99 LX470 Auto Door Locks, KeyFob, and Electrical Issues

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Joined
Nov 17, 2021
Threads
3
Messages
15
Location
Santa Barbara, CA, USA
Hey guys, I got a 99 LX470 4 months ago with 241k miles on it. Since I bought it, the Key Fob does not work, the automatic door locks are defective, and electrical power is not delivered some systems when the car is off, such as the dome lights. More detail below:

For the Key Fob, the battery for both the main and spare key have been replaced, and the red light blinks when the buttons are pressed with no effect on unlocking/locking/alarming the car. I attempted reprogramming both Key Fobs with no luck, since it seems that no electrical power is delivered when the key is inserted in the ignition on the "LOCK" position.

This is indicated by the door open indicatior not chiming when the door is open, the dome lights remain off when the doors are open, and the radio's clock resets everytime the car is started. However, electrical power is still delivered to some components like the car horn and hazard lights without the key.

For the automatic door locks, they do not work without the key turned to "ACC" or "ON". The unlock function works flawlessly, however there is a frequent problem with locking the doors. When pressed for the first time, all doors lock. But any other time after the lock button is pressed once, the door locks switch to lock then a half second later, unlock. When repeating the attempt to lock the doors, the door locks lock with weaker and weaker force to the point of not locking anymore despite it "clicking". Additionally, the rear tailgate does not unlock with the key, only with the auto door locks. Not sure if that's an electrical issue or mechanical.

I am completely lost with this. I checked all the fuses and am fairly certain they are still good. I tried to reprogram but cannot since no power is delivered to the car when off as seen by the lack of dome lights and open door indicator chime with the key in "LOCK", yet power is still in the system as the horn and hazards work with the car off, possibly indicating a faulty fuse or relay. The battery seems good, and had no problems starting the car. Keyfob battery is brand new as well. OBD2 scantools doesn't mention anything either. Could be a faulty ECU but no other symptoms show for that.

Only thing I can think of is a busted relay or fuse that stops the alarm system and keyfob from working at all times, and the lack of electrical power that keeps the door locks and dome lights from working when powered off.

I'd like to hear what everyone thinks before I bite the bullet and take it to a shop or worse, a local lexus dealer. Any advice would be greatly appreciated!
 
Sounds like a bad relay, connector or door switch? Is the remote locking and alarm system stock? I had similar symptoms in my 99 LC when I bought it and it had an aftermarket security system fitted which had been wired in very poorly. One of the fuses in the left kick panel was blown (I think it was either the 10A IGN or 15A gauge) and the security system was wired over it. Truck still started and ran but no remote nor central locks anymore. After removing that mess and repairing all wires back to factory state everything worked again. While teaching the system new remote keyfobs I found out the front left door switch did not work very reliable, needed a couple attempts to get through the sequence. Still on my list to be cleaned or replaced.
 
Hey guys, I got a 99 LX470 4 months ago with 241k miles on it. Since I bought it, the Key Fob does not work, the automatic door locks are defective, and electrical power is not delivered some systems when the car is off, such as the dome lights. More detail below:

For the Key Fob, the battery for both the main and spare key have been replaced, and the red light blinks when the buttons are pressed with no effect on unlocking/locking/alarming the car. I attempted reprogramming both Key Fobs with no luck, since it seems that no electrical power is delivered when the key is inserted in the ignition on the "LOCK" position.

This is indicated by the door open indicatior not chiming when the door is open, the dome lights remain off when the doors are open, and the radio's clock resets everytime the car is started. However, electrical power is still delivered to some components like the car horn and hazard lights without the key.

For the automatic door locks, they do not work without the key turned to "ACC" or "ON". The unlock function works flawlessly, however there is a frequent problem with locking the doors. When pressed for the first time, all doors lock. But any other time after the lock button is pressed once, the door locks switch to lock then a half second later, unlock. When repeating the attempt to lock the doors, the door locks lock with weaker and weaker force to the point of not locking anymore despite it "clicking". Additionally, the rear tailgate does not unlock with the key, only with the auto door locks. Not sure if that's an electrical issue or mechanical.

I am completely lost with this. I checked all the fuses and am fairly certain they are still good. I tried to reprogram but cannot since no power is delivered to the car when off as seen by the lack of dome lights and open door indicator chime with the key in "LOCK", yet power is still in the system as the horn and hazards work with the car off, possibly indicating a faulty fuse or relay. The battery seems good, and had no problems starting the car. Keyfob battery is brand new as well. OBD2 scantools doesn't mention anything either. Could be a faulty ECU but no other symptoms show for that.

Only thing I can think of is a busted relay or fuse that stops the alarm system and keyfob from working at all times, and the lack of electrical power that keeps the door locks and dome lights from working when powered off.

