Apply Brakes - Reverse Light Illuminates

[VBdenny]

I had a situation where when I applied the brakes, the reverse light came on. In addition, the transmission did not shift properly. I complied information from others on LOC and made the neccessary repairs. The broken wire was exactly where I expected. A very easy repair in fact the most difficult part was removing the old electrical tape from the wire. I did not use a knife ssince I did not want to chance accidently cutting anything.

Here is the information I gathered. It is not organized in any particular order other than time. Attached is a PPT that I made while doing the repairs. If the file does not upload, email me and I will send it to you. Size is about 3.5MB vbdenny@myway.com

THE FOLLOWING INFORMATION WAS COMPLIED FROM PREVIOUS POSTS ON LOC

have 1992 LS400 v8.

Every time i hit the breaks, engine on or off.

The ® on the dash would light up telling me im in reverse gear.

I checked all the light bulbs they are all corect and all working.

Any suggestions?

I posted this message in a different thread. I think it could help a lot of people with low idle speed problem. So I start this new thread.

My car is 1994 LS400.

The low idle speed problem is so common among the earlier LS400s. It is very difficult to pin point the problem. I have experiencing the low idle speed problem for about 6 months. Whenever the car stops at traffic light or stop signs, the idle speed was very low, sometimes it was below 200. With AC on it was a bit better. There was a strange symptom, when the air humidity was high like raining, the problem went away. I did quite a lot of study on this forum about this problem. There are many many LS400s having this problem. And people did all kind of things trying to fix it, cleaning the throttle body, replace or adjust the throttle position sensor, clean the idle speed control vavle, etc. but still having the problems.

There is one article giving me a lot of hint. Here is the URL.

http://www.autoshop101.com/forms/h21.pdf

It is talking about the engine air intaking. In it, it mentioned the "Power Steering Idle Up". In short, the power steering draw quite a lot of horse power from engine at low speed. To compensate this power, it use the "Power Steering Idle Up". Basically it is a valve, it opens when the car is moving at very low speed or idling. It gives addtional air to the engine and keeps the idling up. The LS400 has this valve. If you open your car hood, you will see a thin hose from the air intake (right after the Mas Air Sensor) goes to the power steering pump, and another hose gose from power steering pump to the engine air intake, right above the Idle Control Valve. After many years, this valve stops working. It stops giving the addtional air to the engine. And I think it is the LS400 engine ECU programming flaw, when the engine runs at low idle speed, it is only programmed to control the Idle Speed Control Valve in addtion to the power steering idle up valve. It is not programmed smart enough to detect the low idle speed below 650, and to let the Idle Speed Control Valve to give enough air to raise the idle speed to 650. In short, the ECU can not handle the situation when the power steering idle up vavle stopped working.

The above is my analysis after the studying.

To fix the low idle speed is really simple. Just to re-connect the two hose I mentioned above ( one hose from the air intake (right after the Mas Air Sensor) goes to the power steering pump, and another hose gose from power steering pump to the engine air intake, right above the Idle Control Valve).

Here is the steps to solve your low idle speed problem. Refer to the attached picture.

1. Disconnect "hose1" from "nibbles1".

2. Disconnect "hose2" from the Power Steering Pump Idle up valve (this end of hose2 is not shown in the picture).

3. Connect "hose1" (the side just disconnected from "nibbles1") to the Power Steering Pump Idle Up valve ("hose2" just disconnected from it).

4. Connect "hose2" (the side just disconnected from the Power Steering Idle Up valve) to "nibbles1".

It is pretty difficult to disconnect and connect the hoses to to power steering idle up valve because there is not much room down there. What I did was removing the air filter housing, it will give you some extra room to work there.

After I did this, the low idle speed problem went away. Man, do I feel good every time when I see the speed right at 650 in front traffic lights? You bet.

You may ask some questions, does this cause any problem when this hose keeps sending air to engine all the time? I think no. Just think it is equivalent to your gas peddle, it simply give the engine a little bit more air when you drive at high speed, or you can think you lift your gas peddle a tiny bit since this hose give some addtional air. But I can bet you won't feel any difference. When the car moves at low speed, the hose suppose to open, so there is no difference here. Also this hose is right after the Mass

Air Sensor, so it won't cause any unmeasured air issue.

There is an addtional benifit by doing this. The LS400 also has a known problem, leaking Power Steering Fluid to the engin intake. The problem of that is also caused by the Power Steering Idle Up valve. By loop it back, you prevented this future problem.

I think the Toyora engineers should totally eliminate the Power Steering Idle Up valve. Instead, they should use the ECU to detect the low speed and sending the addtional air through Idle Speed Control Valve.

Attached Images

The broken wire was next to the hinge, if you look real close. you could notice right away. (White wire with black stripe). broken wire was due to lack of wire, ie

to short. (Factory defect i think)

Easy fix!

Thanks again to all who replied!

Troubleshooter.

The broken wire was next to the hinge, if you look real close. you could notice right away. (White wire with black stripe). broken wire was due to lack of wire, ie

to short. (Factory defect i think)

Easy fix!

Thanks again to all who replied!

Troubleshooter.

I'm posting this from the clublexus forum.

http://clublexus.com/forums/showthread.php?t=239568

Full credit goes to Jayjw for his post!

My car is 1994 LS400.

The low idle speed problem is so common among the earlier LS400s. It is very difficult to pin point the problem. I have experiencing the low idle speed problem for about 6 months. Whenever the car stops at traffic light or stop signs, the idle speed was very low, sometimes it was below 200. With AC on it was a bit better. There was a strange symptom, when the air humidity was high like raining, the problem went away. I did quite a lot of study on this forum about this problem. There are many many LS400s having this problem. And people did all kind of things trying to fix it, cleaning the throttle body, replace or adjust the throttle position sensor, clean the idle speed control vavle, etc. but still having the problems.

