PhilipMidd

My alarm in my 89 LS400 is not working and the Keyless lock/unlock is also not working. (who knows, probably all related). I'm about to try and put a new alarm in it, just a cheap ebay job that will do Keyless entry, Alarm, immobilize (simple open or close circuit). It also has a rollup windows function, but not too worried about that atm. That module is still on the way.
What I need is the wiring diagram or what coloured wires to splice where. Am I best off splicing into the Central locking computer in the boot, or just wire it in under the dash (if I can find room).

My car is actually a 89 JDM Celsior, but the wiring for this will almost certainly be the same as the 90-92 and probably up to 94 Lexus LS400

oldskewel

iTrader: (1)

Here's a clue, that might help ...

I've got a '91 (US) LS400, completely stock. Several years ago I realized the alarm was never helping anything, and was sometimes going off when it should not, so I disabled it.

There is a thread in here somewhere, with pics and everything describing exactly how to ground a certain wire to disable the factory alarm. From memory, it is a green wire near the fuse box to the left of the driver's (LHD) feet, that needs to be grounded. But a lot more clarity than that is needed, so search for the right thread on here that nails down specifics.

Anyway, after finally getting the right info with no guesses, I grounded the wire, and it successfully completely disabled my alarm.

HOWEVER, as I finally noticed a year or two after that, grounding that wire disabled the ability to unlock all 4 doors from the driver's door lock. I had not realized the two things were related, but after troubleshooting and testing, confirmed that's exactly what's going on. Un-grounding the green wire re-enables the alarm and also re-enables the 4-door unlocking from the driver's door key lock (turning once to unlock the driver's door, turning a second time to unlock all 4).

So caring more about the nuisance alarm, I re-grounded the green wire, killing the alarm, but also disabling this nice feature. BTW, 4-door unlocking still works when using the passenger door key lock (all 4 unlocked on the first turn).

Given all that, my guess would be that maybe some previous owner disabled this, causing both of your problems. Or at least that the two are related and if you fix one, you'll fix both.

PhilipMidd

Thanks mate. I'll do another series of searches to see what I can find.
I thought the 2 might be related as the alarm / key security / window winder all appears to be controlled from that one computer in the boot. Maybe not the window winders, not sure about them.
I'll do the research and then do some more exploration on the weekend.

Thanks again.
Philip.

dicer

My idea to disable the alarm is to unplug the hood alarm switch the alarm will never try to set then.

spuds

Interesting thought.Look forward to the follow up Dicer.I love ideas that are workarounds of the computers.

JonnyO78

Wanted to throw on here that EZKeys is working on replacement alarm options on my thread HERE. They're looking for schematics of the existing system to see if they have a suitable unit.

PhilipMidd

Yes.. I saw that post made about a month or 2 ago. Seems like a simple and elegant solution. Thanks.
I was planning to use that switch for the new alarm if I can find it, and if it exists on my car....I figure its gotta exist. I just haven't seen it yet.

dicer

The trunk switch could also be disconnected instead.
I leave my hood unlatched if I don't want the alarm to set.

timmy0tool

iTrader: (7)

wow, never knew there was a hood switch for the alarm the entire time of my ownership of the LS400!
where is the trigger, perhaps in the latch itself?

anywho back to the OP, have you checked all the fuses? I would try to see if the existing system actually works first before trying to bypass it with an aftermarket unit.
you will need the unlock/lock feature functional for the aftermarket alarm to perform keyless entry anyway.

also I'm not sure how to immobilze the LS400.
to my limited knowledge, to immobilize a vehicle the aftermarket alarm would stop the starter from engaging.
this would be in the ignition switch somewhere under the dash.

PhilipMidd

Yeah, I had a look today and could not find one. Will check the latch tomorrow. PITA to check that area.
Yes, first thing I did when I first got the car. checked all fuses and relays with a relay checker - all working OK.
I could just dodge around all that providing I can identify the wires needed to lock / unlock the doors.
I was thinking of putting the new alarm in the boot next to the central locking system as that probably has all the wires I need to plum into (and its a lot easier that trying to get under the dash - and to be honest, that the reason why the new alarm has not been installed yet).
I was thinking of simply grounding the coils. Its not exactly elegant, but it is effective and providing you dont do it at the coils, it can be really hard for someone to find. I was thinking of finding the right wire at or close to the ECU. That thing is a real pain to get to so figure someone is likely to give up before then (or disconnect the coils from the wiring loom and power them separately - but all takes time, time hopefully some car thief is unwilling to spend on stealing an essentially worthless pile of parts he couldn't move very quickly and I gotta face it, its not the kind of car a joyrider is looking to steal).