Hello everyone, new to the forum. Have a problem with the tach and check engine light. Have codes P0341, P1690, P1689. Have tried several things like taking to the dealer and having it checked out, but to no avail. Have changed the cam sensor twice, have taken the injectin pump off and sent in for check up was good. have cleaned all connectors and wire harness. Not sure what else to do. Has anyone heard of this. Rough idle will go away if cam sensor is unpluged. And rpm drops to zero under a load, but when throttle is lifted the rpm comes back.

 

could be your ecm!

 

Thought about ECM, slaved one in and no difference in the idle. Did not drive because just slaved in to check.

 

might have something to do with the tpps..?

 

The APPS usually won't throw a code.

You can try an APPS reset and see if it cures it, but it will only be temporary if it is the APPS itself.

Search it and try the procedure, its simpler than some of the stuff you have already tried and shouldn't need more than a multi-meter and a little patience....

 

Tried a different APPS at the dealer that they had was still doing the same thing. Not sure whats going on now. Something is interferring with a signal somewhere just have to figure out.

 

I have read that the alternators on our trucks can put out a lot of interference....There is a shielding method discussed in some of the "auto trans hunting gears" threads

 

Could try and leave it running and start tugging on the engine wires to see if someting happens?

 

I noticed you have an aftermarket camshaft listed in your signature. Have you contacted its manufacturer about possible known issues? It's always possible they have seen issues with sensor clearance or the like.

Seeing a difference in tach operation between load and coast makes me think there may be end play that is letting the sensor clearance change beyond spec.

 

Thought about that and did tug on all the wires, too no avail nothing changed, thanks for the input. Still scratching my head.

 

I have throught about this a great deal and lean in that direction also, but the cam has been installed for a while now and should have started right away after installition I would think. But rpm falls and comes back under load, but never falls without a load. that is what is confusing.

 

Thanks will check it out

 

its the Cam sensor under the VP not fun to change

 

Tried two of them just incase one was bad out of the box, joe no good still does the same thing. It has to be electrical or ecm. Hate to buy ecm and that not fix it. Thanks

 

how old are your batteries? Have you checked fuel pressure, clogged filter,air intake. any smoke from exhaust, valve set? grasping straws here??