Rpm drops to zero and CEL on

[xmtysonxm]

So earlier this week I put the big line kit on from my factory filter to the VP44. After checking all the connections I went to the car wash and powerwashed under the hood around the starter, whole factory fuel filter unit, and around the inlet for the VP44. 

 

This morning was 36 degrees and the truck started fine and drove about 30 miles on the freeway headed out deer hunting. Pulled up to my friends house and then the RPM gauge drops to zero, CEL on, and the truck started almost like hiccuping or bumping RPM up. Backed out and drove it down the street and the truck seemed to drive fine. Pulled over, shut it off, waited about a minute then turned it over.  Truck just cranked, wouldn't start. Bump started to see if it was a fuel issue but the gauge showed 20 psi. You could hear the pump running for the 30 seconds or whatever. After another minute or two it fired up. I drove it back to my friends house and the CEL came on again. We drove up to where we were hunting about 3 miles away. The rpm gauge would randomly drop to zero then back up where it should be. Parked it and was just praying it would work to get me home.  

 

After a very successful hunt, drove the truck about 100 yards. No CEL, parked it. Fired it up about 5 mins later. No problems.  With a bed full of deer we started to head down to town. CEL came on, RPM at zero. Truck had one or two slight bumps up in rpm but idled fine. Drove it to town to drop one of the deer off.  Didn't dare shut it off in case it wouldn't start like earlier that morning.

 

The whole time the EJWA showed I had an RPM reading but the factory gauge showed zero. Truck drove 28 miles or so without any problems with the CEL on, and then the rpm gauge came back like normal. After dropping the deer off (didn't let the truck turn off the whole time) I pulled into the car wash to wash the bed out. Turned it off, washed it out, then it fired back up. CEL was gone. No more issues.  I don't have a code reader currently but will try and stop by my friends place to see what that code was. 

 

Any ideas on what could be going on?

Crank position sensor? Harness not water tight? Is there a waterproof seal around the ECM? The weird thing was my EJWA still showed a reading.

[Mopar1973Man]

More than likely a CCD network issue being the Edge is getting Rach signal from the CANBus lead.

[Me78569]

The edge will read Rpm via canbus which likely uses the cam sensor, the cluster talks to the pcm for rpm which likely uses the crank sensor.  

 

So even though the edge reads rpm your cel might be on.

 

 

What codes do you have?

[xmtysonxm]

I checked for codes twice. Once with a small unit and the second time was at autozone. They plugged it in my truck, then downloaded it to their computer. It didn't show any codes at all. Their scanner did not show the abs/brake light that was on either.  Do I need to use a special scanner to read that code? Or do I need to go power wash it again to  make the CEL come back on then go read it?

 

How does the Chrysler crash detection affect the tach signal?  Doesn't the Crank position sensor send the signal to the ECM and from the ECM to the gauge cluster? 

[Mopar1973Man]

Crank sensor -> ECM -> CCD Network -> Cluster

 

Or it could be sent to the PCM for transmission purpose for the automatics. The CCD network just broadcast the information and the listen device will pick up the information or not depending on the need for the information. So like another example speed signal comes from the ABS module and sent over the CCD Network but the ECM uses the speed signal for cancelling the grid heaters. Then the PCM uses it for cruise control. This is the beauty of the CCD network all the information is on a common network and the devices can selectively use any data it wants.