ThosL Posted November 17, 2015 Share Posted November 17, 2015 I was wondering what triggers the CEL to flash vs. their just going and staying on? I checked the codes and it showed a couple misfire codes, so I will pull the plugs to see how they are and if that is part of the problem. Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted November 17, 2015 Share Posted November 17, 2015 not sure what the ECU's threshold is, but from what I've read, flashing supposedly means active, repeating misfiring is occurring - bad enough that catalytic converters may be damaged. A solid light + recorded misfires, might be a single occurrence, or perhaps a few misfires? but, i have no detailed information aside from that. Quote Link to comment Share on other sites More sharing options...
ThosL Posted November 17, 2015 Author Share Posted November 17, 2015 OK, thanks. Usually I have gotten misfire codes when the wires were compromised. Also got an O2 code. Quote Link to comment Share on other sites More sharing options...
forester2002s Posted November 17, 2015 Share Posted November 17, 2015 A flashing CEL can mean that the system is in diagnostic-mode. There should be 2 green connectors under the steering-wheel. These 2 green connectors should be UNPLUGGED for normal driving. Quote Link to comment Share on other sites More sharing options...
ThosL Posted November 17, 2015 Author Share Posted November 17, 2015 My sister's 1996 Subaru wagon with a 2.2 engine has had that problem of the CEL flashing from time to time; she had Auto Zone check it out and they had the two codes come up; PO302 and PO420. She drives like an old lady which is to say just a few miles a day. She had the plugs and wires changed and a fuel injector and the mechanics have not been able to get to the bottom of the problem. Symptoms are loss of power. At other times without any problems. Quote Link to comment Share on other sites More sharing options...
golucky66 Posted November 17, 2015 Share Posted November 17, 2015 not sure what the ECU's threshold is, but from what I've read, flashing supposedly means active, repeating misfiring is occurring - bad enough that catalytic converters may be damaged. A solid light + recorded misfires, might be a single occurrence, or perhaps a few misfires? but, i have no detailed information aside from that. 1 Lucky Texan is right. for OBD cars that is. And since it's a 96' it has OBD. Therefore, flashing CEL is usually misfire bad enough that the computer sees a significant problem and "usually" should not be driven. As for w/o OBD, forester2002s is right. Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted November 17, 2015 Share Posted November 17, 2015 (edited) p0420 can have a lot of causes, if the car has power-loss or other problems, I'd be tempted to address those first and hope the p0420 resolves after that. Sometimes a p0420 is only an exhaust leak - sometimes it really is a bad cat. conv. Converters are so expensive though - you want to eliminate every other possibility first. 302 is a misfire in cyl 2. many things can cause that, but of course plugs , plig wires would be the first place to look on an older car. Plugs should be NGK, wires should be OEM or Denso. vary from those and risks of problems increase a lot. many people have problems in that system with aftermarket parts. wires can sometimes be moved around. If the problem follws the wire to another cylinder - it's a bad wire. If not, could be a plug or burned valve or ???? Or bad wires/coils sometimes show up if squirted with a plant 'mister' of water at night while idling. any arcing is a failure in the wire or coil. Even looking at the plugs/comparing cylinders can be useful. An infrequently driven car, or car driven short distances can have a lot of carbon build-up in the cylinders. Edited November 17, 2015 by 1 Lucky Texan 1 Quote Link to comment Share on other sites More sharing options...
ThosL Posted November 17, 2015 Author Share Posted November 17, 2015 When I've pulled the plugs on my 99 Outback with a 2.2 I've never noticed fouling. On my sister's car which I just took for a drive, and frankly drives perfectly as far as I could see, the plugs and wires were changed recently. Her CEL flashing problem only happens in the morning and has happened a couple times this week, the days are colder. She is alarmed by any CEL code, I told her it is not a performance indicator. She tends to push the panic button, I will try to reassure her that if she lets the vehicle warm up the in morning for fifteen minutes it will probably not be so much of an issue. Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted November 17, 2015 Share Posted November 17, 2015 if there is moisture in the mornigs, could be a cracked coil i guess. Also, look for oil on the wire boots. maybe leaky valve cover gaskets/oil shorting the high voltage.. (might not be a problem though on 2.2s ?) 1 Quote Link to comment Share on other sites More sharing options...
ThosL Posted November 17, 2015 Author Share Posted November 17, 2015 How reliable are the computer codes? I got an O2 sensor code on my 2.2. Is there an alternative to the $100 replacement part? Quote Link to comment Share on other sites More sharing options...
nipper Posted November 17, 2015 Share Posted November 17, 2015 Flashing = angry. A flashing CEL means something is happening that can cause engine damage. Quote Link to comment Share on other sites More sharing options...
