QuestionI have a 97 cirrus 2.5L V6. I am not having any problems except the check engine light has just come on. The codes I am getting are (12), (21), (55) 1st, what do they mean, 2nd can the codes for this car be cleared by disconnecting the battery.
AnswerHi Fred,
The codes are useful, and yes you can clear them by disconnecting the battery for a few minutes, except that the 12 and 55 codes will be there again, and the 21 will return after you start the engine and drive it. That is the one that causes the light to come on.
Here is the deal:
The 12 means that sometime in the recent past the power supply to the engine controller was interrupted (such as by disconnecting the battery, otherwise there could be a loose wire that supplies its current); So that one will always be there for about 50-100 key cycles after you disconnect the battery and then it will self-erase which is how you could distinguish those two possible causes for the 12.
The 55 means "end if readout" so even with no codes you will always get that as confirmation that the there was a readout done.
The important one is the 21 code. It says that one of the two oxygen sensors is showing a malfunction. Most likely it is the upstream one, on the exhaust manifold, but the only way to be sure is to get a second readout using a diagnostic reader. I have been told the Autozone stores will often do that for free. There are four possible ways that either sensor can be at fault, so there are 8 possible four digit numbers. Rather than go thru the list, please get such a readout, talk to the person who does the reading for a translation of the meaning, and if you still have a question write me back and tell me the number. A new sensor is the likely solution, but which is the question; and it may not be the sensor but rather a wiring or a problem with another component in its circuit. So getting the 4 digit code is the key.
Roland
