Spring latch for low beam bulb will not secure and bulb does not seat fully.

There should be separate fuses for high and low beams on a Prius. If one of your headlight bulbs is bad, it could have blown the low-beam fuse. Check for blown fuses behind driver's side headlight fuse panel. If new one blows, replace headlight bulbs and try again.

On 2004-2009 Prius, driver's side headlamp bulb can be replaced by removing hold down screws and folding fuse panel upward to access rear of headlight assembly. Large round cover with 3 tabs unscrews about 1/4 turn to remove. It's really tight and held by friction of large O-ring so it'll take some muscle but it will eventually give. Be careful replacing bulbs as metal clips can be easily installed incorrectly resulting in tilted headlight beam. 3-tabs must rest on flat surfaces on mounting area before spring clip can be latched in place. 3-prong plug can be wiggles sideways/up and down to remove from bulb.

I would check for voltage at the dimmer switch first.

Here's what I did to change the driver's side halogen low beam bulb #9006. Do so at your own risk.


1. First ensure fuses are OK. There are four(4) 15A fuses in the fuse box under the hood - drivers side. All are clearly mapped out on underside of fuse box cover. I used the continuity tester circuit on a VOM to ensure they were OK.

2. Remove large plastic shroud that runs across from one side of the top front under the hood of vehicle to the other side. 5 plastic pins held mine in place. Once off -- you'll be able to see your vehicles radiator cap. Removing this helps provide some additional access and leverage to better work with.

3. Remove battery negative cable - 10mm socket

4. Remove battery hold down bracket - rod - one(1) 10mm bolt at front - one(1) 10mm nut on rod. Deep socket 10mm helps with the 10mm nut.

5. Remove battery positive cable - 10mm socket

6. Remove battery and plastic battery tray

7. You should see the halogen low beam bulb #9006 in front of the fuse box(drivers side). Mine has a brown electrical plug connected to it. It helps to first remove and place out of the way - the parking light which is just to the left - the assembly for mine is light gray in color. Doing so gets that wire out of the way. One less distraction when you reach in to remove the low beam halogen bulb #9006.

8. Remove electrical connection from halogen low beam bulb #9006. There's a locking tab on the bottom - press in and while doing that - push down on the electrical connector from the top. It comes off without a great deal of effort.

9. Remove halogen low beam bulb #9006 by turning counter-clockwise - looking at the bulb from the back. Mine did not want to twist loose right away. Go slowly - take your time. It should eventually come loose. #9006 bulb came out easily even with the fuse box nearby.

10. Install new halogen low beam bulb #9006. I opted for a $10 Wal-Mart Sylvania #9006.

11. Reconnect electrical connection to the new halogen low beam bulb #9006.

12. Clean battery tray and terminals on battery + connections on battery cables.

13. Install battery tray and battery

14. Connect positive battery cable to battery - 10mm

15. Connect hold-down and rod + one(1) 10mm bolt at front and one(1) 10mm nut that goes on rod at rear.

16. Connect negative battery terminal - BUT - before doing so - have your remote locking/unlocking device handy. As soon as you connect the negative battery cable to the batteries negative terminal - the horn will sound(alarm). Quickly depress the UNLOCK button on your vehicles remote. Finish tightening the negative cable. You should also see that the low beam is once again functional as it will come on when the alarm is sounded.

17. Reinstall large plastic shroud and all lock down tabs

18. Start car and set clock/radio settings/etc.

19. There is a procedure to resync the power windows. The following provided by inov8 from another forum.

Copied from TSB PD002-05

NOTE:
Anytime the battery terminal has been disconnected, please initialize the driver's door
power window and front passenger's door power window after reconnecting the
battery terminal.

With ignition switch in the "ON" position, do the following:

1. Push down and hold the driver's door power window switch to completely open
the window.
2. Pull and hold up the driver's door power window switch until the window closes.
Continue holding the switch for approximately one second until the switch changes
from blinking to a constant illumination.
3. Check for proper operation of the "one-touch open and close" function by fully
pushing the switch briefly to the "DOWN" and "UP" positions.

At this time the power window switch for the passenger's door window should
be blinking.
4. Push down and hold the passenger's door power window switch to completely open
the window.
5. Pull and hold up the passenger's door power window switch until the window closes.
Continue holding the switch for approximately one second until the switch changes
from blinking to a constant illumination.
6. Check for proper operation of the "one-touch open and close" function by fully
pushing the switch briefly to the "DOWN" and "UP" positions.

Sunroof initialization is similar.

20. There is a procedure to resync power seats. Extracted from factory service doc:

Using seat switches - fully slide seat fwd. - fully recline seatback fwd. - fully raise seat cushion and head rest.

Using seat switches - fully slide the seat rearward - fully recline the seatback rearward - fully lower seat cushion and head rest.

