Disappearing CEL?

[secretdonkey]

Okay, my first post, and apologies if a little more searching and RTFM-ing would have yielded me an answer, but I didn't have any success, so...

I just had a CEL disappear on my '99 2.5 - I didn't think a CEL would disappear without resetting, so I'm puzzled. Background:

I was getting OBC-II codes 0410 and 1411, aka "Secondary Air Injection Signal Implausible" with each code corresponding to a cylinder bank. Per a good online article, I tried cleaning the MAF and pulling the battery to reset the CEL, but it came back.

But now it's gone away. I haven't driven enough to see if it's going to come back, but I have a suspicion that electrical gremlins may have reset the code for me. It's been rainy and I had not driven the car for about two weeks. Strangely, I found that my key remote wouldn't open the trunk or unlock the door. I used the key to unlock the door and inserted the key and everything was back to normal after that. Radio works fine, so if there was a power interruption it didn't trigger a radio code reset. Also, the CEL bulb is not out because it illuminates when the key is in the proper position.

Can a CEL go away if sensors haven't sent an error message in awhile? Is it possible I had a brief power interruption and the code will likely return? Any ideas?

Thanky thanky in advance for any ideas!

[Orient Express]

All OBDC error codes stay in the ECU memory until cleared, but some will allow the CEL to rest if they are intermittent and do no reappear after N number of driving cycles. Any error with "implausible" in the description are typically intermittent and will usually allow the CEL light to go off after a number of driving starts. It is still in memory, and should be cleared to see if it will reappear. If the Secondary air pump does not come up to full pressure in a given time, it will trigger the fault, but it is usually an intermittent borderline case. Cleaning the MAF and disconnecting the battery will have the same effect as dancing a jig on one foot, and howling at the moon.

[secretdonkey]

Ahh, thanks! The online article I referred to was indeed careful to mention a dirty MAF was an unlikely trigger for those codes. Since cleaning the thing cost me next-to-nothing to do and since the closest shop with full manuals and a Porsche code tester is about 100 miles away, it was worth a shot. Looks like I got lucky - I had been living with the CEL for the time being since I noticed no change in performance, but having it staring at me and feeling the need to keep checking to see if any additional codes were present was not my idea of fun. :)

All OBDC error codes stay in the ECU memory until cleared, but some will allow the CEL to rest if they are intermittent and do no reappear after N number of driving cycles. Any error with "implausible" in the description are typically intermittent and will usually allow the CEL light to go off after a number of driving starts. It is still in memory, and should be cleared to see if it will reappear. If the Secondary air pump does not come up to full pressure in a given time, it will trigger the fault, but it is usually an intermittent borderline case. Cleaning the MAF and disconnecting the battery will have the same effect as dancing a jig on one foot, and howling at the moon.