Boy, what a project this has been.
7/4/15
First off, a little history.
We basically have three generations of the SC, but when it comes to the door locks, the generational change wasn't sequential. In those generations, only the last series from 1999-2000 had flashing turn signal/hazard lights synchronized to the piezo ("buzzer") beeping noise (added in 1995) when the remote key fob locked or unlocked the doors. The 1998 year saw big changes in the engine, but unfortunately the flashing lights weren't added until 1999.
The 1992-1994 models do not have a beep or a light flash. The wireless ECU was not designed for this. In 1995-1998, a small piezo speaker mounted in the driver side front wheel well, close to the door hinge, was added to notify the driver that the car was locked (one beep) or unlocked (two beeps), yet, still no flashing lights. The piezo buzzer is controlled by the wireless door lock ECU which is located in the rear pillar of the back passenger seat behind a panel.
In 1999, Toyota added the flashing light feature in conjunction with the buzzer like most other cars of the generation. This year saw a change in the wireless door ECU itself, which added 12V line out signal to likely trigger the turn signal relay in the driver side kickpanel.
So here's the problem and question. Without a dedicated 12V out on the wireless ECU, how do you get the lights to flash on the older cars? For some owners, this may mean getting an aftermarket alarm system. This whole post is useless if you have a modern alarm system with 12V output triggers that do something like honk the horn or flash the headlights when you lock and unlock. However, if you just have the factory alarm you need to rely on a 12V trigger from the door lock motors, not the ECU.
Now to make a point about my inexperience with electronics and schematics, I am not qualified, I'm just curious and slightly driven (sometimes). There is probably a better and more proper way to do this project. A seasoned car electronics person would probably find my method strange, but it works.
In this project's history, I started out thinking about a way to do this and actually imagined the correct way in the beginning, but didn't really have a grasp on the electronic details of how to complete it. I figured that there probably wasn't a direct signal from the ECU to grab to trigger the lights, but that I would have to find a 12V source that triggered when I unlocked and locked the car. This would be the door lock wires. However, I thought to myself "well, when I manually lock the doors with the power switch in the door panel, won't the lights flash?" that turned out to be the actuality, but I'm OK with that. You can still manually unlock the doors if that is unacceptable. The reason is that when you unlock with the power switch, electricity has to unlock both sides of the car. Again, manually flipping the switch by the handle doesn't affect anything, so there's always that option.
About halfway through the project, I thought I could possibly trigger a 12V horn /car relay with the piezo beeping signal. This would be perfect- right? One 12V pulse for lock, and two 12V pulses for unlock, just like what you hear, and you would get the corresponding flashes. However, upon inspection of the buzzer in the wheel well, I found there are two wires - black and red like you would expect. I thought this would be ground and positive, but actually, it's one wire for one pulse, and the other for the two pulses. Another possibility may be that the piezo is designed to beep twice with 5V and once with 3V, but I'm not sure. This is a very simplified, sort of stone age solution in my uneducated opinion because the wireless door ECU could have been designed to send two pulses out with solid state electronics or something depending on the lock or unlock condition. Maybe there's another reason for this, who knows? Like I said, I'm no EE.
Back to why the piezo is a bad source - it's only 5V. this isn't strong enough to trigger a 12V relay to power the lights. So after pulling off the wheel, taking the fending lining out and getting dirty, it was a dead end. A smart electronics expert would probably figured out a way to step up the 5V signal, but that may have been more work than is needed considering you have two separate wires for lock/unlock.
So we end up back at the power lock wires in the kickpanel. I stuck a multimeter in each pin of the door kickpanel, locked and unlocked the doors and found the two wires that get 12V when the car is locked or unlocked with the remote or power switch. They are larger than the others, presumably to carry the amperage to trigger the lock solenoids. On my 1997, one is a light green, and the other is teal faced opposite each other.
After finding a 12V source for lock/unlock, we need to find where to send this signal. After searching around for ideas online, I ran across someone who did this to an older BMW 3 series. They sent the 12V to the emergency flasher switch in the center console. Basically, when you press your hazard button, it sends 12V to the turn signal relay, or possibly the relay sends 12V out to the lights wires in the switch. I'm not entirely sure how it works. I thought this would also work here since the switch is relatively easy to access. The SC hazard button has 8 wires coming out. To access it, you'll need to remove the console trim by removing the shifter cover, the cupholder, and unscrewing the philips screws. Unclip the climate / radio controls and the hazard wire harness. In my 1997, the top two wires on the right, with the clip pins facing you (not the wire end) power the left and right side parking lights. Another wire triggers the relay itself, but I chose to tap into these two separately. Again, probably my novice experience doing the planning here.
