Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
1996 Jeep Cherokee Sport, 4.0 Inline Six
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.
Not aware of pip sensor, cam sensor is a plate that sits in distributer under rotor. AKA ignition pickup. That has been changed. No other wiring going to distributor.
No spark situation was determined at coil. (Removed cable from coil to distributor and checked for arc to ground.)
I've done a cursory inspection of cables that looked fine but at this point I'm going to comb over all wires to look for damage.
Pip is primary ignition pickup which is also cam sensor. With what you just typed I would look into the wiring to coil and back to ASD relay (test relay they can go bad) recheck any fuse related to ignition as well.
