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Discussion Starter · #1 ·
I have a 2001 Jeep cherokee sport 4.0l 4x4 that has a P0351 code. I have access to all data and have done all the test it says. Cylinder 1 and 6 have no spark so coil driver one circuit is my issue. When probing the terminal coming into the coil rail, The wire for driver one stays light on a test light constant while the other 2 drivers pulse. Ive checked resistance on power and ground side and they pass. any ideas? Also, it will not rev past 3000rpm it goes into fuel cutoff mode. If i cycle the key it will run for about 2 minutes normally. fuel pressure is constant 50psi. PLease help!!
 

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The lost spark ignition uses 1 coil for 2 cylinders, 1&2 3&4 5&6. Firing order is 153624. If cylinder 6 has no spark also then I think it's more with the pcm and the driver signal to the coil. If the coil was bad, 2 cylinders would be down.
 

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Discussion Starter · #3 ·
Cylinders 1 and 6 fire together then I believe 2 and 5 and 3 and 4 on these waste spark systems. Ive ruled out the coil and have it down to the driver circuit. Cylinder 1 and 6 neither have spark. A pcm would make sense but what doesnt make sense is why cycling the key temporarily fixes the issue also trying to rule out anything else before spending the money on a pcm.
 

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I attached the PCM's start up sequence, The engine starts in open loop (uses predetermined inputs) after it reaches operating temp it goes into closed loop and waits for input from the sensors. And I stand corrected. You are right. The coils are 1&6 2&5 3&4. So if the coil or driver circuit is bad for coil 1 it will also take out cylinder 6. And obviously, the driver circuit should pulse and not be steady. The driver sircuit for coil 1 is A7, Connector A pin 7. I would probe behind connector A at pin 7. If you get a steady light then I would lean to the PCM. Only because the other cylinders and coils are functioning normally. I included the diagrams from ALLDATA. I know you have them but this is for the benefit of others following this thread.
Circuit component Schematic Font Parallel Engineering
 

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