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Hey everyone, I am having some tricky issues with my 93 touring wagon that had a 5spd from an 07 legacy swapped in by a previous owner.

The issue I am experiencing involves what I've determined to be a fuel cut if I open the throttle too aggressively past about 25% when the engine is warmed up. I checked both the stored CEL codes and ran the self diagnosis and pulled codes from that to find a few different things going on.

The stored codes I got with just the black connectors hooked up and the engine off were 22, 45, and 49. The first is a knock sensor code and the other two seem to be MAF related or some other intake related sensor. The knock sensor code could've come from a bad misfire or stalling out when the fuel was cut, I assume, so the other codes are probably where the culprit lies is my guess.

The codes I got while running the self diagnostic setting with the green plugs hooked up seem to tell a similar story. They were code 45 again and, this time, code 51. The reoccurrence of code 45 leads me to think the problem is almost definitely sensor related and code 51 makes sense because the auto to manual swap involved tricking/disabling the neutral safety switch.

So, does anyone have any pointers on where to start looking for this faulty sensor? Or maybe some insight as to what is actually causing this fuel cut issue?

codes = http://legacycentral.org/library/literature/codes.htm
22 = knock sensor / KS
45 = Press. Sensor
49 = MAF

51 = Neutral switch

The KS needs replaced. It's causing your car to go into LIMP mode.

99% of Legacys from '90-'95 will have cracked KS by now (and years ago). Get a new one - supposedly the cheap ones online are OK.

Reset the codes and check again. MANY peeps on here have the same codes related to a bad KS.

Make sure you have the SILVER metal MAF sensor. The black plastic are for NON-turbo / NA. (the '90-'91 manuals NA used the same MAF as the turbos).

Tangent:
'07 Legacy didn't have the mechanical speed sensor, AFAIK. How is your Speedo getting a signal?

I'll pick up a knock sensor tomorrow, it's cheap enough. I do wonder then why I didn't get the knock codes while I was driving it in d-check mode and experiencing the same fuel cut scenario as usual.

If you clear the codes, are the same ones still there? Are you able to clear the codes?

Legacy777 wrote:If you clear the codes, are the same ones still there? Are you able to clear the codes?

Clearing the codes is the same procedure as the d-check mode just with both the black and the green test connectors hooked up, right?

I'll give it a shot when I get home tonight, if so.

D-check is only with the green connectors connected and the clear procedure is with both black and green connected. Sometimes codes won't clear if there is an active code. You can also try pulling the EGI/TCM fuse (No 14) for an hour.

Code 45 - Pressure sensor. that'll do it too.

As far as a replacement knock sensor goes, personally I'd stay away from ones that aren't marked with the factory markings. I installed a Standard Motor Parts one on my wagon a little over a year ago. Recently it went back to the lack of power thing it was doing before. No codes. Pulled the sensor and found it cracked badly, just as bad as the 20 year old one I replaced it with.

You can still get less expensive than dealer supplied ones that are just OE repackaged. I believe they say "JECS" and a bunch of numbers. I just checked rock auto. The SMP one is OE in the picture, but that's not what they're shipping out currently. The Bosch one is probably legit. Even though it is the priciest of the bunch, its still half the cost of a subaru packaged one.

Does the speedometer work?

Have you figured out why the MAF and MAP codes are on?

Generally​ diagnosing codes I always start with the lowest number code and work up. It's very likely the knock sensor is the only problem and causing a multi code fault. It maybe the knock sensor wiring is the culprit causing intermittent readings in check mode.

Thanks everyone for your input!

A few things; firstly I'm picking up a knock sensor in a few minutes and will replace it before I retry running the engine since attempting to reset the codes by disconnecting the battery for more than an hour.

Also, I will clean the maf and try to find this pressure sensor I'm getting the code about, but I haven't seen anything online that seems to be the part it speaks of. Does anyone have a part number or where I can find it in the car so I can look for a replacement?

jamal wrote:Does the speedometer work?

The speedometer does work. I don't know what that means in terms of what transmission it must have in it to give a mechanical speedometer signal, but it does appear to work.

My car did pretty much what you are describing and I found the hose off the boost solenoid if I remember right. It was on the passenger strut tower with oll those other electronic devices. You couldn't give it much throttle at all or it would just die.

subieroo wrote:Thanks everyone for your input!

A few things; firstly I'm picking up a knock sensor in a few minutes and will replace it before I retry running the engine since attempting to reset the codes by disconnecting the battery for more than an hour.

Also, I will clean the maf and try to find this pressure sensor I'm getting the code about, but I haven't seen anything online that seems to be the part it speaks of. Does anyone have a part number or where I can find it in the car so I can look for a replacement?

First replace the knock sensor, then go from there, the code for the pressure sensor is likely because of the knock sensor.
The part # for the map seonsor is : 22012AA020
Part # for pressure exchange solenoid valve : 14774AA341

Well, I replaced the knock sensor with no luck in fixing the problem. I am still getting the fuel cut and a CEL. The harness wiring was cracked and broke while pulling the old sensor. I depinned the old male end of the plug and soldered it to the intact end of the old wiring and sealed it all up with heat shrink. Hooked it all back up and reinstalled everything I had to pull to access the knock sensor, started it up, let it get up to temp and drove it around. I didn't get a CEL until I drove it and experienced the same symptoms as before.

I have yet to check what codes it was throwing and I haven't had any luck in clearing the old codes. I've tried disconnecting the battery as well as pulling the ECU fuse for more than an hour each and was unable to get the old codes to go away. I'll go read the codes its throwing now and report back later tonight. Any input you may have as to how I may have fixed the old wiring wrong or messed anything up in the process of replacing the old sensor would be appreciated!

To reset the ecu the proper way you need to connect both the black and green diagnostic plugs together and drive it 1st through 4th staying out of BOOST and getting up to 35mph.

If your wiring to the knock sensor was messed up I would take a close look at the maf and map sensor wiring as well.

jefferson wrote:My car did pretty much what you are describing and I found the hose off the boost solenoid if I remember right. It was on the passenger strut tower with oll those other electronic devices. You couldn't give it much throttle at all or it would just die.

I just went out to give troubleshooting this issue another shot and noticed a hanging vacuum line, lo and behold it went to the boost solenoid! The car seems to run fine with it attached and immediately started sputtering out after 20% throttle. Thanks for saving the day!

Nice!!!

Glad I could help.

Congrats! I had nearly the same issue, just the vacuum line came off a different location