Hello everyone, I am new to the forum. I recently purchased a 1999 Lexus RX300. I took it to the Lexus dealership yesterday to get all my fluids changed, and also for them to look at a noise coming from my climate control system.

The were testing a servo motor behind the glovebox and had to disconnect the battery. After I picked the vehicle up the problems started.

Everytime I shut the vehicle off, the alarm starts going off after 10 seconds. I have to unlock on the fob to disarm. Then lock. And everything is back to normal until I drive it and shut it off the next time.

a couple things I noticed since this started,
1. I had a light on the dash yesterday for brake light being out. I checked it out and sure enough my 3rd brake light was out. Not sure if related or a crazy coincidence happening immediately after. But when I drove my kid to school today the light was no longer on my dash, haven’t checked if the light physically is turning on though yet.

2. everytime I started the vehicle before; the antenna would raise, and when the vehicle was shut off it would immediately lower. Since I got it back from the dealer yesterday the antenna doesn’t lower for around 30-40 seconds now after being shut off.

i dropped vehicle back off at dealership this morning. Their tech looked at it for 5 mins and said he couldn’t figure out why. I left it there for the day but I’m doubtful they will find a resolution. I scoured the internet for hours last night trying to figure out a solution. I seen a half dozen other posts in various places including this forum where people had the same problem, but no one had a solution.

please please please help!

 

Congratulations.

It is a fine vehicle but considering the age, if you keep going to the Lexus dealership. the maintenance costs will quickly go beyond the street value of the vehicle. So learn DIY or find a cheaper place for maintenance/repairs.

Hopefully you have 2 master keys [and a valet key would be nice, and a wallet key would be nice]. There are certain security service items that require both keys. So check with the mechanic if you need to bring the second key to the shop.
[Note if you have only 1 master key, get a duplicate made and register it with the ECU.]

1. The brake light fault gets activated only when brake is applied at least once after starting. The high mounted brake light bulb socket usually develops a problem where it gives intermittent connection, so clean the socket and put electrolytic grease.

2 ... no suggestion. Maybe the mast is bent. Lube it lightly. Too little will not help and too much will attract grime. At the end wipe it down. WD40 may make things better temporarily but at the end it removes lubricant.


Salim

 

the dealership had it all day. Couldn’t figure it out. Didn’t charge me.

i tried the security system override with the wire in the hood latch sensor to make it think hood is always open. Worked first time then got home and alarm went off again.

i told dealership about the keys stuff I have 2 master keys and a valet key. They had no clue what I was talking about and said they wanted to take all door panels apart to look at actuators. I’m lost on next solution

 

Lexus dealer couldn’t figure it out all day. Didn’t charge me for it. I mentioned the keys being used to reset the system. They had no knowledge as it’s too old and say they have no training for the older stuff. Nor do they have resources to find these things out apparently.

 

It could be wording here, but if you try to make the sensor think the hood is open, the vehicle will not go into "secure mode". If the sensor is bad [first you must verify it] you make do the appropriate bypass to fake the controller that it is closed.

With opportunity cost of $150+ per hour at dealership, I don't think that they will be spending a whole day. If the history is known, one can diagnose lot better. There can be an actual problem and first gen RX has some gremlins in the software. Removing battery power for 20 min, eliminates the gremlins. You will loose all/most of your radio-seat-glass setting.

Well trained & with experience RX300 mechanics will be hard to find. Look for independent Lexus/Toyota repair shops. Be prepared to spend 8hrs x 100 ~ $800 + parts.

If you have other options like leaning on the dealership [that is if they sold the vehicle to you] keep demanding a fix or take it back.

Lastly [my personal opinion here] the alarm system is pretty lame. The only real/effective thing is the imobilizer. You can investigate in removing the alarm system, but be careful as it can lead to parasitic draw as the vehicle computer will be awake.

Salim
PS: I am going by memory .. long time back the dealership instructed me over the phone to insert one key in the ignition and remove it and then insert the second key and remove it. Was that accompanied by brake pedal-press/door-open-close, is something I don't remember and even if the process was related to alarm [80% probability it was].

