98 3500 dually 12 valve. dash was intermintely dropping out. codes 920 and 921 speed and pulse signal. 999 test dash functions fine. Just noticed that I'm not charging as well. Seems related but alas I'm not a dodge guru. any thoughts?

Thanks

Any standard error codes on the OBDII port?

it cannot establish communication . P/S  a/c wont engage and it feels like torque convertor is acting weird  

going to check output shaft sensor for magnetic debris.

 

Thank you for the time .

 

Being there is no communication with the PCM, every connector checked, all pristine clean, all grounds good. would it be a fair assumption that the PCM is at fault?

Can the CTM play an role in these symptoms as well?

Edited October 2, 20186 yr by Phil

INSTRUMENT CLUSTER FAILURE MESSAGE:

920    The cluster is not receiving a vehicle speed message from the PCM.

921    The cluster is not receiving a distance pulse message from the PCM.

You can disconnect Central Timer Module for testing just to rule it out, unless you have alarm enable the truck should start no problem.

Sounds like Issues with PCM, have you seen (NO BUS) message on the instrument cluster ?

 

Makes sense, does start with CTM disconnected . Have not seen (NO BUS) on dash.

looking on line for PCM  

 

Thanks Chris

Thanks Michael

Who is a good source for PCM, what options are out there?

Thanks

 

Follow up to this repair. All conversations led to what appeared to be a PCM issue. PCM was sent out to the recommended rebuilder from this string,who of course bills up front. They had great turn around time. Sadly, they couldn't or wouldn't tell me what was wrong with the PCM, just that they had "rebuilt" it. Unfortunately, it did not solve this issue.

Now assuming "yes I hate that word too" the PCM is OK for sure. It was deduced that the all of the affected systems rely on knowing that the engine is actually running and of course leads to what should of been dealt with first … Crankshaft Sensor. Lesson learned from my 30 years in gas engines... most of the time, unless there is a specific high frequency of PCM failure, its generally not the PCM. Fortunately, my issues have lead me to find this site, Thank you to all who have helped!! 

 

PS

(cant figure out why PCM is underlined through this post)

Edited October 29, 20186 yr by Phil