asc0205 Posted January 28, 2015 Share Posted January 28, 2015 My CEL came on the other day so I put the car in the "diagnostic mode" and it's giving me the following codes, P0500, P0021, P0420. It also gives me C0105, C0107, and C0108 but these were showing before the CEL was on so I am less concerned about them. Can anyone tell me possible causes of the P codes? I mostly want to know what the P0420 code is for. Link to comment Share on other sites More sharing options...
travrach Posted January 28, 2015 Share Posted January 28, 2015 PO420 is Catalyst Efficency Link to comment Share on other sites More sharing options...
asc0205 Posted January 28, 2015 Author Share Posted January 28, 2015 Does that mean I'm looking at a cat replacement or could it be an O2 sensor? Link to comment Share on other sites More sharing options...
travrach Posted January 28, 2015 Share Posted January 28, 2015 Generally a PO420 code is the Cat, but it should be checked by monitoring the rear o2 and see what it is reading. Warm car up to operating temp, hold throttle at 2,000 RPM, watch rear o2. It should remain low voltage, less then .5 and fairly steady, if it's jumping around that means the Cat is not doing it's job. However the car should be in proper running order to do this test, so you should look at others codes 1st also. Everyone hopes it's just a sensor, but if the sensor was bad it set a code for the sensor! Can it be slow and old maybe, if you replace the sensor only it "may" help for a period. Bottom line is fix any running issues 1st then have the Cat properly checked. Link to comment Share on other sites More sharing options...
asc0205 Posted January 29, 2015 Author Share Posted January 29, 2015 Okay that makes sense. Can someone explain the other P codes? From what I can find the C codes are for wheel speed sensors and those don't seem to be affecting anything. Link to comment Share on other sites More sharing options...
Rhitter Posted January 29, 2015 Share Posted January 29, 2015 P0500 http://engine-codes.com/p0500_subaru.html http://www.subaruoutback.org/forums/66-problems-maintenance/23109-transmission-threw-code-p0500-speed-sensor.html P0021 http://legacygt.com/forums/showthread.php/help-p0021-intake-camshaft-position-timing-over-advanced-18887.html http://legacygt.com/forums/showthread.php/dreaded-p0021-181887.html What's up with all your sensors? My OBXT build Link to comment Share on other sites More sharing options...
asc0205 Posted January 29, 2015 Author Share Posted January 29, 2015 Man I wish I knew. On Saturday night after I did the brakes with my dad at his buddys house, we attempted to make it up his snowy unplowed driveway and did plenty of spinning in the process. When I finally gave up (only after two attempts) my ABS light was on with the CEL. I just let it be assuming the sensors were packed with snow or really wet or something. In the morning I went down and checked the codes but the ABS light had gone off. After a trip around the block with a couple of stops and restarts, the CEL cleared as well as all but the C codes. Later that day as I was headed home the CEL came back on and gave me all of the codes listed in my first post. Assuming the P0420 and P0021 are unrelated, could the other codes be related to this event? Link to comment Share on other sites More sharing options...
asc0205 Posted January 29, 2015 Author Share Posted January 29, 2015 Okay here we go. Brought it in today and all but the P0420 code were just duds. The P0021 was supposedly on because of low oil at some point( it looked good when I checked multiple times). The rest are wheel speed sensor codes that meant nothing. The bad news is I need the rear most cat and O2 sensor. Luckily I'm still protected under the Massachusetts Lemon Law and the previous owners are paying to have it all fixed. Link to comment Share on other sites More sharing options...
sunny5280 Posted January 30, 2015 Share Posted January 30, 2015 Okay here we go. Brought it in today and all but the P0420 code were just duds. The P0021 was supposedly on because of low oil at some point( it looked good when I checked multiple times). The rest are wheel speed sensor codes that meant nothing. The bad news is I need the rear most cat and O2 sensor. Luckily I'm still protected under the Massachusetts Lemon Law and the previous owners are paying to have it all fixed. Curious...what is the highlights of the Massachusetts Lemon Law? Link to comment Share on other sites More sharing options...
asc0205 Posted January 30, 2015 Author Share Posted January 30, 2015 Curious...what is the highlights of the Massachusetts Lemon Law? Not exactly sure what you mean by that but the law says if you buy a car and it won't pass inspection, the previous owner is required to pay for any repairs necessary for the car to pass or they can take the car and give you your money back. This only applies to cars you purchased in MA and it must be within 30 days of purchase. Link to comment Share on other sites More sharing options...
sunny5280 Posted January 30, 2015 Share Posted January 30, 2015 Not exactly sure what you mean by that but the law says if you buy a car and it won't pass inspection, the previous owner is required to pay for any repairs necessary for the car to pass or they can take the car and give you your money back. This only applies to cars you purchased in MA and it must be within 30 days of purchase. That's what I was looking for. Thanks for the summary. Does this apply to private party sellers too? Link to comment Share on other sites More sharing options...
asc0205 Posted January 31, 2015 Author Share Posted January 31, 2015 That's what I was looking for. Thanks for the summary. Does this apply to private party sellers too? The law applies to both private party and dealer sales. The dealer laws are a little more complicated. The car must have cost more than $700 and have less than 125,000 miles. The dealer is also required to attach a sticker to the car window that describes the law. Link to comment Share on other sites More sharing options...
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