P01391 Fault Code Jeep 4.7

2000 Jeep Grand Cherokee 4.7 has a P01391 (intermitant cam / crank sensors) fault code. Jeep runs great, never stalls and always starts. Cam sensor was replaced (not mopar) and same problem. I have an Autel MS906BT scanner and just recently purchased the MP408 (4 channel scope) for it.

When I did a trace on the cam & crank sensors and compared to a 'known good' trace for the same 4.7 engine, they are identical. I cleared the PCM memory and then I made several drive tests (short and long) after clearing the code each time. If I drive 5, 20 or 40 miles the P01391 code never sets. If I shut the Jeep off, the next time I drive it the fault is not set until I drive a couple miles and then its back.

My next step is to connect leads to the cam / crank circuits, run a long USB lead into the Jeep to connect to the Autel and try to record the moment the fault code sets.

Just wondering if anyone has seen a similar problem. The road tests were done on days when the temperature was 60 degrees and others when it was 90 degrees. I even tried to recreate it in the garage standing still when the engine was so hot the electric fan kicked in to keep it cool.

Dhuffman wrote: My next step is to connect leads to the cam / crank circuits, run a long USB lead into the Jeep to connect to the Autel and try to record the moment the fault code sets.

I think you have the right Idea. Try wiggle-testing the wiring harness. The SET CONDITION for this code is when the failure counter reaches 20 for 2 consecutive trips. That means on the second trip when the code sets and the light comes on, the failure has already happened 20 times during that trip.

It will be hard to find s glitch on the signal wire so I would look for an issue on the power and ground first. Check the power by back pinning at the sensor, same for the ground, you can use a low wattage test light to load both looking for glitches on the scope when you wiggle test. If you suspect the ground try a jumper wire to ground