2002 24V w/Auto Trans.  All Stock.  The past 2 weeks have been riddled with an intermittent Check Engine Light, Erratic shifting and a Voltage gauge going from just over 14V down to nothing, triggering a Check Gauges warning light, then within seconds the gauge climbs to 12-13V and the Check Gauges light goes out.  The intermittently flashing CEL usually coincides with erratic shifting and hunting of the lockup converter or what feels like clutch/band slippage in auto tranny.

Started with checking the batteries (Good), checked the Field wires from PCM to Alernator and the PCM was not sending signal (Dark Blue wire).  Continuity test of the dark blue and the green wires from the PCM to the plug at alternator were good.  The 140A fuse is good and there is 12V power to the back of the alternator.

There is no Crank Position Sensor on this Cummins.  (I found out after removing the Starter...stupid!).  So, to rectify the P0320 code, I replaced the Camshaft Position Sensor. (That was not fun...)

This led me to believe that the PCM was faulty.  Ordered a replacement and swapped it out per instructions yesterday...

Cleared codes and P0320, P1682, and a new code P1899 showed up.

This is my daily driver and only vehicle.  I am stumped.  Please Advise

Gunny.

Did the weird charge issue go away after replacing the PCM?

 

Here is some info for the 1899 code.

 

As above, do the diagnostics for the P1899 code, where did you get the pcm from ? ACS hopefully.

Have you done the WT mod ?... sticky at the top of this section, have you checked AC voltage as per WT article ?

So, PCM from Car Computer Exchange - Used them for a '90 Dakota and had good results.  The PCM did not solve the charging issue.  I have not yet done the WT mod.  My worries is the erratic shifting and the truck trying to start out from a stop in 2nd or 3rd.  I have been manually shifting and keeping it below 35 with light throttle load ( I am down to this as my only vehicle).  

Truck was in the shop today (ICDI Diesel) to get a professional and fresh set of eyes on it.  They stated that the ECM & PCM were not communicating and there may be a fault in the wiring between the two.  They did not have the time to track it down and asked me to bring it back on Monday to complete the job.  

I will look into the WT mod and may take that monster on over the weekend.

In the meantime I will tag @Dynamic on the shifting issues. 

Sounds like a power distribution problem somewhere. Not sure why the PCM was condemned, but even if the alternator quit charging altogether, the gauge wouldn't drop to zero. Somewhere in the power distribution system, there's a faulty connection. The transmission can't work with no electrical power.

On 6/17/2020 at 12:31 PM, Gunny said:

Voltage gauge going from just over 14V down to nothing, triggering a Check Gauges

 

When the actual battery voltage goes from 12.00 Volts to 11.99 Volts it will set the check gauge light and the volt gauge will fall to 8 Volts even though the voltage is 11.99 Volts and this is normal function. 

 

On 6/19/2020 at 7:35 PM, Gunny said:

I have not yet done the WT mod.  My worries is the erratic shifting and the truck trying to start out from a stop in 2nd or 3rd.

 

W-T ground wire mod is REQUIRED. This will fix the shift issues and electronic noise issues.

 

On 6/19/2020 at 7:35 PM, Gunny said:

They stated that the ECM & PCM were not communicating and there may be a fault in the wiring between the two.

 

No most likely not. If the alternator is damaged and creating large amount of AC noise it will flood the entire system including the CCD network that allows all the computers to talk. But it like screaming over a loud room of people, then there is a guy in the room make tons of noise flooding out the conversation and now the computers can hear whats being said between each other. 

 

Replace your alternator and test your new one BEFORE you leave the store.

Do the W-T ground wire Mod.

Do the PCM protection fuse Mod. 

Send your PCM off to Auto Computer Specialist. Let them test and repair your PCM. I'm also a customer after my PCM was fried by a bad alternator. 

 

After I've done this alternator and charging problems all STOPPED!

 

Thank you all for your Input.  I will follow your instructions completely.  Next up - WT mod. Then PCM Protection Fuse.  New alternator is on the way...

Gunny