I was having trouble with my 94 Spirit and a code 21 and the Check Engine light was on. I checked all the connections and cleaned up the ground wire for the oxygen sensor and it still threw the code. I had to drive up to the gas station and on the drive up I noticed lockup was still working, i thought it wasn't supposed to work if a code 21 was set (or am I wrong?). When I got back home, I checked my codes again and noticed it was showing a code 51 in addition to the code 21, but when I restarted the engine, the Check Engine light was out. Reading the codes section here, it says a code 51 can be caused by a bad MAP sensor. Would a bad MAP sensor also cause a code 21? I'm going to go out and unhook my battery for a few minutes then hook it back up and see if any codes are re-triggered.