I tried looking for the 2 green and 2 black plugs under the dash board to tie them together and erase the codes (my code reader won't) but I only have 2 green plugs, is this normal?

 

You should have two green plugs under your dash - in the vicinity of the driver's left knee. They are male and female - they connect to each other (and serve no other purpose). When connected, the vehicle is in 'diagnostic mode'. You might use this mode to, say, reprogram the ECU. Merely connecting the two green connectors doesn't do anything - you also have to turn on the vehicle's ignition switch. When you do this, all sorts of things will happen: lights will flash, relays will cycle, fans will start and stop, etc. It's interesting to watch.

As to your first post, for many scan tools, you connect the tool (it will light up, since the OBD-II connector is always 'hot') but you will need to turn on the ignition before you can read or clear codes.

The alternative method of clearing codes is disconnecting the battery for, say, 30 minutes. The codes should clear, but your engine will need to re-learn the idle (and this may occur clearing codes with a scan tool as well). And, you will have to re-program your radio.

Even if you clear a code, it may immediately return if the underlying condition is still present. As a simple example, you might get a P0442 'evaporative leak' code because the gas cap was not replaced. If you clear the code but don't replace the gas cap, the code will come back, sometimes with amazing speed ;-)

 

clearing the codes with a scan-tool also resets all the parameters and idle etc needs to be re-calibrated. (the ecu will do this on its own over time)

It's very much possible that the error condition continues to exist. So when you clear the codes, and start the car, the codes come right back.

 

Thanks for the replies! The car hasn't misfired for weeks now, any thoughts on why the misfire codes won't leave?

 

They won't leave because whatever is causing them is still present. Here are some ideas from this site:

Run the tank dry, fill up with Chevron premium and continue to do so for a week, see if it comes back.

Seafoaming the engine gets rid of surface crud. Running a couple of tanks of premium with a good add pack cleans a bit deeper

Test the coils as cylinders 3 & 4 are "companion" cylinders and the engine has a "waste spark" ignition system (pair of companion cylinders are fired at same time). The secondary coil (where the plugs wires are) posts (the pair across the bottom, and the pair across the top of the coil assembly) should be around 11.2Kohms (+/- 15%).

Examine the coil pack for tracking, small cracks, etc. If any doubt, replace the coil pack. Ditto for the sparkplug wires. NGK makes a great replacement set. I don't recall the mileage on your vehicle but for a 2003 vehicle, you've received your money's worth from both components.

You said you cleaned your MAP. You might clean it again. Or, consider replacing it.

I read that also oil sometimes leaks passed the tube gaskets onto the spark-plug and causes a voltage drop. . .

Pull your plugs and check them. Also, be sure you are using the correct spark plugs. The NGK double-platinum series of plugs are specifically designed for your wasted spark ignition system.

To me, it sounds like a vacuum leak somewhere, like a vacuum line blew off the manifold. This is very common on the Legacy's with the plastic injection molded intake manifold since they did not barb the ends of the connectors or put clamps on them. It could also be two bad injectors, which happened to me on my outback and got the same result.

For your age vehicle, all the vacuum hoses (which are non-reinforced rubber) need replacing. Replace them with reinforced fuel line or reinforced PCV hose - standard auto parts store fare. The only exception is the brake booster hose - it's got a check valve in line, so use the OEM part.

I could go on and on, but better you do the digging. In Google, type "P0303 P0304 site:subaruforester.org" [without the quotes] and visit the numerous folks who have been there / done that.

FWIW, two cylinders on one bank immediately suggests "ignition issues".

 

Tonight I pulled the air box/intake off and re-cleaned the butterfly and all other ports on the intake (turns out I missed a bunch of build up). Re-attached everything and started car with code reader. Now it's showing P0032, this randomly showed up in the past 5 hours since I got home from work. The car ran great the whole ride home. Should I start checking wiring at this point? I don't think it's a head, it doesn't lose coolant or oil, no bubbling coolant or milky looking oil. No drips or overheating. Any thoughts?

 

P0032 is a front O2 sensor issue. Remove the front sensor, check the wiring, inspect the sensor, clean it up so it will make good electrical contact and re-install. Or, you could just replace it. Replace with a genuine OEM or Denso part - <$100 on eBay. Don't use an aftermarket O2 sensor in front.

The front O2 sensor is absolutely critical in running the engine. There is no replacement interval for this part, but they don't last forever, and they have to live in a really rough neighborhood. Given the critical nature of the part and the other issues you have been having, a new front O2 sensor might be a good investment.

Yes, keep checking the wiring. Look for vacuum leaks, etc. The devil is in the details and sometimes the smallest detail can cause major problems.

The best DIY test on coolant is watching the level in the overflow bottle. If it goes up and down and you're not using coolant, you should be good to go.

 

Also, checked the coil and wires. No shorts, no arcing. Replaced all wires/plugs coil within a year. No oil in boots, and no corrosion on either end.

 

Is it possible that a bad AF sensor is causing the other sensors to throw codes? I replaced the rear 02 sensor and tried resetting the codes and nothing cleared. (Tried resetting with a OBD2 scanner and by pulling the battery)

 

Yes that's possible, particularly the front O2 sensor. Between the MAF and front O2 sensor, that's what makes your engine run (fuel wise).

The rear O2 sensor doesn't do so much - maybe next to nothing depending on who you believe. At the very least, the rear O2 sensor make your vehicle OBD-II compliant. It also generates significant parts and service sales for Subaru by telling the owner that his catalytic converter is below efficiency.

If you have an OBD-II scanner / eraser, there's no reason to be disconnecting the battery. Just be sure you're using the scanner correctly. Some are rather cryptic in how they work, position of the ignition switch, etc.

