Since the SC doesn't have drive-by-wire (DBW) on the second generation body (or 1st depending on your country), the old fashioned throttle cable is used to open the throttle linkage butterfly valve to allow the engine to pull in more air. In this post I'll review replacing the cable. In the rare event it needs replaced, swapped for an automatic to 5-speed conversion, or GTE engine swap, don't worry as it's not a huge task. You will need a few tools (listed below) to get this job done Note that in 1998-2000 years the throttle body designed changed with the addition of a VVT-i head so the part numbers in this post may differ for 1998+. For my situation, the actual braided wire inside the cable casing was damaged during an engine transplant. The wire was crushed when engine was pulled from the bay and developed a significant kink which appeared to slightly affect throttle response. I'm not exactly sure how much affect this had, but it was bent enough to create some slack before the pin actually moved despite how stiff the cable is, so I decided to change it out.
Original cable with significant bend.
There were some side benefits to doing this procedure. One, I got to see how the wire was routed through the firewall and how it attached to the gas pedal. I had never seen this before and thought it was significantly more complicated than it actually is. It's hard to visualize that the hole in the firewall is so near to you while you're sitting in the driver seat. Also, the part is "new" despite probably sitting on a shelf for years and was less dry and stiff then the one I removed. The new unit's cable slid in and out of the housing much easier, which may change the throttle feel in some minute way. I suppose it's possible to oil/lubricate the existing one, but I'm sure this is not a part that needs replacing or maintenance under most circumstances. However it appears this is a common maintenance task on motorcycles with tools designed for this specific task, so it can't hurt. I found a replacement part on Rockauto on sale during a wholesaler closeout for a very low price of about $25 with tax and shipping. I was suspicious initially because the part was branded as a Beck/Arnley part and I thought that maybe there might be some key differences in build quality or length. What I discovered was quite the opposite. The part was 100% exactly the same including markings, cable position, and coatings on the adjustment bolts. I suspect that either Beck/Arnley purchased these from Toyota during initial production for later resale, or they made all of them to begin with (likely under a parent company of some sort). No matter the history, the part is exactly the same. (Edit: it appears they buy from Toyota and later resell.) Here are the part numbers for the manual transmission cable and approximate prices from Beck/Arnley and Toyota. If you're looking for the automatic transmission part number please scroll to the very bottom of this article. I did mention the GTE swap earlier - you would likely need a Supra or Aristo, etc. throttle cable and I do not have those part numbers. Genuine Toyota SC300 Manual Transmission Cable P/N: 78180-24070 - $65.00 + depending on dealer Beck/Arnley P/N: 0950577: $25+ on sale
Replacement box.
Gas pedal end showing firewall mounts and ball weighted clip for pedal attachment.
Replacing the cable is quite simple and hardly daunting, but requires some dexterity and flexibility to maneuver under the footwell. Tools required:
10mm socket and ratchet with short extension.
Flashlight
2x 12mm open ended wrenches (for throttle body side mounting clip)
Needle nose pliers, or small tip screwdriver, punch, etc. to push throttle cable head/yoke?/pin out of linkage.
Paint pen / camera to note current cable adjustment nut position.
First, open the hood and remove the cable from the throttle body linkage. Rotate the linkage/spring all the way back as if you were opening the throttle body fully and make sure to hold it tight or have someone else hold it while you pull the cable towards you and rotate the throttle cable back and upwards. Then use the small pliers/screwdriver/punch/etc to push out the cable head from the guide slot towards the cabin/rear of the car. If you get stuck here, just breathe, take a closer look at how the pin inserts into the linkage and try again. Do not let the throttle linkage/spring snap shut with your fingers near it - this will cause injury. Slowly release it. Mark the position of the cable locking nuts on the guide slot (behind the throttle body.) Use the two 12mm wrenches to loosen the outside nut in the cable guide (the inside nut is typically glued/locked to a fixed position) and pull up to remove. Note: earlier year SCs had a different style throttle body with an outside spring return. Later years have a wound coil spring, but the procedure is still the same. Inside the car: To make things easier, move the driver seat back to the farthest position, raise tilt steering wheel to high (or leave key out of ignition if auto-retract is on) and find a comfortable position to reach under the gas pedal. There's not really an easy way to explain how to remove the weighted ball end (shown above with the blue plastic clip) from the pedal. You need to see it and press the clip tabs, rotate, and once you take a look it's becomes apparent what you need to do. Remove the two 10mm bolts for the firewall mount.
