debdeblee: @dodgeforum.com Hello! i have a 1996 dodge ram 1500 4X4 5.2 truck 160,000 engine has new ac delco plugs and wires,cap and router,pick up coil,crank sensor,new pcm, Truck runs sometimes for 1 hour and sometimes for days and then starts back firing no power gauges jump back and forth in cluster, has P1391 code, any ideas on what to check next???cant remember but there was more codes but everytime i replace something i could get rid out those codes but the P1391 stays not sure what this code is from

 

P1391-Cam or Crank sensor signal is intermittent or missing

Enabling conditions: Engine running over 7 seconds, the alignment of the cam signal does not agree with the crank signal, the MAP reading indicates a drop in vacuum from previous operation.

Blocking action: This code can block the following monitors: fuel control, 02 monitor, catalyst monitor, misfire monitor.

Testing: Check for erratic cam and crank signals for 0 to 5 volt digital signal. The crank sensor pick up signal is on the GY-BK wire going to PCM pin C1-8. The Cam pick up signal wire is TN-YL going to PCM pin C1-18. Both sensors share an 5 volt reference supply (VT-WT wire coming from PCM pin C1-17).

The sensor ground for both pickups is a BK-LB wire going to PCM pin C1-4.