So the past few days when I drive my truck The tach will sometimes bounce around until i let off and it idles then it will work and stay perfect still. Then I go to give is gas again and it works then all of a sudden bounces around then works. But just yesterday it seemed it was idling a little more i guess choppy than normal then seemed to run better later on after it was shut off. I put a code reader on it and got p0336 which is crank sensor A circuit range/performance. Also got p1690 which is a guess a communication error with the ECM and crank sensor I think. So should I just replace my crank sensor? Is there anything special you have to do other than remove the starter? cause i can see it its right behind it. thanks for any advice

I would remove neg. cables first. Other then that no speical items. Did mine 6 months ago no more problem with tach. Maybe instal a set of larry B's starter contacts while starter is off truck. Mine was not having any problems but did any ways. Glad I did the contacts where half gone. Saved myself trouble down the road. Geno's also has the contacts about 60.00' easy install.

I think I had those same codes when I was installing my fuel system and the new wiring harness for the carter pump and hobbs switch. Choppy idle and tach bouncing but fine when I was driving...I'm sure Michael will chime in but a wiring or electrical issue could be present. PS, as stated above, if you take the starter off a rebuild kit from Genos is worth it!

So the past few days when I drive my truck The tach will sometimes bounce around until i let off and it idles then it will work and stay perfect still. Then I go to give is gas again and it works then all of a sudden bounces around then works. But just yesterday it seemed it was idling a little more i guess choppy than normal then seemed to run better later on after it was shut off. I put a code reader on it and got p0336 which is crank sensor A circuit range/performance. Also got p1690 which is a guess a communication error with the ECM and crank sensor I think. So should I just replace my crank sensor? Is there anything special you have to do other than remove the starter? cause i can see it its right behind it. thanks for any advice

I would start with the crank sensor first... Typically the P1690 code comes from lack of crank sensor signal.

P0336

http://articles.mopar1973man.com/2nd-generation-24v-dodge-cummins/59-obdii-error-codes/175-p0336-crankshaft-position-sensor-signal

P1690

http://articles.mopar1973man.com/2nd-generation-24v-dodge-cummins/59-obdii-error-codes/229-p1690-vp44-ckp-sensor-does-not-agree-with-ecm-ckp-sensor