Pull entire throttle cable unit from inside the car out through the firewall. Reverse to install; tighten mounting bolts near gas pedal, hook cable to gas pedal, lock cable in guide and push cable back into throttle body linkage. Before attempting to drive, leave the engine off and press the gas pedal a few times to make sure that it is not binding or getting stuck. ------------ Automatic transmission accelerator cable part number (genuine Toyota OEM confirmed for all years 1992-2000) : 78180-24131
7/10/15 Editor's Note - I've since learned much about the process and have come up with some more possibilities. The procedure outlines below is not recommended as there may be heavy amperage draw on the door lock wires- albeit very, very short and probably won't cause an issue. However, I have been getting help on coming up with a better solution involving a PCB. IF you want to try doing this anyway, the most important thing to note is that the diode size is too small for this application, step up to a 3A or higher diode. 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
How this works: 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)
What's the downside? 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.
Please note that this is was done on a 1997 SC300. Fortunately there are a handful of options for upgrading the brakes on the SC model cars. The two most common options being the Supra TT steel calipers and the 1995-2000 LS400 aluminum calipers, followed by custom Corvette calipers and 8 pot calipers from eBay. I won't discuss pros and cons between these options as I'm not technically versed in the dynamics of braking. I chose the LS400 caliper option for a couple reasons; cost, weight savings, and ease of installation. A set of used LS400 calipers with pads and rotors was a very affordable $150. Compared to a set of increasingly difficult to find used Supra TT calipers at over $350 ($800+ new) this is the best option. The Supra TT calipers are heavier although I'm sure are there are pros and cons to steel calipers beyond this article. Do these brakes provide an actual upgrade to stopping distances? I'm not sure. The stock brake system can lock up your wheels so the ABS and tire systems are the main factor when trying to stop from full lock. What you'll gain with this upgrade is a more solid initial pedal bite (*Update 2015 - not so sure about a better pedal bide, keep reading), better fade resistance during long hard braking and aesthetics. There are a few caveats that must be taken care of prior to and during the installation if you decide to go this route. Update 2015 - I believe the LS400 caliper has large fluid channels which causes the initial soggy pedal feel, but I'm not sure. The braking ability is retained but there is a slight increase in pedal travel. There may be a few causes for this. One is that the master cylinder may not push as much fluid through, or after years of use it has set in and has a wear pattern that only allows a certain amount of fluid in based on the old caliper channels. I'm not sure how to explain this, but in short, a new master cylinder may solve this; either a larger booster from an LS or Supra (although the mounting brackets may be different,) or a factory sized SC replacement. The other possibility is a small amount of air trapped in the system somewhere. This is why bleeding all 4 calipers is essential, so this possibility is ruled out. First off, the most important requirement is having the proper size wheels. There may be a more technical term in the world of wheel vocabulary but they must be "high disc" or "high clearance" wheels. The factory 1993-1998 Supra TT (NOT the non-turbo) 17" wheel is a direct bolt on for the SC and works with the Supra TT and LS400 calipers without spacers. The 1995-2000 LS400 wheels may be another option, but these are 16" and not an upgrade in terms of wheel performance. It may be handy to carry one of these as a spare if you have done caliper upgrades on all 4 wheels since the stock spare won't fit over these calipers. If you're only doing the front wheels, then you should be fine as you could swap the rear wheels to the front although this is more tedious in a side of the road emergency flat situation. The next requirement is the trimming or removal of the stock brake dust shield (A.K.A splash shield or backing plate). I don't recommend removing it. This directs airflow, keeps debris, water, and brake dust away from the braking system and parts of the body. It's there for a reason although the car will still work without them. About 1" from the top and sides must be removed with metal shears to clear the rotor. It is possible to swap the matching LS400 brake shield although it requires some cutting as well. If one wanted to really find the balance between cutting and replacing the shield, an option would be the Supra TT brake shields which might still require some cutting. I have not confirmed this myself but it seems to be the most logical path since the Supra TT and SCs share so much in suspension design. The last requirements are the trimming of the brake caliper body behind the mounting area, the removal of the guide pin on the brake line, and bleeding the brakes. The LS400 caliper has an area on the underside which hits the knuckle near the two 17mm mounting bolts. About 1/8" must be trimmed off so the lower bolt can fit. I will explain more below. Also, the brake hose line has a guide lock pin designed for the SC300 factory caliper. The distance between the fluid banjo bolt and guide pin is about 1/4" longer on the LS400 caliper. You will either need to swap out for LS400 lines, go aftermarket braided or simply squeeze the guide pin with pliers and remove it. I have read that LS400 lines are shorter and may be too tight at full wheel lock, but I haven't verified this. The best performance option is either new OEM lines, or stainless SC lines, not LS lines. Bleeding the brake lines is the very last step. Initially I couldn't find the bleeder valve on the LS400 calipers since they are covered by a rubber boot! Below are the steps I took to do this low cost, effective brake upgrade. What you need: Complete LS400 caliper set including pads, pins, and mounting bolts. You cannot reuse the SC300 caliper bolts. The LS400 bolts are shorter and designed for the caliper. LS400 rotors 14mm open end / box ring wrench 17mm open end / box ring wrench 14mm socket 17mm socket 21mm socket Air compressor (if available) + impact wrench + grinding tool Breaker bar or long ratchet Philips/Flathead screwdriver just in case Torque wrench Metal shear cutters Brake fluid Brake cleaner spray Wire brush Someone to help with the bleeding process or a pump tool Safety goggles especially if using a grinder.