There is one article giving me a lot of hint. Here is the URL.

http://www.autoshop101.com/forms/h21.pdf

It is talking about the engine air intaking. In it, it mentioned the "Power Steering Idle Up". In short, the power steering draw quite a lot of horse power from engine at low speed. To compensate this power, it use the "Power Steering Idle Up". Basically it is a valve, it opens when the car is moving at very low speed or idling. It gives addtional air to the engine and keeps the idling up. The LS400 has this valve. If you open your car hood, you will see a thin hose from the air intake (right after the Mas Air Sensor) goes to the power steering pump, and another hose gose from power steering pump to the engine air intake, right above the Idle Control Valve. After many years, this valve stops working. It stops giving the addtional air to the engine. And I think it is the LS400 engine ECU programming flaw, when the engine runs at low idle speed, it is only programmed to control the Idle Speed Control Valve in addtion to the power steering idle up valve. It is not programmed smart enough to detect the low idle speed below 650, and to let the Idle Speed Control Valve to give enough air to raise the idle speed to 650. In short, the ECU can not handle the situation when the power steering idle up vavle stopped working.

The above is my analysis after the studying.

To fix the low idle speed is really simple. Just to re-connect the two hose I mentioned above ( one hose from the air intake (right after the Mas Air Sensor) goes to the power steering pump, and another hose gose from power steering pump to the engine air intake, right above the Idle Control Valve).

Here is the steps to solve your low idle speed problem. Refer to the attached picture.

1. Disconnect "hose1" from "nibbles1".

2. Disconnect "hose2" from the Power Steering Pump Idle up valve (this end of hose2 is not shown in the picture).

3. Connect "hose1" (the side just disconnected from "nibbles1") to the Power Steering Pump Idle Up valve ("hose2" just disconnected from it).

4. Connect "hose2" (the side just disconnected from the Power Steering Idle Up valve) to "nibbles1".

It is pretty difficult to disconnect and connect the hoses to to power steering idle up valve because there is not much room down there. What I did was removing the air filter housing, it will give you some extra room to work there.

After I did this, the low idle speed problem went away. Man, do I feel good every time when I see the speed right at 650 in front traffic lights? You bet.

You may ask some questions, does this cause any problem when this hose keeps sending air to engine all the time? I think no. Just think it is equivalent to your gas peddle, it simply give the engine a little bit more air when you drive at high speed, or you can think you lift your gas peddle a tiny bit since this hose give some addtional air. But I can bet you won't feel any difference. When the car moves at low speed, the hose suppose to open, so there is no difference here. Also this hose is right after the Mass

Air Sensor, so it won't cause any unmeasured air issue.

There is an addtional benifit by doing this. The LS400 also has a known problem, leaking Power Steering Fluid to the engin intake. The problem of that is also caused by the Power Steering Idle Up valve. By loop it back, you prevented this future problem.

I think the Toyora engineers should totally eliminate the Power Steering Idle Up valve. Instead, they should use the ECU to detect the low speed and sending the addtional air through Idle Speed Control Valve.

Thanks to this and several other posts on this subject which helped me tremendously. I thought it only fair to share my success and methods to maybe help the next in line. My 94 LS400 started blowing puffs of white smoke on start up and continuing to do so while at idle but not as bad. After reading many posts, I decided it was either the air control valve (idle control valve) or one of the coil packs. I bought both parts. Air control valve I got for $80 at a toyota dealership (part# 17630-16040) and the coil pack was $39.99 at Autozone (part#C903 i think). Got home, pulled plugs on each side to check for unburnt gas which would tell me it was the coil pack. All plugs looked fine. For those who haven't pulled the plugs before, they are in the middle of the valvle cover. To get to them...remove the plastic piece towards the front of the engine, the one between the valve cover and the intake and the one running down the middle of the valve cover.(this is for the driver's side, passenger side is the same but you must also remove the air filter and tubing leading up to the engine) You will need a 10mm socket for most bolts, a 5/8 spark plug socket, and a 17mm wrench for the air control valve.

The air control valve can be located from pictures on various posts. I found it by following the two small hoses leading from the intake down to it. It is screwed into the bottom of the power steering pump below the power steering pump resevoir. I first tried to access it from the top only to have a difficult time and almost started removing the power steering pump resevoir. Don't bother with all of this. Take the large plastic under belly completely off with the 10mm socket and access it from the bottom. Find a short 17mm wrench and a good light. BEWARE...fluid will pour out on you when you get the valve out. It covered my right side.. =) Lovely feeling at 2am with work closing in at 8am and no sleep. Anyhow, the valve is a simple unscrew and replace then replace the rubber hoses. You might need pliers for the hoses, I pulled them off and reattached with just my hands.

PS. I knew it was in fact the air control valve as when I removed it, the center piece creating the valve close off fell out and there was fluid in the hoses leading to the intake.

Good luck. Hope this helps the next person.

Nikk

You are looking for an air control valve. It is mounted on the passenger side of the PS pump and is downward facing in about the 7:30 position. You can get the part from Toyota, but I found Irontoad.com cheaper by about $20. Good luck!

I believe I remember a post something like yours where the problem is caused by a broken ground wire in the trunk hinge area. I believe some wires run through the drivers side hinge and that it is a common problem to have broken wires in that area. I may be wrong but you might check it out.

Curt