You need to plug a voltmeter into your front cigar lighter or power point so you can monitor the voltage while you are driving to see if it suddenly goes up.
I had this problem on my 2002 Export CRD whereby I could see that the voltage would rise up to about 17 volts whenever I turn on the front wipers or turned on the air con.
This caused a "ping" to occur and would power the Jeep down...also fried the battery.
I traced this to some wiring problems...probably damage caused to the wiring up front from an incident with a tree...I ended up replacing 5 wires all in.
I agree with tkj2002 to check the wiring going to the alternator but on the 2003 KJs this is not a "Trigger" wire but rather a pair of wires that carries varying voltage to power the field coil in the alternator. The one wire goes direct to +12 volts when the ignition is ON and the other wire goes to the PCM which switches this wire to ground in varying pulses, Pulse Width Modulation, to vary the period of the ground being sent to the alternator field coil. If this wire is shorted to ground then you get continuous 12 volts applied to the field coil and the voltage rises.
I also had a problem whereby the SKIS light stayed on solid and I had to jumper pin 30 and 87 in the ASD to get going. In my case it was because the one lead going to energize the ASD relay had broken so although the PCM (ECM for CRD) was happy with the SKIM signal from the chipped key...the ASD relay did not energize. In your case perhaps the ASD relay is not being energized because the PCM is not happy with something...maybe the PCM is picking up that the field coil is being energized full time as soon as ignition is turned ON.
I will have a look through the 2003 circuit diagrams to check which wire on the alternator should have +12 volts on it and which should be the varying ground....you can pull this plug off the alternator and with ignitio ON... one of the wires should show +12 volts while the other wire should be floating.
You could try disconnecting the battery and pull off the connectors to the PCM. Then apply a hair dryer to the connector and PCM contacts to dry them out.....do the same with the Alternator connector.
If you do not have the circuit diagrams for your KJ you can download the Service Manual for your year KJ here...includes all circuit diagrams..have fun!
Index of /manuals/Jeep/KJ
