Clearing MAP sensor code
Yesterday while I was repairing the door hinge on a friend’s Jeep Cherokee, I noticed it had been running rich. I checked the ECU codes and found code 13 and 52. 13 is an unresponsive MAP and 52 is O2 rich.
I first swapped in a spare MAP, cleared the codes and started it up. I got he same rough idle and soon the same code in the Check Engine light.
With the engine still running, I pulled off the vacuum line and noticed there was no vacuum. The line looked fine. I pulled off the other end and found vacuum at the manifold. The line was obviously clogged.
As I was walking to pull a spare off the parts rig, I noticed a tiny spot on the bottom of the line that was melted. I never found the source of the melting, but the Jeep ran much better after replacing the plastic hose. The MAP and Rich codes cleared up as well.