Yep, idle air control code:
P1507 Idle Control System Malfunction (Fail Safe)
Perhaps one of the smarter members can chime in with suggestions.
This code just gutter-balled my '97 Outback – the engine tried to stall shifting into neutral to coast, loped a little, then died. It would only turn over but wouldn't fire. (This was also only days after throwing the Cylinder 1 and 2 and 3 misfires, which I cleared with the OBD and the car ran fine again.) As for P1507, I could have easily just cleared that code too and ran again until she stranded me once more - but I can’t drive around with the OBD plugged in just killing the daily codes. So I pulled out the Idle Air Control Valve (IACV) and cleaned it with carb cleaner - it was very carbon-y. It also has two coolant lines running through it which purged a little coolant when removed - no big deal. I also removed and soaked the PCV valve in mineral spirits and carb-sprayed the MAF sensor and let it dry well since these are parts that can/do come off anyway to get to the IACV. (My mechanic of 10 years said carb spray was fine on the MAF if you let it dry really well - he also loaned me his OBD scanner - thank you 360 Auto Repair, Loveland, CO!) Since everything was now exposed, I did a quadruple by-pass with NGK platinums and OEM wires (thanks to O'Reilly's for OEM!) - hoping this would stop future P0301-P0304 cylinder misfire codes. My owner’s manual just says “NGK” for plugs – not platinums, no Lasers, no dilythium crystals. I tested the Ohms across my coil too - both banks threw the same numbers so I presume the coil to be good (I have the early-year '97 which has the ignitor separately on the firewall and not built into the coil like late 97's, and the wire ports are the females - see my attachment below for testing the early '97 coil.) This whole deal was an all-day job for me (one man) but not very hard with moderate tools. All the plugs were hard to do in against the frame so make sure to have several short extensions (3", 6", etc.) and a couple of swivels for your ratchet. The battery and windshield fluid reservoir did have to come out to replace plugs/wires on the driver side. After reassembly she runs beautifully and No CELs.
Hope this helps some people.
OK, I must be retarded. The car ran fine last night on two test drives - but today it wont start (turns over but won't fire). After reading the threads about Neutral Safety Switch on the manual tranny, I think that's my problem now. Will keep you informed.
Hint: Whomever this guy is, I think he deserves a Scooby snack for the real clue to my mystery here:
1997 subaru legacy outback reset button
While the car would turn over but not start yesterday, that didn't stop her from throwing a P0505 Idle Control something something and P0122 for the TPS. I knew these were faulty codes because I had these sensors unplugged when I tried to start the car once. I plugged in the sensors and cleared codes but the car still wouldn't start. Likewise, I had the air intake off again to route the new Neutral Safety Switch so the MAF sensor was probably tripped out too - but no codes triggered.
I replaced the old Neutral Safety Switch because no matter how shallow or deep I pushed the "button" the ohms test started at zero, threw arbitrary numbers, then ended at zero - I didn't trust the switch or its outputs. The new switch only gave zero at open then arbitrary numbers while depressed. However, with a new NSS the engine still only turned over, no fire. So then I really soaked and cleaned out the IACV again since I had the air intake off routing the NSS anyway. (Watch out! as the IACV is an electromagnetic motor atop a magnetic spindle, and both attract every metal shaving in a 3 block radius so if you pull the motor off the IACV keep them the heck away from everything metallic or the attracted flecks and shavings will eventually grind the IACV out from the inside.) Before removal I scored the IACVs aluminum body with a nail around the screw washers marking the exact elctromagnetic cap position for re-assembly, which worked well. However, the engine still only turned over, no fire.
So I started sweating the fuel pump and relay. I could NOT hear the pump on start up. However, the relay clicked on and off for the 3-second prime time. I pulled the fuel hose off the engine side at the fuel filter under hood and inserted a long hose routing out to a glass jar that I could hold in my hand to see while I turned the ignition key through 'on' and 'start' - no fuel. So I pulled the fuel pump cover off the tank from behind the passenger rear seat and tested the pump's wire harness connection with the key ignition turned on. All combinations of points I tried in the harness plug registered some positive amount of voltage up to 12V. I believed this to mean there was continuity from the relay to the pump assembly. Then I pulled the pump from the tank and dismounted the pump motor itself and stuck 12V on it - it ran quite fine. So I ohm tested the pump's wires just on the pump assembly itself - they registered resistance so I believed this to mean there was continuity to the pump - no wire breaks. So I began searching for the fuel pump relay... then honestly gave up because of the bird's nest of wires under the dash.
But I had wondered about resetting the ECU. Everyone says to disconnect the battery for 2, 3, 30 or 60 minutes to discharge the ECU. Well, I had already disconnected the battery the previous day to install wires and plugs so why didn't this reset the ECU then? Technically, I believe that it did reset something - everything - including the factory installed security system. Previously, when I re-hooked the battery after installing the plugs/wires, the alarm went off, which I was prepared for, and had the beeper ready to silence at first howl of the horn, which I did. Yet, on the dash is a blinking red alarm light which is always on - but was never on during this time that I recall: so as MaGrue says in Despicable Me - "liiiiiight-bhaaaaaalb". So I pressed it and it lit up red again... hmmm. And (thanks to the clue from the link above) under the dash is the dangling little black switch that resets the cars security system - in 30 seconds the alarm chirps thrice and the door locks cycle a couple times – done. So I put the air intake back on the engine, sat back in the drivers seat with the glass jar in hand, turned the ignition to ‘on’, and then to ‘start’. I held up the glass jar and it was half full of fuel.
Somehow the dumb security system must have disabled the fuel pump the first night after I shut her off - or else the whole time performing maintenance the stupid car thought it was being stolen! (I don't recall "beep-locking" the car the first night, I think I just pressed the lock button on the driver door as I exited (as usual). Yet I "beep-UNlock" it every time.) I hooked back up the fuel hose from the filter to the engine, turned the ignition key to start, and the engine fired up instantly! She purrs like a kitten, hauls more butt than before, and hasn't thrown any CELs yet (yes, you're jealous I know, but alas my tomorrow is out there.) As for tonight the car is just trickling on the charger.
I hope this REALLY helps some people.
No causes for concern here folks: the car is still starting and running beautifully after 2 days. (Yep! Just started her to make sure - Murphy's Law - you know.) I wanted to provide you all with closure on this issue. I really believe cleaning the IACV and replacing the NSS were the right things to do - even though it's not conclusive whether it really needed the NSS. However, somewhere in the midst of disconnecting sensors, plugs, and batteries and reconnecting them, then locking and unlocking the car, it must have gone into some kind of Security Lockout and shut off the fuel pump, forcing me into performing that entire fuel system analysis unrelated to code P1507. I am still perplexed as to exactly when and why any Fuel Pump Lockout occurred - I would love an explanation if anyone out there has it. Anyway, good Luck with you and yours. God Bless.
Within one week, the fuel pump started failing and finally immobilized the car. There probably never was any kind of alarm system "fuel pump lockout". However, my alarm manual does discuss a "starter lockout" - which never occurred here. In retrospect, it is highly likely that a coughing or sputtering fuel pump was the cause for the cylinder misfire codes (probably not the IACV P1507 though). A new fuel pump (and incidental new relay) have fixed the fuel system problem for now. Please see that response under "1997 Outback occasionally won't start for a few hours".
Knowing what I know now, I half bet that a bad fuel pump might just be the origin of many similar or indirect problems on all these forums. As far as I know, my pump went 210K miles - but I'm not the car's first owner.