Heard starting need some help!

I have an Volvo vnl780 2007 with about 638,000 miles on it


I am having a hard time getting the engine to start sometimes, ( Most of the time) used to start up in about three seconds, now it takes 10 to 15 seconds for the engine fires.


I check the codes in the display this is what I'm getting,


Mid 128. Sid. 21. Fmi 3 Engine position sensor?

Where exactly is this sensor located, is it at the front of the engine or on the bell housing on the back of the engine.


Any help would be appreciated the last thing I want to do is take this Truck to Volvo.

 

Well, I'm getting closer to my problem I think, I headed down to the Volvo dealership parts department since the service department was closed on the weekends. On a D12 there are two positioning sensors, one sits on the cam the other sits on the bell housing looking at the fly wheel, both sensors are exactly the same.

I took the bell housing sensor off and cleaned it and put it back together and start the truck, it started the same way as usual 10 to 15 seconds before she fire up. And the code appeared in the display
128. 21. 3

So I proceeded to remove and replace the cam sensor, ( aka position sensor ) five hours later, I had her back together. I cleared all the codes in the display, started the truck, started up in about five seconds but the code reappeared back in the display. 128. 21. 3. So it looks like it the fly wheel sensor or not.

 

After fixxing one problem I got another, now it's saying that it's the flywheel sensor or the speed sensor, all three sensors work in conjunction with each other. That what I find on the Internet searching through Google's, has anybody else experience these kind of problems.

Any help would be appreciated.

 

D12 Volvo 2007

 

Okay here's an update, I checked both Positioning sensor, one at the flywheel other is on the cam, both sensor have ohms between 500 to 700, both checked out at the main trunk line on the ECM.


It could be the main ECM has a bad driver Chip on it, or one of the flags broken off of the cam shaft, ( I highly doubt it ) I won't know any of this until i bring my truck to volvo , look like they have to hook the computer on to it, While the truck is being started so they can see if the sensors are all talking to the ECM


Does anybody have any other ideas or any comments would be appreciated


Look like this is going be a big dollar job

 

Update

Buckwild was right, the crank sensor was bad from Volvo ( an brand new part from volvo ) I installed another crank sensor, the truck fired up in two sec. after turing the key on.