What you'll need:
- Wire crimping tool
- Quick splice female and male ends
- A few feet of wire
- 50+V and 3A or more diode (the diode below is rated too low)
50V Diodes (radio shack part # 276-1101) <-absolutely required - see below.- Light (flashlight or daylight)
- About an hour or two.
- Any battery less than 12V, like a 9V or AA.
- Soldering tools + heatshrink
Since the 1998 and earlier cars don't have a dedicated 12V signal out to trigger lights or the horn, by tapping into either the lock or unlock wire in the driver side kickpanel, you can access a 12V signal. This pulse can be used to turn on the front and rear turn signal/hazard lights when the car is locked or unlocked. Since we are also tapping into the emergency flasher, we don't want electricity flowing back to the door locks or the horn/hazard relay system when the hazard switch is pressed. This is why diodes are required. You will blow fuses without them.
A note about the diodes - I didn't know this at the start of the project and wondered how I would prevent electricity from going back from the emergency switch into the door locks. This is what a diode is for. The diode prevents electricity from flowing in a desired direction. think of it as a check valve or a one way valve in plumbing. The diode has a marker on the body which allows forward bias, meaning the 12V signal only goes into the lights, not backwards into the door lock.
PLEASE forgive this absolutely crude drawing, but it's the general idea.
(Left and right are backwards in this diagram)
Although you can have this work on unlock and lock, I chose to only wire it into the door unlock wires. For one, if you start driving and use your power locks your hazard lights will flash. This is distracting to other drivers. You can always manually unlock / lock the switches however.
The second reason is more of a logic thing - you're more likely to want to use a visual cue to find your car in a big lot or something, and you would normally be attempting to unlock your car. Now you have a visual aid.
Third reason is that you will need more diodes on the lock wire to prevent a lock/unlock loop from occurring - if you unlocked the car and had the wires tied together, the 12V would then immediately lock the car again and possibly blow out the relay or a fuse.
Procedure:
First, you'll need to create a harness by soldering the diodes inline to your wire clips. The diodes MUST go with the silver marking facing the wire spade/clip. This allows electricity to flow to the light wires, but not the other way. Take your wire, strip off enough to go into a clip and cut it in the middle to make room for the diode. To simplify things, you will crimp two of the leads into one spade. See the pictures below.
Lay everything out, your clips, soldering gun, multimeter and battery.
Solder the diode inline with the silver band facing the clip.
Before you apply solder, wrap the diode leads and test to make sure 1) the diode works, and 2) that it's installed in the correct direction. Put your 9V battery on one end of the wire and use the multimeter to test that you get 9V on the other end. Now flip it around and put the 9V on the spade side. You should not get any reading on the open wire end.
Wrap the diode leads around the exposed wire, then apply solder.
Seal with heat shrink.
How wires should look. Notice we have one incoming wire with a diode, then in that clip, is the other wire attached together, which has it's own wire, diode (for the other signal) and clip to the other light wire.
Verify that the top right two wires activate the left and right turn signals. Do this either by referencing the correct year factory electronic service manual or by applying 12V to the pin - you should see the turn signal indicator light up. Take your new wire and run it behind the radio panel and under the driver side floorboard with the other wires. Be sure not to allow it to get tangled in any of the pedals. Continue running it over to the blue connector kick panel area for now. Now, look back up to the hazard switch and see the above photo.
Using common quick-splice and male wire end connectors from the auto parts store, I tapped into those two wires as shown below. The right side light wire is green and yellow and the left is green and black(?).
This is how the quick connect should look.
If you want this to work on both lock and unlock, you will need another diode inline at the kickpanel harness to prevent simultaneously locking and unlocking or popping a fuse or burning out a relay somewhere. I didn't bother with this, so I haven't thought it through completely. Do at your own risk. If you want it on lock, just switch the wire to the lock wire at the blue harness.
How it could have gone better:
What drove me nuts about this method is that by using the power unlock in the door, the lights will flash. It MAY be possible to find the 12V trigger further up the line closer to the wireless door lock ECU in the back seat and tap there. It still may loop all the way back to the power locks so that may be a futile effort. The other option which I'm currently experimenting with is having a normally closed relay inline with the newly run wire, it will prevent 12V from coming out of the door lock to the hazard switch when the car is on, and when off, the 12V signal to flash the lights will pass through.
Another minor thing that the flash of the lights is somewhat short since the lock pulse is short. I think on modern cars they have some sort of capacitor or electronic control that fades the lights out for a longer duration, maybe half a second instead of a quarter second. I have yet to test, but instead of tapping into two wires, I can use one of the other emergency harness wires which triggers the relay for both sides. *Update* it's not possible to trigger the relay without jumping the wires together in the harness, and does not provide a longer 12V pulse. This may provide a longer light flash. A capacitor may be the only option.
That's all for now.
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