How many oxygen sensors does a 2003 Honda Odyssey have?

SOURCE: 2003 Honda Oddyssey - PO325 Knock Sensor

If The engine in your van is a 3.5L, the knock sensor is under the upper intake manifold. This has to be removed in order to access the sensor on top of the engine block. The job requires an upper intake gasket set and about 1.5 hours to do; if you are handy with tools. For those who aren't; better off leaving this one to the professionals.

SOURCE: changing oxygen sensor for a 2000 honda civic lx

both are located in the exhaust system. You have to get the car off the ground and follw pipes. You cant miss the O2 sensors.

SOURCE: 2003 Honda Odyssey Brake light replacement

open the rear hatch. Between the tail light housing and the rear hatch opening there is a trim strip with two flush fitted flap doors. Insert a small straight blade screwdriver into the small slot on the tail light side of the flap. Pry gently inboard and the small flap will open (the hinge side of the flap is on the side of the rear hatch opening.) Now you can remove the screws that hold the tail lamp assembly in place. Finally, there is still a "spear point" clip that fits into a socket near the front outboard corner of the assembly. Gently pry with a tape wrapped screwdriver (avoids scratches) and force the assembly straight back. The clip should release and free the assembly so you can change the bulb(s).

SOURCE: 2003 honda odyssey

I assume you mean the front or rear power accessory sockets. You will need to check two fuses. 1) Fuse no. 8 (7.5A) in the drivers under dash fuse/relay box. 2) Fuse no. 9 (15A) in the passenger's kick panel fuse/relay box. Both these fuses must be good for the accessory sockets to have power.

SOURCE: I have a 2003 Honda Odyssey my radio says code

If an audio unit with theft protection is disconnected from electrical power, you must enter a unique code number into the unit or it will not work. This code and the audio unit’s serial number are listed on the anti-theft ID card that comes with the vehicle. If this card is lost, you must obtain the audio unit serial number in order to get the radio code. Some newer vehicles allow you to retrieve the audio unit serial number electronically from the radio. Refer to your owner’s manual for the specific procedure (the following usually will work: Turn the radio off. Push the preset 1, preset 6, and power buttons at the same time, then quickly release.)
. Some older vehicles (model year 2003 and older) require a visit to the dealer in order to retrieve the audio unit serial number. Once you have the audio unit serial number, you can call Auto Customer Service at (800) 999-1009 or have the dealer look up the radio code.
Hope this gets you started on getting it playing.