I'd like to hear what everyone thinks before I bite the bullet and take it to a shop or worse, a local lexus dealer. Any advice would be greatly appreciated!

You have a couple issues here.

1. Old age of truck... MTF

2. A wiring issue.


1. Your door locks getting weaker--this is normal--not that it is good, but pretty normal. Two options here: Repair or Replace door lock actuators, or live with it. Since the only time you need to cycle the locks more than once or twice is programming the keys, and that can be accomplished by manually cycling the lock on the Driver door, this is pretty easy to live with for the fronts... The rear hatch lock is not physically connected to the rear key slot, so this is the same issue as the front locks--repair or replace the actuator--this is little bit more pressing as I have been locked out of the back of my truck several times and it was very aggravating.

2. As posted above, you likely have a wiring issue that will need to be chased down. Do the the dome lights work with any of the doors? If so, your likely culprit is the door switch. If not, I'd look real hard at the alarm system wiring as there shouldn't be an OEM component that shuts down those systems but still allows the truck to start. Also, verify that the dome light switches are working correctly--several of mine have to be finagled with for a bit to make them work right--20+ years of dust and driving has gunked up the contacts.
 
So after giving it some more thought and investigation, I narrowed it down to a constant power problem with the lc100 for the systems not being powered when the car is off and the key is removed. These systems are; Remote Locking System, Dome, Clock, Ignition Light, Door Courtesy Lights, Headlights, "Double Unlocking". Things that do work with the car off is the horn, the hazard lights, and the "key indicator" for the immobilizer.

Anyways, I suspect the reason this came about is due to either the AHC being removed by the previous owner, and messing with the wiring harness. The second suspicion would be the removal of a 2nd battery setup the previous owner had. I can't find any reason for it to be anything else as I've had no symptoms that come from a grounding issue, a short, or blown fuses/relays. I believe that someone had forgot to fix the wiring back to the original standard when uninstalling either the AHC electronics under the steering wheel, or forgot to fix it back to standard when uninstalling/installing a dual battery setup.

I'm leaning towards the dual battery setup, as it would make sense for the 2nd battery to be the primary source for accessories and the starter to be powered via the primary battery. This is all speculative and I would have to do some inspection for the previous dual battery setup, as I came to this conclusion at work today.

The only other possibility I could think of is if the ignition has gone bad, but I haven't had any other symptoms of a bad ignition since my car starts up normally.

Anyways, here are some similar forums that I found that have some of the same problems as I do or could provide some insight to the issue. I hope that these links could be insightful to others looking to help solve this annoying issue. I'll have to do more investigating once I find the time this week.





Regarding the issue of the door locks "losing power" throughout the locking cycle, I found a forum that indicates that I simply have worn/bad door lock actuator motors that need to be replaced or maintained, which leads me to believe it's a seperate issue to the constant power problem:
 
You have a couple issues here.

1. Old age of truck... MTF

2. A wiring issue.


1. Your door locks getting weaker--this is normal--not that it is good, but pretty normal. Two options here: Repair or Replace door lock actuators, or live with it. Since the only time you need to cycle the locks more than once or twice is programming the keys, and that can be accomplished by manually cycling the lock on the Driver door, this is pretty easy to live with for the fronts... The rear hatch lock is not physically connected to the rear key slot, so this is the same issue as the front locks--repair or replace the actuator--this is little bit more pressing as I have been locked out of the back of my truck several times and it was very aggravating.

2. As posted above, you likely have a wiring issue that will need to be chased down. Do the the dome lights work with any of the doors? If so, your likely culprit is the door switch. If not, I'd look real hard at the alarm system wiring as there shouldn't be an OEM component that shuts down those systems but still allows the truck to start. Also, verify that the dome light switches are working correctly--several of mine have to be finagled with for a bit to make them work right--20+ years of dust and driving has gunked up the contacts.

Thank you, I reached the same conclusion as you and many others. I'll be replacing the door actuator motors or possibly maintaining them if it's easier and cheaper. Do you know where to get the door lock actuators?

Dome lights work just fine with the car switched to "ON". As for the alarm system wiring, where do I start? I can't seem to find where the alarm system is.
 
Sounds like a bad relay, connector or door switch? Is the remote locking and alarm system stock? I had similar symptoms in my 99 LC when I bought it and it had an aftermarket security system fitted which had been wired in very poorly. One of the fuses in the left kick panel was blown (I think it was either the 10A IGN or 15A gauge) and the security system was wired over it. Truck still started and ran but no remote nor central locks anymore. After removing that mess and repairing all wires back to factory state everything worked again. While teaching the system new remote keyfobs I found out the front left door switch did not work very reliable, needed a couple attempts to get through the sequence. Still on my list to be cleaned or replaced.

Good lord, rewirring the harness sounds like a total nightmare. Do you know where I can find the security system, or guides on rewiring the wiring harness? Thanks
 

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