dandare

Hello and greetings to all.

I'm a new member, as you can see. I have a March 1997 LS 400 (is that 2nd gen?).

The other day, after not using her for a couple of months, I realised I have a flat battery.
I jump started the car with some cables and it ran fine. I left it ticking over for 20 minutes, and then went to turn the lights on. At which point the motor stopped. There was still absolutely no charge in the battery, so I jump-started her again. This time she started, but would not idle.
Everything runs fine except she refuses to idle.
I charged the battery and she starts, but still has the same idle problem.

Have I inadvertently reset something in the ECU?
Any ideas on how to solve this?

Apart from this "little" problem, I am in awe of the quality of the vehicle. So smooth and comfortable. I bought it cheaply a couple of years ago, and it runs beautifully.
There are some other slight problems to be attended to (wishbone bushes and rusty rear subframe, among other things), but I think she is a keeper.

Regards and thanks for any help in advance.

Daniel

AandSC

Have your battery tested at an auto parts store. You would be surprised at how many odd symptoms a bad battery will cause.

Yamae

Discharging a battery very slowly causes a slow voltage drop which sometimes causes strange problems in the C-MOS cell in the ECU. Some electrons still remain and the system does not work properly.

The problem can be mostly fixed doing these below step by step.
1, Connect a well charged battery.
2, Turn the ignition key to the on/run position until the VSC/traction light goes off. It takes about 20 seconds. Do not start the engine while this.
3, Turn off the ignition key and remove it.
4, Disconnect the battery.
5, Wait for whole 1 day or more. (24 hours or more)
6, Connect the battery and turn the key to on/run position and wait until the VSC/traction light goes off.
7, Start the engine.

If these are not effective, check the ripple level as is explained in the FAQ.

djamps

Check for power steering leaking on your alternator.

dicer

Yamae, is that true with the Gen 1 also?

dandare

Thanks AandSC, but I did manage to charge the battery and it showed 12.96 Volts on a multimeter, and without connecting it to the car, it still showed 12.9 Volts a day later. I don't know much about batteries, so you could be correct, but superficially it looks ok.

I'll check it again today.

Regards
Daniel

dandare

Thanks for the answer Yamae,

I'll try your way first.

I didn't even know I had traction control. It certainly doesn't seem to work. I've never seen a symbol for it on the dashboard.

I had a search for ripple level in the forum, but only found a mention of it once, but without an explanation. I'm new here, so perhaps not so good at finding things out.

I did find something about capacitors failing in the ECUs, so maybe that is something to do with it?
The car always ran very smoothly (and still does), is fast and economical (for a V8), so I didn't think it would be the ECU, but of course the ECU does control the idle.

Regards
Daniel

dandare

Thanks djamps,

No leaks!

Daniel

dandare

Update:
I did as Yamae said, but there was no VSC light, so I waited 20-30 seconds and started my car. Same problem - she wouldn't idle. I turned her off, and then on again without starting her, and sat there in despair. I noticed some whirring and clicking coming from the dashboard (I thought they were the ventilation motors moving around?), and then after a while the noises stopped. I then started the car, and she idled perfectly. Yippee!

I may get a new battery anyway (although they are 150 Euros in Germany), when funds allow.

Thanks to all for the suggestions, especially Yamae.

Now for my other problems. Should I start a new thread?
Was VSC an option, because I definitely don't have a light for it on the instrument binnacle?

Daniel

Yamae

Congratulations, Daniel. I'm glad that you succeeded to revive your 97 LS400 resetting the ECU completely. My method is based on the theory and my experience to revive half dead computer systems. It is not written in the service manual at all, but I know some about electronics controlled systems and I always use my method when asked by local shop owners to help.

Regarding the VSC, here in Japan, all the UCF20/21 have it but I don't know European models have it or not. Anyway, it is important to wait some before starting the engine when the ECU needs to relearn. The purpose to wait 1 whole day is to fully discharge the unwanted electrons in the cell.

I don't know the Gen1 well as much as you know, dicer but, my method should be effective to those too. Why don't you try? But I don't want you to damage your ECU.

The slow voltage ramp up/down is not happy for many ECUs as well as general computer controlled systems. It is not easy for the circuit which detects the voltage ramp to work properly when the voltage ramp is extremely slow and fails the initial reset or to do the final closing processing and results the mess in the system. This sometimes needs a few days to discharge the electrons remaining in the C-MOS cell.