Check engine light???

[nrossman]

My 94 YJ is throwing a check engine light. The flash code is 12. My Haynes book says that is "battery power to PCM was disconnected." I have reset the pcm 3 times and checked the battery connections and ground. Does anyone have any ideas for me or have seen this before?

[TanTJJim]

That code is nothing to worry about. As it says, it only means that the PCM has lost battery power withing a certain number of key cycles. It pretty much means the battery was disconnected at some point in time.

Now there is probably also a code 55 in the as well. At least there should be. All that code means is that it is the end of the message and no codes follow.

If there is a code that is being stored maybe you're just not waiting for the check engine light to flash the next set of pulses for the next code because at the end it should flash code 55.

I hope that makes sense. Post up if you need some clarification.