Disable or bypass the headlight leveling sensor?

Here is a link to a post with a .pdf on how to repair the sensor. It is important to keep this working or your HID's will blind oncoming drivers. The sensor allows the level of the headlights to adjust to different loads and terrain. Please think about the hazzard you create by disabling or bypassing the sensor...

Headlight level sensor corroded? | PriusChat

 

Are you mechanically inclined?

 

I bet you can find a sensor at a junk yard for alot less.

 

I Just finished a "bypass" of the sensor on my 2006. I had problems for years (before warranty expired but dealer was clueless & never made not in service history so ... no 'joy' there from the dealer or Toyota).

When I finally pulled the sensor it was, as stated elsewhere, "toast." So, i looked into the service manuals. I found how to check the sensor. Using this information & a multimeter, I realized that:
pin 1 (SHG) is the ground
pin 2 (SHRL) is the variable output to the "Headlight Beam Level Control ECU" (reads sensor & then adjusts headlights)
Pin 3 (SHB) is a constant voltage of 5 volts
See uploaded file: : LI-Page68 Inspect Rear Height Sensor

Using the above, as mentioned by others, a rheostat could be used. I found it easier to use the existing housing and make my own fixed voltage divider.

I removed the center piece with the two springs attached to make room for my fix. (and also to isolate the traces on the cover even though the traces were mostly gone).

I soldered two 1 KOhm resisters in series (connected them end to end resulting in a straigh line). I cleaned & prepared each pad for soldering.

I positioned the resistors in an arc around the edge inside the sensor so I had one end on oneoutside pad and the other end to the other outside pad. Then I soldered them. (ie: one end to each of the outide pads where the springs would normally go inside the sensor).

Then I took a wire and connected it from the where the resisters are connected (to the junction of the two resistors thus making a "T"). The other end is connexted to the middle pad. (best to use a wire with insulator for this wire).

Put another way: I had a rounded horseshoe shape with a wire from the middle of the "horseshoe" to the middle pad with a resistor between the connection in the middle of the "horseshoe" and each of the outside pads.

What this does is divide the 5 volts from pin 3 (SHB). The middle pad gets half the voltage or 2.5 volts.

Ten adjust each headlight as needed. The voltage is fixed because the variable function of the sensor is eliminated so you can use this as a temporary solution untill you can get a repalcement part at a reasonable price. Just remember that you mus be aware that a load in the back of the vehicle will result in the headlights being aimed higher and will cause a problem for oncoming trafic.

As an additional problem, I also had pin #1 break off in the connector and this was another problem:

 

opps, hit the wrong key .... may be some typos above, will try to fix any later as in rush as usuall.

To continue with the broken connector issue ...

I took some WD-40, some baking soda, a couple picks and small needle nose plyers. I cleanded the connectors up as much as possible. Then I worked on the connector with the broken peice in it. (half of the male pin from the sensor). It didn't take long to get it out and get the connector cleaned & in good shape.

I still had a problem with the partially broken male pin on the sensor. As I cleaned up the connector on the sensor, that pin crumbled and I was left with nothing to connect to.

I left the cover off the sensor untill the end of the proccess. (After I had everything finished and connected under the car, I put the cover on as a last step before bolting the sensor and associated parts back into place on the car).

I took a small drill and drilled a hole from the outside the sensor by the connector to the inside of the sensor next to the pad on the same side. I used the drill and some care to create a small cavity where the connector had been so the wire could go stright into the female connector on the harness.

Then I put a small insulated wire into the hole and solered it to the pad associated with the pin. I left enough wire to push into the female connector by hand (about 1.5 inches) and enough inside the wensor to get hold of with a small plyers.


At this point, I checked the wiring with a multimeter.

I made a small loop on the wire protruding out of the sensor. I also made slight lipon the loop to help it catch inside the connector. This would offer some resistance so it would not be pulled out as I worked the connector onto the sensor connector. I was then able to push it into the female connector and get it to stay with a fair amount of light tugging. (important for the next steep).

With the wire into the connector I was able to pull the wire inside the connector while pushing the connector into the sensor. With some care, I got the connector into the sensor with the wire sill into the connector. (it took 2 tries - being sure not to pull hard enough that the wire slipped out of the connector or not hard enough that the wire did not bunch up and block the connector from seating properly.

I turned the care on and Voila. No more problem. I adjusted the headlights.

I put the cover back on and sealed everything to prevent future problems.

I had tried to find a replacement new or used. Even the used sensors I saw on e-bay were going for $250 or so. It is not like years past (am I dating myself??!) when you called a junk yard, they said yes they had a car in row 6 on the left ... go down and take it out for maybe $5 or 10 or more if it was really and expensive part). Today, the want a lot for items they know are costly to replace now or rebuilt). Maybe I just didn't have the patience or could not justify paying anything for such an obvious design flaw.

Now I have time to look for a cheap replacement, new or used. Or to just ignore, adjusting the headlights if I put a load in the vehicle.

Hope this helps, Paul

 

It would be more convenient, long term, to put a ~2K potentiometer right at the head light leveling ECU (wiper goes to SHR), which is on the passenger side under the dash. Cut the wires from the H12 connector, and solder on the control. This will allow for the adjustment of the lights when it comes time to carry a load.

 

Yes. My big concern is that if the Toyota service department seeing it and having a fit! They seem to go into panic mode if something is out of their comfort level, like asking them to set or leave the tires inflated at 42 lbs cold and not reduce pressure if they are warm.

Regardless, an excellent idea nh70. and Would certainly be easier to implement as well as for level adjustments!

 

I have the simplest solution which doesn't require any money.

The component your looking for is the 04 05 06 Toyota Prius Headlight Leveling Control Module 89960-47020 (Headlight beam level control in the third image), which is a black box located in the passenger side dashboard in the 2005 prius (it should be in the same location for 2004). If your headlights are in the proper position, all that needs to be done is to remove the connector from the Module.

Start by removing the lower glove box and the rightmost vent panel(must have the upper glove box open to remove the pannel). Using a light and looking directly into the area once occupied by the vent panel, you should be able to see the black box recessed to the right back. You won't be able to read the sticker that says Headlamp Leveling you'll have a view similar to the second picture but with the unit being plugged in. however there isn't a ECU the same size that is black on that side. make sure your car is off when you unplug the unit.

You should no longer receive the headlight leveling warning, no need to look at the undercarriage to find the sensor.

You should also check your cabin air filter while the glove compartment is off, mine was filthy.


Hope this helps, -S

 

250 used on eBay? Man I gotta start farming these things at the pull it yourself yards. Nothing corrodes around here. Cars still have their original exhausts after 250,000 miles

 

Great solution. Edited with a few extra tips.

 

Thank you.............. that's was the easiest fix for that "feature"... !

 

Thank you! Just bought a 2005 prius and finding numerous issues (this is today's little slice of hell) so I greatly appreciate your instructions

 

There is a difficulty in that Toyota was only allowed to use the extra-bright HID headlights on condition that they add a sensor to keep them from pointing up into the cabins of passing cars.

If you don't want to buy the part, consider mounting a rheostat on the dash and connecting it to the wires that lead to the sensor. The sensor is just a rheostat anyway. If it's mounted on the dash it will no longer be automatic, but you will be able to adjust it by hand, allowing you to not blind passing motorists.

If this is still too much, consider just pointing them all the way down and leaving them there. This way you won't have the expensive sensor, but you will still be a decent guy.

 

Chiming in to say a HUGE thanks for this tip. I just bought this Prius, and it didn't even have the sensor mounted on the car. Unplugging the ECU fixed the "red triangle" and yellow headlight on the MFD. Thanks again