1996 Jeep Cherokee Sport, 4.0 Inline Six, Automatic, NP231, Factory Tow Pkg
Second owner, well maintained. 178K miles
So here's my story, Jeep cut off while driving on the highway. No warning and had been operating great for months. Pulled off safely, had power still and would crank but no start. Got it home and the work began.
Crank but no spark. Fuel pump cycles on.
No codes. Check engine light cycles when key on and then turns off.
Inspection found rotor was toast. Like burnt up.
Replaced rotor, cap and ignition coil.
Changed the CKPS and CPS (cam and crank sensors)
Checked all fuses and swapped relays to confirm working.
My scanner communicates with PCM.
Tested for 5v signal to MAPP with key on and I get 5v. Need to check 5v reference on other sensors.
Most recently I back probed the harness to the ignition coil.
2 wires, 1 signal wire and the other should be 12v constant, as I understand. Green signal wire will light the tester when cranking but I get no 12v constant on the other wire. I believe power to coil is routed to the PDC (power distribution center) and tied to the ASD relay (which is good).
All grounds visually look good and all were replaced back in March, along with 130 amp alternator and 2 gauge battery cable upgrade. Will be going through and physically cleaning all connections next and thoroughly inspecting all harness wires.
Not sure where to go from here. Is there a way to definitively test the PCM? Even say removed from vehicle and run through a diagnostic?
Should I take a wiring diagram and start back probing the PCM?
Any help in how to work through this would be greatly appreciated.
Thanks.
Second owner, well maintained. 178K miles
So here's my story, Jeep cut off while driving on the highway. No warning and had been operating great for months. Pulled off safely, had power still and would crank but no start. Got it home and the work began.
Crank but no spark. Fuel pump cycles on.
No codes. Check engine light cycles when key on and then turns off.
Inspection found rotor was toast. Like burnt up.
Replaced rotor, cap and ignition coil.
Changed the CKPS and CPS (cam and crank sensors)
Checked all fuses and swapped relays to confirm working.
My scanner communicates with PCM.
Tested for 5v signal to MAPP with key on and I get 5v. Need to check 5v reference on other sensors.
Most recently I back probed the harness to the ignition coil.
2 wires, 1 signal wire and the other should be 12v constant, as I understand. Green signal wire will light the tester when cranking but I get no 12v constant on the other wire. I believe power to coil is routed to the PDC (power distribution center) and tied to the ASD relay (which is good).
All grounds visually look good and all were replaced back in March, along with 130 amp alternator and 2 gauge battery cable upgrade. Will be going through and physically cleaning all connections next and thoroughly inspecting all harness wires.
Not sure where to go from here. Is there a way to definitively test the PCM? Even say removed from vehicle and run through a diagnostic?
Should I take a wiring diagram and start back probing the PCM?
Any help in how to work through this would be greatly appreciated.
Thanks.