 

so I originally brought the vehicle Thursday morning to have all my fluids done. Engine cleaner they recommended + new synthetic. Transmission flush & fluid, new front and rear diff fluid, new brake fluid, new coolant. Plus they diagnosed the sound coming from climate control which started all these issues. First day costed me nearly $1300.

took it home at end of the day and immediately had issues, was there first thing the next morning. They brought it in and had the tech who worked on it the day before on it from 8-12. Then after their lunch the shop foreman was on it from 1-4. So they did spend a decent amount of time on it. (Apparently, could be lying but they gave me rides home & back also)

when I came back the service manager said I can’t even charge you we couldn’t figure out what’s wrong. Something must of got triggered when we unhooked your battery yesterday.

So I took the vehicle home, first thing I did was unhook battery for 30 minutes. Soon as I touched terminal to battery again to give the vehicle power the alarm was going off lol. Shut it off with the fob, everything worked as normal. Started vehicle. Shut it off, 10 seconds after the alarm is going again.. great.

so I found a thread on here called defeating the rx300 security system. With unplugging connection by hood latch and looping a wire in the plug from one end to the other. Did that. Started the vehicle and shut it off. Magically had no alarm! Success I thought..

then drove it 30 mins later to a friends house. Shut it off and 10 seconds later its alarm is going off again.

last Night I ordered all 4 door actuators, will replace and see if that helps.

im lost on next solutions. Where I live I don’t know if there’s anyone who’d be competent on working on it, that’s why I took it to dealer originally. I brought the vehicle from out of province because most of them are rusted and super high km. I got a 1999 with 140,000 kilometers only. Looks showroom condition inside and out. That’s why I wanted to make sure everything was up to spec so it would last forever. I went from a 2016 Audi S7 to a 1999 Lexus rx300 lol. I didn’t want the German maintenance anymore and now I can’t get the Japanese reliable car to cooperate currently lol.

if you have any resources for a proper key procedure please let me know. I don’t mind paying for anyone’s time who can help me with a real solution.

 

Without proper diagnosis, imho you are grasping for the proverbial straws and on the journey of throwing parts in the hope of a fix. Similarly you can not count on a fix that worked for another person will apply in your case.

Some one has to look at the circuit diagram and then trace the signals. Due diligence is required.

If you can lock/unlock and the dome light turns on and off with door open/close then the likelihood of bad actuators is extremely low.

Salim
PS. Flush of transmission is not recommended.

 

You're going to have to work your way through this. Search for "RX300 diagnostics pdf" and turn to page DI-443 Theft Deterrent System troubleshooting

 

thank you. I did read through this, yet nothing comes up related to my issue surprisingly. Also still trying to find the procedure to reset system with keys. Nothing is mentioned in that section.

 

The symptoms are very strange. Why would it arm and go off in 10 seconds? What is the red light doing?
I tested mine. I left the window open and exited the car.
Red light is blinking. Alarm is not engaged, I can reach through the window and unlock the car from the inside with no alarm.
Locked the doors with the fob. Light is solid. I can unlock the car from the inside with no alarm.
Locked the doors with the fob and waited for light to go from solid to blinking, about 30 seconds. If I unlock the car from the inside the alarm goes off.

 

The 30 sec delay for 'secure mode' can be expedited by double lock action [press the lock button twice with minimum delay] on the keaton lock, lock.

Salim

 

I had similar issues with our RX 300. The alarm issues were because I disconnected the drivers door power window switches without first disconnecting the battery.

Some combination of disconnecting the battery and the switch panel resolved it, I think. This was years ago so it's hard to remember.

The third brake light seems to be a common enough issue. The bulb socket actually gets worn out. I had to replace the entire bulb socket. If I recall correctly, I probably had to wire nut or solder on a new bulb socket. Replacing the entire socket resolved the issue.

 

I did disconnect the switches all around to switch to silver trim from the wood grain a few weeks ago. But had no alarm issues until dealer disconnected battery. Did not use new switches. Just replaced trim top plastics

 

Try this:

Insert master key1 in ignition.
Take it out.
hop 2 times [just kidding]
insert master key2 in ignition.
Take it out.


The above is what I can best recall. I could be missing some steps but .. hey it is simple and easy to do.

Salim

 

instructions unclear

broke ankle during second hop

😂 lol.

I will give this a shot ASAP. I might have another issue to solve first. Seems the other master key isn’t programmed or needs a new battery in fob.