Forester Air Filter Assembly Trouble

subaru
forester

#1

My girlfriend just recently bought a used 2001 Forester with manual transmission. It’s in decent shape, except the former owner, for reasons known only to God, replaced the OEM air filter with a cold air intake.

Anyway, the damn thing is throwing problem codes all over the place and he had the OEM air filter assembly, so I was going to put it back on. As it turns, out, he had none of the fasteners, so I went on a scavenger hunt online finding the part numbers for all the bolts/fasteners. I think I’ve found them all.

One problem. I have two parts that don’t show up on the Haynes Guide or the Subaru parts diagram. I think they’re brackets of some kind, but otherwise I’m drawing a blank. I don’t even know for certain that they’re related to the air filter assembly. Can anyone identify these two parts?


#2

Those are tie down brackets used for shipping, they were under the vehicle, one front and one in the back.


#3

Yes. Tie down shipping brackets which so many think are for towing.


#4

In other words, I don’t need them, correct?


#5

What are the codes?


#6

@cdaquila can we get this cleaned up? It looks like a preloaded “signature” from email…


#7

Sorry. I replied on email and it did this.


#8

Cooling Fan Malfunction Rationality Check.

Knock Sensor 1 Circuit High Input (Bank 1).

Cat System Bank 1 Below Threshold.


#9

Thanks. Just so long as I’m not missing parts.


#10

None but the last has any relation to the cold air intake and I doubt the last (I am assuming the code is a P0420) does either. Posting the actual trouble code helps us the most. to diagnose things as descriptions vary somewhat.

This Subie need some work. Likely a fan relay, a knock sensor or the wiring for the knock sensor and a catalytic convertor may need to be replaced. If you only have one cat, and 3 O2 sensors, that may mean the forward O2 sensor on bank 1 needs replacing.


#11

Codes are P0483, P0328 and I didn’t get the third.

I figured I had at least one sensor problem. I wanted to get the original air filter assembly back in to see how many of the codes were legitimate and how many were just because the Forester hated the cold air intake. The guy she bought it from said it started throwing the codes right after he installed it.


#12

Ok, P0328 MAY go away after replacing the CAI. It can get thrown with a lean fuel condition which a CAI may cause. You might get lucky there.

Since the P0483 code is a fan electrical issue, look near the CAI and stock air cleaner brackets for wires leading to the cooling fan that are pinched or broken. Maybe even disconnected. One may have been damaged by a ham-fisted CAI install. Check the fan relay as well.

Swap the CAI, clear the codes and see what comes back. Your local auto parts store may read and reset the codes for you for free,


#13

Good idea to replace the custom CAI with the original. Some of those codes may well go away. Little concerned about the engine cooling fan tho. That wouldn’t likely be affected by the air intake mods, and you may be at risk for engine overheating. Another possibility is the fan is working ok but the engine coolant temp sensor isn’t, and that confuses the engine computer. Suggest to idle the engine from a cold start in the driveway. Monitor the dash coolant temp gauge carefully. The gauge should start to go up, and around the midway point on the gauge the radiator cooling fan should turn on automatically. Does it?