MK4 LS400 ECU swop and capacitor issue

[Malc1]

19 hours ago, Razor61 said:

The eBay key I’ll have a go at again, not hopeful though

can you send this back if it fails  ?

Can you name and shame the manufacturer / seller of this dumpster product maybe ?

Malc

[Razor61]

Small update to follow on from yesterday.
When the ECU is in ‘Auto Programming Mode’ for new keys after the immobiliser reset, as if a brand new ECU has been installed, the ECU wants 4 keys programmed before it will exit/end ‘Auto Programming Mode’, with the final 4th key assigned as a Valet key. I knew this, hence the reason I bought an eBay key so I then had 4 keys, which didn’t work in the end and only my existing 3 x keys could be programmed. If the 4th key isn’t programmed, the car/ECU stays in ‘Auto Programming Mode’ for days/weeks/months with the security light flashing when a programmed key is inserted until it eventually gives up. A bit annoying, even though this is a ‘temp’ ECU but the car still starts and runs so no big deal. However, while playing around with Techstream this morning connected to the car, to see if there was a reset/clear function for the immobiliser, I noticed a very nice utility to end the ‘key’’ Auto Programming Mode. So gave it go and no more flashing security light. Checked how many keys are programmed to the ECU and it’s 3 x master keys, which is correct for what I’ve done. Even with Techstream a master key is needed to clear keys etc, so Lexus were correct about this.

This post is a mixture of information, trial and error, failure and then success in the end installing a used ECU with the immobiliser chip ‘reset’ so ‘keys’ can be programmed to ECU and car will start and can be used.
Now I have a full/fulller understanding of what’s needed and how to do it, I’ll either create a new post or a ‘How to’ guide dealing with just the immobiliser chip ‘reset’ stuff.

[Razor61]

7 minutes ago, Malc1 said:

can you send this back if it fails  ?

Can you name and shame the manufacturer / seller of this dumpster product maybe ?

Malc

I’m not bothered about sending it back, it wasn’t an OEM Lexus/Toyota key and it was a bit of a punt on my part as to whether it would work or not. It’s probably ok and will work with other cars but not mine, maybe down to the frequency of the transmitter or something. Fortunately I didn’t get it cut to the ignition barrel cos there was no need, just removed the innerds and put in one of the other cut keys.

[Razor61]

On 5/13/2023 at 2:33 PM, Razor61 said:

When I get some plugs to power up the spare cluster on a bench, I’ll have a go at the mileage correction.

Not got the plugs but I have looked at a spare cluster I have to determine what IC/chip needs to be reprogrammed.
This is for a 97-2000 LS400, earlier models will probably be different.
The IC/Chip is IC8 on the main board, it is a surface mount IC, same size and shape as the immobiliser IC/chip in the ECU.
I tried reading the chip ‘in circuit’ without removing, same as the ECU immobiliser chip and can’t do it so needs to be removed. I am confident that once removed it can be read and reprogrammed for the correct mileage.
However, my opinion is that if anyone needs to replace the cluster and keep the mileage correct then either swop the main circuit board if it’s ok or swop over IC8.
IC8 is located under a heat sink for voltage regulator IC1 so the heat sink needs to be removed and is fixed with a bolt, spring washer and nut.

[Razor61]

ECU update……
Received the rebuilt ECU back from Bill in the USA, very professional service and shipped back to me without any hassle and packaged excellently.
Fitted it to the car after work today, connected the Battery and left the ignition on for a few mins before starting, as instructed. Put the key in and turned, car fired up immediately and I mean immediately with no cranking. Good sign that it was worth doing.
Tomorrow will be interesting going to work and I will be able to give more info on what difference/s it has made to the car. Main thing is it works and the caps have been replaced to prevent any issues in the future.
I now have a spare good ECU, proven in my car for the past 5-6 weeks, with a master key and an uncut blade. It is for sale now if anyone is interested in doing what I have done.
I’ll update this thread again tomorrow after work or maybe when I get to work, tempted to go for a drive now but it can wait until tomorrow.

[Razor61]

13 hours ago, Razor61 said:

Put the key in and turned, car fired up immediately and I mean immediately with no cranking.

Just thought, I forgot the car was still warm and it fires up straightaway anyway when warm so that's no different. A couple of cranks this morning when cold so that hasn't changed.
Was there any difference driving 10 miles to work? I believe there is a difference and feels even more responsive, it feels quicker and I don't have to press the accelerator pedal down as much. But it's early days and this may be all in my head...............the more I drive the car the more I'll be able to tell plus it will take time for the ECU to adjust correctly.

