Can’t clear ECM code in self diagnostics

I have a 2005 Nissan Altima 3.5 SE-R that has had a few problems lately that I have diagnosed by placing car in self-diagnostic mode (via ignition and gas pedal method). Codes P0550 and P1273. I had the power steering sensor replaced for P0550 and bank1S1 O2 sensor replaced for P1273. I have since discovered leak in rear catalytic converter so I expected recurrence of SES light, which has happened. However I am now having difficulty confirming this in diagnostics. I follow procedure to put car in diagnostic mode, and the SES light starts flashing as expected, but doesn’t display any codes. It flashes evenly approximately 12 times then just goes solid again not allowing me to even reset it. Is this a problem with the ECM itself? Should I do a hard battery reset?

Any advice appreciated…

I suggest you use a dedicated code reader or scanner to retrieve codes. You’ll probably have better luck, versus the method you’re employing

With either, it’ll be easier to retrieve codes AND clear them, when you’re ready to do so

it could be that the code will not clear from the history until you operate the vehicle thru the drive cycle that will allow the history to be cleared.


The problem w/disconnecting the battery is that all the stored codes will probably be lost. I’m guessing the best plan – assuming you don’t want to use the code reader method – is what Yosemite suggests above, drive the car for a couple days, then re-try the diagnostic mode. Don’t replace any o2 sensors until all the exhaust leaks have been corrected, as exhaust leaks can flag o2 sensor codes, when the o2 sensors in fact are working.

There’s some possibility Nissan prevents owners from retrieving codes when it believes the problem may be a critical safety issues. Might do that to force the owner to come in to the shop for the problem. If so, suspect there may still a problem with the power steering.

Thanks for responses, I did have the dealer clear the code and the light stayed out for about 10 miles of driving. It is doing exact same thing again.

I was unaware of the CAT leak when I had the O2 sensor replaced the first time, which was done at recommendation of dealer. “Lazy O2 sensor” was what they first diagnosed, before finding the leak.

Suppose I will take it back to determine exact issue, just baffled that it won’t go into self diagnostic mode correctly. I was just hoping to confirm that the code was related to the CAT leak without paying for another diagnostic.

I’d probably stay away from that dealer. Checking for exhaust leaks is almost always a prerequisite for replacing an o2 sensor- as was stated: an exhaust leak can trigger a code that the 02 sensor is getting readings that the computer doesn’t like.

find somewhere else to go to get the cat replaced/repaired.