Expert: Roland Finston - 8/17/2011

Question
Hi,
Have a  1991 Chrysler Imperial with a 3.3 L. Have a miss & rough idle did a code check the codes 12,25,62 & 55 came up what do these mean? l6ghg

Answer
Hi Anthony,
The 12 means the battery was disconnected from the system recently (last 50-100 key cycles). If that is not the case then the battery cable/clamp situation should be checked.
The 25 means there is short circuit in the automatic idle control motor circuits. I would look at the harness of the AIS motor which is mounted on the throttle body. It has 4 control circuit wires. The short of this circuit is the likely cause of the rough idle.  
The 62 on a different engine used in '91 says there was a failure to write data to a memory bank in the controller (it that case the mileage of the vehicle). That 62 code is not listed for the 3.3/3.8L engines, so you might want to repeat that readout and count the flashes around the point of the readout. The 62 or a 63 would probably not cause rough idle.
The 55 means 'end of code readout".
To check the idle control circuits (both for opens and for shorts) you can pull the 60-pin plug at the engine controller and measure for continuity to be present between pins 39 and 59, and between 40 and 60. At the motor plug itself you could check the AIS itself by measuring for continuity between the 2 outer pin of the socket, and then between the two inner pins of the socket. Those two sets of reading will help you localise the problem if an 'open' to either the motor or the wiring. You should also check to be sure that there is no continuity between the separate pairs of wires and between the separate pairs of socket pins as if there is, that would constitute the "short" that is identified as the cause of the problem in code 25. You could also check each of the pairs to be sure neither pair shows a short to ground (the engine block itself constitutes ground. Once you identity what is wrong you then have to locate the reason.
Roland