This is a definite though:
Swopped the original ECU for the 'spare' ECU - 100% sure the car performed significantly better. I can only assume the 'spare' ECU capacitors etc were more efficient and in better condition than in the original ECU in the car.

Time will tell if the rebuilt original ECU has improved things again, I think it has but as said above I need more time driving the car to make a judgment. Initial impressions are good though.
You never know, the car may be able to get near the quoted performance spec of 0-60mph in 6.3 seconds, which is pretty quick for a big car and pretty quick by any standard tbh. When everything has settled down I'll find out🙂

[Malc1]

8 minutes ago, Razor61 said:

performance spec of 0-60mph in 6.3 seconds,

 ............. for decades now I've been under the impression it was  6.9 seconds  ?

Well done whatever

Malc

[BigBoomer]

I've seen various figures quoted for the various LSes from 7.2 down to 6.2 secs.
I think the best description of it is adequate without being violent.  

[Tinonline]

2 hours ago, Malc1 said:

 ............. for decades now I've been under the impression it was  6.9 seconds  ?

Well done whatever

Malc

Later ones are in the low ‘6’ 😁🫣

[Malc1]

3 hours ago, Tinonline said:

Later ones are in the low ‘6’ 😁🫣

Buy newer, pay more and go slower 🥵

Malc 

[BigBoomer]

2 minutes ago, Malc1 said:

Buy newer, pay more and go slower 🥵

Malc 

Nope, they actually started off slower, especially the Mk1 & 2 due to less power (8.0 secs).
The Mk3 got faster (7.2), 1997 was 6.9, but the Mk4 was the fastest to 60 at 6.2 secs.
In the LS430 they were all 6.6 secs, LS600h was 6.2, the LS460 was 5.7, and the LS500h is 5.5.
So the Mk4 LS400 was the blip. Otherwise they got steadily faster to 60. Interestingly the LS430 is the same as the Mk4 LS400 over the 1/4 mile.

Not that it makes much difference to me. I used to do motorcycle drag racing in my youth and have ridden motorcycles since I was 14 so it's rare anyone beats me off the line.
I once humbled both an M5 and a Porsche 996 with my 202Bhp/1900Kg Honda Legend barge. Reflexes and front-wheel drive traction always beats too much power and too little grip.
They were so focussed on each other it never occurred to them that the old geezer in the barge was a threat 🤣
By the time their traction control had recovered I was long gone.

A friends tuned RX7 beat the Legend easily, but then twice the power and half the weight has that effect.
Even my GTR1000 (4.0s 0-60) struggled to beat that thing!

[Malc1]

TAKES ME longer than 6.9 secs to get outta bed these days .  0 - 60 ........ stairs would take me maybe 30 mins too 😇

I marvel at the turn of speed my dear old Mk3 Ls400 can achieve ....  sure beats hands down most cars I see on the roads these days .  in normalish driving conditions

Malc

[Razor61]

On 5/11/2023 at 12:55 PM, Tinonline said:

Hi

Forgive me for asking…what’s the cost implication of such a repair?

Simon

Carriage to send it the USA was £46, cost for the ECU rebuild was £400 + £48 carriage from the USA back to me.
Total was £494 in total for my ECU, price for a rebuild is dependent on if and how much remedial repair work needs to be done i.e pcb repairs due to leaking caps and corrosion.

[Razor61]

After a week or so driving to work and back I’m sure the rebuilt ECU has made a difference, not as much as the ‘spare’ ECU made but a definite improvement over that.
Lower end torque is better for sure, not easy to describe but you can ‘feel’ it when driving. Another thing is the cruise control is better, it doesn’t fluctuate as much and is more stable. Probably due to the lower end torque improvement. Gear changes seem better but I can’t swear to it. I can’t say anything about MPG yet until I go for a decent run, it’s about the same going to work and back though.
 

[Razor61]

On 7/5/2023 at 4:37 PM, Razor61 said:

can’t say anything about MPG yet until I go for a decent run, it’s about the same going to work and back though.

Went for a decent run, 70 miles round trip, mostly motorway, and I can now say something about the MPG.
70mph on the M55 motorway and the average was a very steady 36 mpg, which is pretty good. After this trip the mpg going to work and back has improved, around 26/27 mpg which is better than before and was a big surprise. To begin with, MPG to work and back wasn't much different and was down to 20/21 mpg. Not easy to quantify this sort of thing but I'm sure MPG is generally improved.
After installing the rebuilt ECU it has taken a while for things to settle down and the ECU to do it's learning thing. Idle speed was too high to start with but is now back to normal. I am guessing (educated guessing) that now the ECU has settled down and done it's learning, this has improved the MPG. I was told that MPG should improve significantly, I was sceptical to be honest but seems like it has.