 

Installed a new AF sensor tonight and now the car barely runs, and misses (P0303-P0304) It hasn't missed in weeks! Now even if I put the old (bad) sensor back in it still misses. Right after putting the brand new sensor in hooked up the OBD2 tool to erase the codes and it wouldn't, does this seem weird? The (2 week old) Catalytic converter I put in was realllllly hot after running the car for just a minute or two, probably a terrible idea to start the car but I thought it might not pick the sensor up unless it's ran. Any ideas? Clogged muffler or something? I'm at my wits end with my Subie! These are the codes its showing:
P0303, P0304, P0107, P0032, P0037 PENDING P0303, P0304, P0107, P0032, P0129.

 

Clean the battery terminals, reinstall the leads. Follow the ground wire to the frame and the engine. Remove each ground connection, clean the area and re-install. You have an engine electrical problem, most likely on the ground side of the circuit.

 

Now to top it off, it popped codes P0748 and P0778. I'm starting to think this car hates me.

 

Scratch that last one, I bumped the connector loose. Re-plugged and we're golden. I feel like I accomplished something because I cleared codes that I was dumb enough to cause.

 

Scratch that last one, I bumped the connector loose. Re-plugged and we're golden. I feel like I accomplished something because I cleared codes that I was dumb enough to cause.

Finally, a glimmer of hope.

In addition to checking grounding points, start going through the electrical connectors under the hood. Pull them apart, inspect, re-connect. Actually, you might do that several times for each connector, since the act of separating and re-connecting scrapes crud off the contacts.

Your Subie doesn't hate you. It's like a dog, who constantly demands "prove that you love me".

 

Thanks for all the replies Dave! If I ever make my way to North Bend I will owe you a beer or 6. Ripped all of the grounding points off in the engine compartment and cleaned them, they were super dirty. Also pulled the bracket off with the Main harnesses for the motor, it has the AF sensor connector attached. Seems like it never seated well in there so I cleaned it up and plugged the new sensor back in. (Seems to fit WAY better not attached to that bracket) Now it clears the PENDING P0032 and P0037, but not the current codes. Also, the tranny codes that I made happen won't clear, will those clear after a few driving cycles?

 

There's definitely light at the end of the tunnel ;-)

If your grounding points were that dirty, you need to start a very systematic check of every electrical connection on the vehicle. After you pull one apart, check it, and then re-connect, you might mark it in some way. There are a BUNCH of connections on your car - modern cars use electricity for just about everything.

Some users say that some codes will clear themselves. An example is P0442, when someone leaves their gas cap off. Personally, I clear them with the scanner and don't wait around for something that may not happen.

Do you know the history of your vehicle? Are you the only owner? Any chance it did some deep water fording for a previous owner? A delayed symptom from water ingress is that strange and unexpected things start corroding. This is not a reason to panic - but it does mean you will have to be diligent in attacking the corrosion problem - more so than an owner of another vehicle. If you notice many corroded connectors, you might also add an aerosol can of contact cleaner to your arsenal.

I cleaned the ground points on my 06XT (137K) - I do stuff like that - but they really weren't that dirty. It did give me a warm feeling.

 

It's from Colorado, then went to Illinois where a high school girl drove it. I know this cause of all the glitter covering everything in the car. I had the car fax when I bought it, and it had a perfect maintanence history, no accidents, and only 82k when I bought it 2 years ago. Had to redo the head gaskets/timing belt/water pump within a month. I'm guessing the car sat or was only driven on very short trips from the first 2 owners. I will start ripping apart (and reconnecting ) the harnesses and connectors tonight and post back if codes start clearing. Thanks again for your input!

 

AWESOME NEWS! I pulled the passenger side carpet out tonight and got to the ECU. Pulled all plugs out and wiggled wires into them as best I could. Pulled out the ground that connects to the floor beneath the ECU, sanded all the paint from where it terminates and cleaned the area up. Reconnected it and hooked the ECU back up. Checked codes afterwords and lost ALL CODES except the P0107 and P0129! I ran out of time but I will troubleshoot the MAP sensor tomorrow and post again on that. I'm an electrician and wonder how on earth anyone could connect a ground onto a painted surface. If you're reading this and have a bunch of sensor/engine problems or codes that you can't reset, I suggest pulling the ground by the ECU and cleaning it up!

 

So I finally got to trouble shoot the P0107 and P0129 codes, and threw a new MAP sensor in which cleared the P0107 code. I still cannot get the P0129 to disappear. It think I have all the correct voltages at the MAP Sensor itself (5.1v on Pin 3, 2v on Pin 2, and pin 1 is 2ohms to the block, does this look correct?) I'm having trouble finding a wiring diagram to check things at my ECU though, seems like every page I find shows different connectors for the ECU. The only thing I can think is to check at the ECU to see if I'm getting the 2v signal from the MAP, is this correct? Or is it safe to assume, like the repair manual says, that if I have a P0129 code and no other codes that I need to replace the ECU?

 

Bought an ECU from a scrapyard. Still have a P0129 code. Has anybody who is reading this had an ECU go bad? If so, what were the symptoms and did replacing the ECU fix them? Out of ideas...

 

Had a mechanic buddy come by with his Snap-on scanner that can track and do all the fancy stuff, and we finally got to the bottom of it. Turns out the MAP sensor I bought was a generic chinese knock-off (guy on eBay claimed it to be OEM) and all it did was clear the P0107 code, and it sounds like that was all it is designed to do. It wouldn't interact with the ECM properly, so the car ran like garbage if it ran at all. It also wouldn't clear the P0129 code. Bought the Subaru genuine replacement (P/NO 22627AA220) and all codes cleared. The moral of all the headache I've gone through in the past month is don't buy anything other than the exact brand/PN that Subaru recommends, and clean all of your grounds on the entire front end of your vehicle if you are experiencing electric issues.