so called technicians.

The procedure is a proper procedure provided by LEXUS , the manufacturer.

I would add , I am 68 .... Was a qualified aircraft engineer . Then changed to Electronics in the 80,s and during all my years did varios projects with cars , engine and transmission rebuilds , so take your choice what advice to follow

Tr Fill.pdf

m4rkw · September 7, 2020

Sounds like we’re talking past eachother, the document you linked seems to be describing a normal transmission service rather than a flush. If that’s what you’re advocating then it seems to be very a different procedure from what is commonly referred to as a “flush”, it seems to describe re-filling the unit to the correct level after a service. That’s very different from the “flushes” described elsewhere. Perhaps this is a loaded term with more than one interpretation and we should avoid using it without clarification?

nicnac · September 7, 2020

Incorrect final level checking on this transmission can cause various symptoms from notchy changes to gears not even selecting .There are multiple solenoids ( electrical) hydraulic in the transmission which can malfunction if the fluid level is not within spec.

So it is imperative that the procedure is followed precisely .

This is an elimination process in the case of the original snag !

A960E.pdf

m4rkw · September 7, 2020

1 minute ago, nicnac said:

Incorrect final level checking on this transmission can cause various symptoms from notchy changes to gears not even selecting .There are multiple solenoids ( electrical) hydraulic in the transmission which can malfunction if the fluid level is not within spec.

So it is imperative that the procedure is followed precisely .

This is an elimination process in the case of the original snag !

Appreciated, but in the initial post the OP said that the car drives and shifts fine, other than the error codes he apparently had no symptom of a transmission issue. That's why my first inkling was electrical rather than a transmission problem. But it can't hurt to check such things for sure.

nicnac · September 7, 2020

4 minutes ago, m4rkw said:

Sounds like we’re talking past eachother, the document you linked seems to be describing a normal transmission service rather than a flush. If that’s what you’re advocating then it seems to be very a different procedure from what is commonly referred to as a “flush”, it seems to describe re-filling the unit to the correct level after a service. That’s very different from the “flushes” described elsewhere. Perhaps this is a loaded term with more than one interpretation and we should avoid using it without clarification?

If you notice I never used Flush.......... only Cycle . Please look at the youtube video . and it all becomes clear . What I am advocating is the fluid cycling to replace as much as possible ( i do it 4 times ) then the final level check .iaw the procedure . Then if he still has fault codes ... you go from there !

nicnac · September 7, 2020

3 minutes ago, m4rkw said:

Appreciated, but in the initial post the OP said that the car drives and shifts fine, other than the error codes he apparently had no symptom of a transmission issue. That's why my first inkling was electrical rather than a transmission problem. But it can't hurt to check such things for sure.

Yes , but the malfunction and subsequent code flagging can be the product of incorrect level fluid or its condition . Those codes in the main relate to the valve body of solenoids in the transmission . .

m4rkw · September 7, 2020

1 minute ago, nicnac said:

Yes , but the malfunction and subsequent code flagging can be the product of incorrect level fluid or its condition . Those codes in the main relate to the valve body of solenoids in the transmission . .

Fair enough, you probably know a lot more about this than I do. Wouldn't low fluid cause the unit to slip or give other noticeable signs though?

nicnac · September 7, 2020

Its a complicated piece of kit and full of wires to all the solenoid bodies that are sitting just above the the oil pan level .

Not necessarily to the slipping the torque converter is supplied with oil from the sump and as long as there is enough not to cavitate it wont slip . At 130K the WS fluid needs replaceing by the cycle method . It can function longer and does in many transmissions of the A760/A960 E types , but at 50 K its pretty dirty ...................I know been there a few times !

nicnac · September 7, 2020

First thing I would do is clear all codes on Techstream . Then reset the Engine and Transmission to defaults . take her for a run and then recheck . It is possible that they will disappear. If they reappear then you can use the utils on techstream to check various operations of the transmission . If this does not make the codes go away , then I would look at the transmission oil as possible cause .

I wonder if the Lexus Techs did any of this ?????????

nicnac · September 7, 2020

Just googled this for info

P2714 is a problem in the SLT solenoid. I had the same problem. Eventually i opened the pan, replaced the SLT solenoid+atf filter+atf fluid+pan gasket.
Now the car works fine about 5,000 km