Pulling my hair out here.... 99XJ 4.0- Have the classic no voltage gauge and fuel gauge along with no start. Stays the same with Cam,Crank,Map,TPS unplugged. Im only getting 3v reference to the sensors as well. Will not communicate with scan tool as well. Previous owner has changed PCM twice and says that it runs for a few days then dies with same symptoms again. I have a pcm to swap in but am worried that it will end up fried again. Any suggestions on what could be killing PCMs in this thing? What circuits could possibly cause this?
Bad PCM Multiple times??? 99Xj
- Thread starter xjlife01
- Start date
lawsoncl
NAXJA Forum User
- Location
- North Idaho
I would narrow the problem down first, under the assumption that the PCMs are actually still good. Have you tried unplugged the connector for the clockspring? One common failure is the clockspring wires shorting against each other causing problems. Otherwise, I'd start backprobing the PCM to see of anything looks unusual, in particular wires that are supposed to be grounded are in fact grounded.
- Location
- Minneapolis, MN
Classic CPS fault symptoms, but it may be more than a simple failed CPS.
Suspect wire harness defects shorting out the 5 volts CCD Bus. Any of the OBD sensor wires could be the root cause. Don't forget to check the O2 sensors and wires.
Horn circuit shorting to the TPS circuit is a logical suspect. Failed wire splices and failed wire insulation are other good suspects.