I assume no responsibility for any mistakes or errors you make.Safety first! 1. Put your car on a stable surface and put it in park or first gear with the e-brake on. 2. If doing the passenger side first, turn the steering wheel to the left about 75% of the way so you can easily access the bolts on the back of the brake. 3. Loosen the wheel nuts with the 21mm socket, but do not remove them, then jack one side of the front up, then remove the wheels. 4. Slightly loosen the brake fluid line on the caliper with the 14mm wrench or socket depending on your available tools. Do not let any fluid out or open it all the way. The purpose is to loosen the bolt so when it's time to swap the calipers you don't have to struggle to find a point of leverage with the caliper off the hub. 5. You can choose to disassemble the caliper and it's bracket here, or just remove it in one piece. If you disassemble it, take the two 14mm wrenches and pull the installation bolt. Remove the caliper and place it on a steady surface so the flexible rubber brake line is not under tension/hanging. 6. Remove the caliper bracket by using the 17mm socket on the two bolts in the back. Please note that if your car has been sitting for years and the caliper bracket has not been removed, they may be rusted in at the thread end of the bolt. An impact wrench will not get these off if that's the case. You will need a breaker bar for the leverage. 7. Tap the rotor with a mallet around the center face (not the edges or face of the rotor) or use the rotor removal pinholes to push a bolt through them to get the rotor off. Some cars may have rotor lock screws that need to be removed. Depending on how long they have been on this may require some effort from rust buildup. 8. Now that the rotor and caliper are removed you can take the LS400 rotor and mock fit it to the wheel hub. Note where you need to trim the dust shield. About 1.5" of metal will need to be sheared around the circumference of the shield. Below is a picture of what I took off with the shears. You may take more time to get it exact if you wish. Use a metal file to soften the edges. You don't want to reach in here for the next rotor change and slice your finger open.
9. Take brake cleaner spray and a wire brush and clean the surface areas of the hub and wheel studs. 10. Take the LS400 caliper and mock mount it with one bolt in the top. Remember the bolts are put in from the back side!
You will see the lower bolt hole is about 1/8" off and won't line up. This is because the caliper has a fin that touches the wheel knuckle/spindle at the top.
11. Remove the caliper from the wheel hub and take your metal file or air file tool and grind the corner of the caliper shown above. Be EXTREMELY careful and only take about 1/8" off, or just enough to clear the spot. Contrary to what's shown above, I accidentally ground the side of it with the air tool - you do not need to do this section. Only the top where it touches. Put the caliper back on to test the fit again. You should be able to put both the upper and lower bolts in with ease. But don't tighten them down- the rotor still has to go on. 12. Take your rotor and spray liberally with brake cleaner and a lint free rag. Place it on the hub and press it in firmly. Take one wheel nut and screw it on to keep the rotor in place. Double check to make sure the dust shield is not rubbing on the backside of the rotor. If it is, trim again or fold back just enough. 13. Put the caliper on and screw in the LS400 bolts. If you haven't already taken the rubber line off the old caliper, do so now and quickly swap it over to the LS400 caliper.
13. From what I have read (not confirmed by me) the 1998-00 SC300 received the same caliper setup as the SC400
Please note these numbers are for a 1997 Federal specification (not sold in CA) SC300 with a W58 manual transmission. Some parts may be shared across all years, but you will need to contact your parts dealer or catalog with your VIN to be accurate. Drivetrain Flywheel bolts - 90910-02103. You will need to order 8 bolts and they cannot be reused if the flywheel is removed. Cost is ~$7 per bolt. Suspension Front shock absorber - 48510-29505. Cost is ~$65 each. Electronics Black rear cupholder (by the shifter, not the one by the radio) - 5562024020C0. Cost is ~$44. Body New revised headlight with projector change - 81523-24045 (driver) 81513-24045 (passenger). Cost is ~$350 per headlight. Interior e-brake leather cover. I do not have the part number for the different color options. The P/Ns could be one of the following. I don't know the difference. 46243-24030-05 46243-24030-03 Rear seat belt cover for black interior. This is the surround that goes where you plug the seatbelt in. - 7331524011C0 (Right) / 7331524011C0 (Left) - ~$15 each.
I've created this to serve as a journal and help guide for anyone with an SC300 looking to basic repairs, reference part numbers, aftermarket projects, etc. Currently I have a 97 SC300 5-speed (Federal, not CA spec) and have done many projects on it, from basic stuff like brakes to a nitrous system.
