P1780 Code......is It Essential?

[janet]

Hi all,

I have a P1780 (Park/Neutral position switch malfunction) with the engine warning light on all the time.....everything works fine, no probs at all......cancelled once but now back on again......what's broke?...and if it ain't broke do I need to fix it ???? !!!

Any code experts still out there?

[fjcfarrar]

The fault may allow you to start the engine in gear & both that and the warning light might mean MOT failure.

It is probably a problem with the switch worked by the linkage to the gear lever to detect it is in neutral and/or its connector. You can find where it is by exploring the workshop Manual here:

http://bahamutcars.free.fr/workshop/IS_98-05/menu_tree.html

Once you have found it, you can check its function using a borrowed multimeter for continuity - unless it is obvious that the linkage is not mechanically operating it or it is misaligned etc. If faulty, you could obtain & fit a new switch - which won't be difficult. The workshop manual has links to how to check things and handy hints on replacing them when it is not obvious.

OR - if you don't fancy this which could get a bit greasy; you could get someone with reasonable common sense and ordinary tools to do it for you.

[janet]

Thanks fjc, I will get that sorted. Nice to know you are still dropping in to help out us cack-handed mortals!!

[janet]

Ha! The idea was to have a look today, but at 4am this morning, the horns started making a clicking sound, after it got me up and on the drive....no central locking... funny beeping noises from inside the rear nearside wing (alarm location?)......then it went quiet at about 5.30. Well after additional beauty sleep this morning I have been out and the Battery is flat. I am working on the water ingress theory after yesterday's deluge, but again the drivers footwell/fuses area is totally dry. Unless you brains can think of anything else, I will charge the Battery, get the sunroof open and check the drains as best i can.....

[fjcfarrar]

If this latest is NOT due to water-ingress affecting the ECU/Management System, it could be connected with the original neutral-detection switch problem. The switch-fault could be misleading the management system by not receiving the signal that the car is in neutral or just as likely thinking it is permanently in neutral - anyway sending unexpected and conflicting signals to the Management System, and then maybe not not completing the switch-off sequence because expecting you to restart the engine etc., and ending up running stuff in the background, thus flattening the Battery.

When the Battery gets close to flat, all sorts of strange things do happen with the anti-theft/alarm system which would account for the odd clicks and sounds.

The first step is to disconnect and fully charge the Battery. The disconnection will mainly reset the management system, and you can then see if too much current is being drawn with ignition off. Too much should definitely be a lot less than with the ignition on. I'm not sure what the standby current should be with the ignition off; but am guessing below about 50 mA with interior lights, exterior lights, fans and Radio all off.

You also need to be satisfied that the auto-lighting facility works reliably. The door-switches can cause this to behave erratically, not ALWAYS switching the lights permanently off when you leave the car. So until you have sorted the immediate problems, just leave the lights in manual mode.

None of your problems are likely to be due to failure of expensive parts and particularly not the ECU/Management electronic modules which very rarely fail - but are often incorrectly blamed. The real causes are usually very tedious to locate and involve peripheries like dirty or corroded contacts in fuse-panels, connectors and switches plus the rods, levers etc. that actuate them.

I would be inclined to start by looking for the original problem, because likely to be the root cause of other symptoms. Then if necessary, checking to make sure that water has not got into connectors and associated fuses to the ECU/Management System. All if you have no garage, in the pi**ing rain!

But I could well be wrong, and others will surely come up with better theories.

[ColinBarber]

possibly water ingress, poor earth connections or a collapsed Battery.

[janet]

Thanks ! Yes, I have had experience of the alarm systems 'character' before in the dead of night!, anyhow....battery on charge....if you could indulge me I have had a good look and feel around the drivers footwell/fuses area and as far back as my pinkies will go...bone dry, when charged i will open up the sunroof and have a poke around to hopefully clear the drainage tubes......is there any way you can test if the sunroof drains are working, without turning the car into the world's largest mobile fishtank?!... and where else might one have a peek/feel for the dreaded water?

[fjcfarrar]

Thanks ! Yes, I have had experience of the alarm systems 'character' before in the dead of night!, anyhow....battery on charge....if you could indulge me I have had a good look and feel around the drivers footwell/fuses area and as far back as my pinkies will go...bone dry, when charged i will open up the sunroof and have a poke around to hopefully clear the drainage tubes......is there any way you can test if the sunroof drains are working, without turning the car into the world's largest mobile fishtank?!... and where else might one have a peek/feel for the dreaded water?

If in this weather when you open the sunroof and the channels are dry - the drains are not blocked. Prove the point by squirting a little water into them from a discarded washing up liquid bottle and watch it disappear.

There are a few electrical bits and pieces in the boot eg. the bulb-failure detect module, so make sure that is dry too.

While you are at it, open each door in turn & make sure that the interior lights turn off EVERY SINGLE TIME when you press the door switches (in small rubber boots that are pressed when the door closes) & turn on again EVERY SINGLE TIME when you let go. If these are in the slightest bit erratic, the system can assume the doors are not shut or were never opened for you to leave the car & will foul up the operation of the Alarm System, auto-headlights and a few other functions of the management system/ECU to produce some really peculiar symptoms. If faulty, and these switches do fail fairly often as they get older and the contacts oxidise; they are easy to change with just a cross-head screwdriver - but the wires to them are very short; so tie a piece of string etc. to them before you pull the connectors off the switch to prevent the wires from disappearing down the switch-hole (they are difficult to retrieve).

Good luck! The IS300 is a fine car and worth going to a bit of trouble yourself before thinking about chancing huge expense with a Lexus garage - and to be honest, they will have difficulty with electrical problems unless they are very obvious.

[janet]

A brilliant reply, full of useful info...... can't ask for more !!!

[KentIS300]

My alarm desides to go on random occasions and loves it around 12:00 midnight or around 6:00 in the morning ... it is like it has an alarm clock in it lol

However after observation I have noiticed I have a little leake on my sunroof (when I pull the visor back) and after a strong rainfall I have a couple of drops fall on top of my head. If I keep the sunroof visor closed is perfectly fine.

Now the fun starts that night when condensation takes place the alarm goes off ... and the same in the morning time.

The condensation of the leak in the middle of the ceiling is setting it off. My problem has nothing to do with the windscreen some others are facing. One of these days I will clean the drains for the sunroon and I will try to revive condition the sunroof rubber somehow. As the water is only like 15ml .... MAX

This is a scenario you might want to concider as well if you experience random set offs.

Also I have read somewhere else that the bonnet alarm switch can malfunction setting off the alarm as well.

Also a low or poor health Battery will set off alarms with this kind of sound as you described... they think someone is trying to disable them and the thing is your cannot disarm the bl@@dy thing ... lol as the Battery is low and becomes unresponsive. Happened with my CL when the radio was draining the Battery after a 4-5 day of non use.

[janet]

Hi KentIS300,

Mine is now checked and still as dry as a British summer!, all drains OK.

My alarm problem, a couple of years ago... was mainly it setting off at stupid times 2am etc, in real hot summer weather! After much angst and even checking out a new alarm system, the nice people at Derby Lexus disconnected the roof sensor for me FOC (!!!) and since then no problems with it.

My little current (Ha ha!) problem may be sorted week after next when I have the auto lever switch renewed, and other bits attended to. Over 5 years hardly anything has gone wrong, just like the previous IS200, so a little TLC is well worthwhile.