Subaru How-Tos

2005 Subaru Forester XT Premium Front O2 sensor R and R (randr removal and replacement)

My check engine light started coming on, a P0031 "HO2S Heater Control Circuit Low Bank 1 Sensor 1"

Some internet research says this is the pre-cat, pre-turbo sensor. It lives in the collector where the two banks of cylinders join together.

Both front and rear sensors live on the passenger side of the car. The front sensor lives in the front of the passenger side wheelwell.

Sensor was ~100 bucks from multiple sources. Some places indicate is wide-band. The sensor I ended up with is the "Denso Air/Fuel Sensor p/n 234-9120"

- First, double check that the sensor you got has the right plug. It is here

and should look like this.

- Lift and support front pass corner of Car (safely)

- Remove wheel

- Remove cover panel

-- two screw-center, one pop-center

- Unclip Wire connector

- Remove wire from retainer at top of engine compartment

- Next need to remove sensor wire clips near sensor. Easiest way i found to do this _right_ was to remove the airbox.

-- Removing airbox--

-- Remove MAF electrical plug

-- Remove cooling hoses from clips on top of air filter housing


-- loosen hose from air filter housing to turbo inlet pipe

-- unclip air filter clips (2)

-- remove 2 bolts holding in bottom of air filter housing (12mm on my car)

- Remove wire retainers next to sensor

-- squeeze clip on back, new O2 sensor came with new set. I found a pen barrel worked perfectly! :)

- Fish wire down into wheelwell by sensor, to unscrew without twisting up wire

- Unscrew sensor using wrench or sensor tool (7/8 / 22mm)

- Compare old and new sensors, wire lengths and plugs

- Torque new sensor to proper spec (22.1 ft lbs according to this thread)

- Installation reverse of removal

- Torque wheel lugs to 72 ft lbs (as per owner's manual)

2005 Subaru Forester XT Premium Fuel Injector R and R (randr removal and replacement)

I recently ran into problems with a missfire on my Forester. In attempting to find the problem, I've done all sorts of injector swapping about.

This car has the side-feed fuel injectors. I gather that, generally speaking, they are much easier to swap than the top-feed variety.

Three of the injectors are pretty easy to swap; cylinders 1,3, and 4. Cylinder 2 however (rear passenger side) is a pain in the ass. You have to remove the coolant reservoir, and sqeeze past a mounting bracket that supports the power steering lines.

I suggest purchasing a 4" T25 torx driver (screwdriver style) such as the one pictured below, as it will make removal of cylinder #2 injector _much_ easier.

Easy side first; cylinders 3 and 4

For clearance (not needed) remove windshield wiper reservoir

Remove wiring support bracket -- be aware of ground wire under front bracket mount

Remove injector wiring #3

Remove injector wiring #4

Remove injector hold down clamps (torx t-25 in my case)

use flathead screwdriver to push under outer lip of injector and pop out.

For hard side (cylinders 1 and 2)

remove intake tube from airbox to turbo inlet pipe. (best to unclip the airbox top to keep from breaking the turbo inlet pipe with leverage)

remove coolant expansion tank. THe tow three hoses should not really leak, but the bottom one will.. plug it up and tuck it up to keep from losing your coolant!

remove injector wiring #1

remove injector wiring #2

remove injector hold down clamps (this is where 4" t25 comes in really handy, squeezing through hole in power steering line support bracket)

On reassembly, I used this brake slider lube on the o rings.. The first couple of times i didn't use enough and it was tough, but with a good mid-thickness coating of this the injectors pop right in.

Fuel Injection Pressure Test Port - Fabrication (quick connect)

lines measure 7.91mm/.311" o/d -- very near 5/16" which is 3125"

So we want to assemble a hose like this:

male quick connect <-> hose <-> tee with shrader <-> hose <-> female quick connect

Here are the parts I used:

5/16" DORMAN Part # 800120 Steel Body Fuel Line Connector; 5/16 Steel Fuel Line Repair -- female quick connect to hose barb -

5/16" DORMAN Part # 800154 {#E3FZ9291E} Steel Fuel Line Repair; 5/16" x 12" Double Bead Line -- double bead 12" straight

5/16" DORMAN Part # 800229 Fuel Sending Unit Repair Line; 5/16" x 4" Double Bead Line, 90 Degree End -- double bead right angle 4" no hose bead

GATES Part # 27335 {#27091, H344, H344A} Fuel Injection/MPI Hose - 5/16" x 2' (180 psi) -- fuel hose 2 ft

This part was wrong - need to find a different schrader valve


rock auto had them all for under 40 bucks shipped, except the 5/8 tee with 1/8 NPT threading. Had to get that elsewhere..

I only found one i think; the B&B "Fuel Pressure Gauge Fitting" #10400. Jegs, stefs, and LC engineering.

Or, using the 'Mallory part # 3155" along wiht a couple mnpt 3/8 to 5/16 hose barb