My daughter took her '04 manual tranny in for CEL and for $99 dealer diagnosed "Code P0037 Bank 1, O2 Sensor heater circuit. " Recommend replacing O2 sensor at about $275. Is this the higher cost $251 front sensor or lower cost $121 rear sensor, using Mazda parts online.
Forum threads claim front sensor is a pain in the butt to change next to oil filter, so for the $25 shouldn' t I have dealer install it? Are pictures available of area where both sensors are installed

 

our 02 sensor isn't near the oil filter.
the front is at the exhaust manifold and the rear is by the catalytic converter.
you'll need the car up on jack stands, the front passenger wheel off to do the front sensor, the rear sensor is just hanging there so once it's raised it's easy to get to.

 

plus a sensor socket. without one your going to have issues, especially if its been on there a while

 

replacing the sensor are very easy just do as jedi said, and it does need a special tool socket like wingle best recomended.

tool

http://cgi.ebay.com/O2-SENSOR-FLEX-H...item1c181d9061

here is a pic of the exhaust manifold, you can see the hole where the oxygen is located, you need to remove your passenger wheel to get to it.

and here is a pic of the other one located in the catalytic converter

http://www.google.com/imgres?imgurl=...26tbs%3Disch:1

 

Sorry to bump old thread but I just replace my front and rear o2 sensors on my right hand drive rx-8 in oz.

I found that the special oxygen sensor socket/tool wasn't required.

Just a wrench with one bent end (to access front o2 sensor)

The reason why the special tool isnt required is because the electrical connecter can actual fit through a 22mm close end wrench

My tips on o2 Oxygen sensor replacement

WD-40 the old sensors helps removal
22mm wrench, you will need to use one with a bent end to access the front o2 sensor
Undo the electrical connection and feed through wrench to access the sensor
The electrical connection for the front o2 sensor is in a tight space, find someone with small hands/arms - removing the oil dipstick also helps with space
A small hammer may be required to gently nudge the wrench to unscrew the old sensors initially.
Rear sensor is very easy to replace
More time required for the front sensor
There is a metal attachment to the front section of the exhaust to the gearbox, you can remove to give better leverage if required for access to the front o2 sensor



Reset the ECU via the odometer reset this will clear the CEL light

Cheers