1. Remove the three pin-type retainers, two screws and the radiator defector.
2. Remove the 4 bolts securing the headlamp assembly and remove headlamp assembly.
- Disconnect electrical connector
3. Remove the 3 hex-head bolts and 2 torx-head screws and remove headlamp protective cover.
4. *****Standard low-beam bulb*****
Disconnect the connector from the bulb and remove the low beam bulb.
5. *****HID low beam bulb*****
Release the spring tabs and remove the HID low beam bulb
Disconnect the connector from the bulb
6. *****High beam bulb*****
Disconnect the electrical connector and remove the high beam bulb.
Reverse order to install

.
.

Low beams are easiest to reach. Open the hood, find the locking cap behind the light housing and turn it a half turn to remove. Unplug the bulb. Disengage the spring lock holding the bulb in place and remove the bulb (be sure you don't touch the glass).

The bulb base has three small flanges that seat right into corresponding slots in the bulb housing. Seat the new bulb using these flanges, lock the bulb into place with the spring lock and replace the locking cap.

The high beams are harder to get to. You might need to pull the battery on the driver's side. The windshield washer tank on the passenger side might also give you some problems. Once you have room to maneuver, the procedure for changing the bulbs is exactly the same as for the low beams (they even use the same bulbs: H7).

Release the locking ring, then withdraw the halogen bulb from the headlamp assembly


Removal & Installation

This procedure only applies to replaceable halogen headlight bulbs (such as nos. 9004 and 9005); it does not pertain to sealed beam units.

1. Open the vehicle hood and secure it in an upright position.
   
2. Unfasten the locking ring which secures the bulb and socket assembly, then withdraw the assembly rearward.
   
3. If necessary, gently pry the socket's retaining clip over the projection on the bulb (use care not to break the clip.) Separate the bulb from its socket.
   

To install:

1. Before installing a light bulb into the socket, ensure that all electrical contact surfaces are free of corrosion and dirt.
   
2. Line up the replacement headlight bulb with the socket. Firmly push the bulb into the socket until the bulb is seated. If so equipped, make sure the spring clip latches over the bulb's projection.
   

WARNING Do not touch the glass bulb with your fingers. Oil from your fingers can severely shorten the life of the bulb. If necessary, wipe off any dirt or oil from the bulb with rubbing alcohol before completing installation.

1. To ensure that the replacement bulb functions properly, activate the applicable switch to illuminate the bulb which was just replaced. (If this is a combination low and high beam bulb, be sure to check both intensities.) If the replacement light bulb does not illuminate, either it too is faulty or there is a problem in the bulb circuit or switch. Correct if necessary.
   
2. Position the headlight bulb assembly and secure it with the locking ring.
   
3. Close the vehicle hood.
   

Just above the headlight assembly are two angled tabs, pull these straight up (they may need some effort). These will release the assembly, carefully pull the entire assembly forward. Access to the headlight bulb is behind the two rubber caps, the upper cap is for the low beam. Remove this cap, twist the headlight bulb socket CCW and remove. Disconnect bulb from harness by prying up gently on locking tab on socket, and pull bulb out. Being careful not to touch the new bulb glass surface with your finger, plug it into the socket and install it back into the headlight assembly turning it CW. Reinstall rubber cap, seat headlight assembly on frame, lining up the bottom and top pegs. Once the assembly is fully seated, push the two angled tabs down, locking the assembly in place.

On the back side of the headlamp assembly, there is a cap (screws on and off). remove this cap and there is a connector (2 pin) connected to the bulb - remove it. Then there's a spring retainer holding the bulb in place -- remove it from its latch and you can remove the bulb. Install new bulb and reinstall the retainer and connector and cap.

Left front low or high beam headlight: remove battery, remove weather cap, pop-off 2-prong connector, depress spring holding bulb in position, use inspection mirror if necessary, one end of spring is caught beneath a lip, Move spring past lip and lift up, it will rotate upward and is fastened on opposite side. Remove old bulb, install new 55 watt halogen bulb (H7-55) available at Walmart. Install new bulb with tang in slot at bottom, fold over spring and depress to hook end under latch point, install 2-prong electrical connector, install weather cap, turn about 1/8 turn to lock into position. Reinstall battery, clean terminals and cable ends, place new no-corrode rings (available from Walmart) around battery posts, install cable ends, and tighten.

Right front headlights: not necessary to remove battery, otherwise same essential procedure.

Note: Lower and upper beams all use same H7-55 bulb.

Disconnect the connector.

1. Remove the socket cover. CAUTION: Do not touch the surface of the bulb with hands or dirty gloves as the bulb may pop after a short time. If the surface does become dirty, clean it with alcohol or thinner, and let it dry thoroughly before installing.
2. Release the bulb securing spring, and remove the bulb.
3. Replace the bulb, and connect the connector securely

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