nipper Posted November 17, 2015 Share Posted November 17, 2015 How reliable are the computer codes? I got an O2 sensor code on my 2.2. Is there an alternative to the $100 replacement part? Depends upon the code. Remember if a factory part has lasted X years, odds are the factory replacement will last just as long. Dont go by price alone. Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted November 18, 2015 Share Posted November 18, 2015 Flashing CEL is based on the detection of a condition in which the vehicles emissions exceed 1.5 times the Federal Test Procedure limit for the given engine size. The most common reason for that is a cylinder misfire. A certain number of misfires have to occur within a certain time period to set a code for a misfire on a particular cylinder, and illuminate the CEL. If misfiring continues and exceeds a higher number in the same time period, that will trigger the CEL to start flashing. Codes really only give you a place to start. There is still some diagnosis that must be done to confirm the cause of the code. Misfire codes, for example, can be set for several reasons. No spark, no fuel, no compression, cut it down to the basics. 1 Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted November 18, 2015 Share Posted November 18, 2015 ThosL - even though the codes have definitions, if that definition mentions a specific part - it does not mean that part is automatically bad. As said above, further diagnosis is almost always required. But, given the cost/hassle of hiring a pro, it CAN sometimes still be 'practical' to change inexpensive, and maybe even moderately-priced parts while trying to troubleshoot our own cars. After all, even if you 'guess' wrong, you probably replaced a tired, old part with a new one and eliminated that part of the system as a failure. but, sometimes a code will point to a $200 sensor or an $800 catalytic converter - and people find the actual problem was some rodent-chewed wiring that can be repaired for a few dollars, or a hole in the exhaust that can be welded-up for $50. Other people may pay a GOOD mechanic to diagnose the car, then pull it back home and repair it themselves. many different approaches. And there's nothing wrong with having a pro fix your car. There are trade-offs in every approach, depending on your situation. Sometimes I don't have the luxury of time for extensive tear-down, even if I thought i had the skill. there's an old saw about; CHEAP, FAST ,GOOD - you can only choose 2. Quote Link to comment Share on other sites More sharing options...
sirtokesalot Posted November 18, 2015 Share Posted November 18, 2015 ive seen mine flashing twice now. once was because water had gotten down the tube where the spark plug goes and was causing a constant misfire the second time was when the harmonic balancer i think its called the main pulley that drives everything came off the engine and that caused it to flash. Quote Link to comment Share on other sites More sharing options...
ThosL Posted November 18, 2015 Author Share Posted November 18, 2015 Thanks for the feedback. I drove my sister's car and same thing first time in the morning, cold start, goes up hill, CEL flashes, engine loses power. Numerous mechanics have already looked at the car and could not get to the root of the problem!!! One changed a fuel injector, to the tune of $250; another did a tune up with change of spark plugs and wires. Same problem. Car runs like a top once it warms up for a while. Quote Link to comment Share on other sites More sharing options...
nipper Posted November 18, 2015 Share Posted November 18, 2015 SPARKLIE TEST! In the evening wet all the high voltage components with a mist of water and look for sparklies. Usually it can be solved that way. Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted November 18, 2015 Share Posted November 18, 2015 possible Engine Temp Sensor - doesn't 'choke' the car in the mornings. But I'd expect hard starting/poor idling until warm. on an older car, could be some type of temp sensitive vacuum leak. a vacuum gauge is cheap to buy, maybe free to borrow from a parts-place. Check when cold in the morning, compare to warm conditions? maybe a sticky valve in the failing misfiring cylinder? carbon buildup or dropped guide? Quote Link to comment Share on other sites More sharing options...
ThosL Posted November 18, 2015 Author Share Posted November 18, 2015 None of the mechanics have been able to figure this out; but the sister always brings the vehicle in after it has warmed up. Quote Link to comment Share on other sites More sharing options...
nipper Posted November 19, 2015 Share Posted November 19, 2015 AHA! She needs to leave it overnight, outdoors at a shop. 1 Quote Link to comment Share on other sites More sharing options...
ThosL Posted November 19, 2015 Author Share Posted November 19, 2015 (edited) The CEL on the dash went off spontaneously yesterday. I took it for a drive this morning--no problems whatsoever. The problem comes and goes, but seems to come on in the morning. Also I saw the tell-tale drip coming out from under the water pump, I added fluid to the overflow tank as it was low; I don't think a water pump issue would trigger a CEL. Again, a 96 Wagon with the 2.2. Edited November 19, 2015 by ThosL Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted November 19, 2015 Share Posted November 19, 2015 check inside the radiator - don't rely on 'just' the mark on the o'flow tank. system can be pressure-tested. might confirm the waterpump. or bypass hose w'ever. wonder what the code was that triggered the CEL? misfire still? Quote Link to comment Share on other sites More sharing options...
Trailcutr Posted November 19, 2015 Share Posted November 19, 2015 Mass air flow sensor on the airbox. I had the same issue. 1 Quote Link to comment Share on other sites More sharing options...
ThosL Posted November 20, 2015 Author Share Posted November 20, 2015 So what's the remedy for the mass air flow sensor malfunction? Also I had a misfire code on my 99 Wagon, I don't want to open thread on that. I checked the plug and reversed the wires, no change. Remedy? Thanks. Quote Link to comment Share on other sites More sharing options...
Trailcutr Posted November 20, 2015 Share Posted November 20, 2015 I had almost the exact same symptoms with my mass air flow sensor. It can't be tested but there are cheap ones online. I found two for around 30 a piece when mine went bad. Or try to clean it with some mass air flow sensor cleaner see if it works. It never worked for me. It should throw a code for it if it's bad but you know how that can be. I also had a bad knock sensor once that had similar symptoms but not so much lack of power. It kept throwing weird codes till I figured it out. Also subaru plug wires are very thin and can arc with the slightest damage. I replace all mine every year it seems before winter. Make sure you inspect them all thoroughly for any mouse chewings. One tiny tooth mark is all it takes to cause a misfire. This time of year is the most likely time it will happen with winter coming. Just a thought. Quote Link to comment Share on other sites More sharing options...
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