Grounds and other interesting problems....

[HiwayDiesel]

My 2000 6.5 C&C (265K miles) developed a range of problems last week: Odd noises, bucking, stalling, SES (MIL) light actuation, a whole range of codes. Following the info learned here, I cleaned the battery grounds and positives and then the ground connection at the RH rear of the intake (this was loose and had corrosion). I also cleaned the PCM connectors with CRC QD Contact Cleaner. This procdecure cured all the problems. I believe the problems were related to the PCM Ground (G201?) being loose and corroded. This alone makes a subscription to this page with the info.

At the same time my 1998 6.5 C&C (264K miles) developed a similar, but less dramatic problem. Going down the road it would lose power momentarily, flash a Service Throttle Soon light and then go back to operating nicely. We had a separate problem with a fuel starvation problem that we found out was related to a partially clogged pickup "sock" that was due to really bad fuel, which was in turn related to fuel shortages in this area in September and October 2008. After replacing the "sock" we were left with the STS/no throttle problem....and we cannot pull codes or communicate with the PCM.
We replaced the PCM and the harness from the firewall harness to the IP in August due to the wiring insulation's total disintegration due to 10 years of sitting in a valley full of..."goo".
Here is what we have done so far:

-Replaced pickup "sock" and checked tank for debris/contaminants
-Replaced "O" rings in pickup fuel line connectors
-Swapped out the lift pump with known good one
-Changed the fuel filter and cleaned fuel manager
-Checked flow and pressure from "purge line" front of engine ... 4 psi and good flow
-Cleaned and check all grounds (rear of intake, batteries, Datalink ground lower LH of instrument panel)
-Swapped out APP (pedal) with known good one.
-Cleaned three plugs into PCM (one with a nice dose of coffee or coke)
-Cleaned two other nearby plugs.
-Checked wiring leading from PCM to Datalink connector using VOM: Data, +5 reference and grounds, verified power and grounds to PCM
-Swapped out the PCM a known good one (did not start truck) to see if we could communicate...no dice

All that and still can't get PCM to communicate with Autoenginuity (laptop). Same setup will connect to my '98 K2500 gas and to my '00 & '97 6.5 C3500s, no problem.
Truck runs like a top until the STS pops on and the truck goes to idle. Then you push the pedal and away you go.

I am considering an exorcism. Does anyone have any ideas on this problem, or know a priest that speaks 6.5?

[zig9765]

pin #16 on your dlc should have 12 volts it could be fused with your cigarette light if it doesn't your scanner will not communicate

[HiwayDiesel]

I believe we had the 12v present, but just not enough amperage to read. We think that one of the employees had accidently given the fuse panel a coffee or latte baptism and while it would allow enough voltage pass thru the fuse to read 12v, it did not allow enough amperage to actually power the DLC. Sometimes it would interrupt enough power to cause problems with the PCM. After cleaning ALL of the fuse legs in the panel and the fuseholders, Mr Diesel was all happy again....except.....

the truck would run 8 hours and then start acting like it was running out of fuel. I made sure the tank was above half and started looking at the fuel system from tank forward. After the truck had sat a few hours I checked the fuel pressure and got 4 psi at the front purge drain. Then I pulled the sender/pickup and found the "sock" was clogged and the sender "O" ring had deteriorated. We had replaced the sender about six months before with an aftermarket (Specter or Spectre) and the sock was much smaller than OEM. I cleaned the sock (no replacement readily available), installed a new "O" ring and sent the truck out again. Same problem occurred. Evidently the deteriorated sender "O" ring (the big one) had allowed bit of water into the tank, which started corroding the tank and sending bits of rust into the sock. I drained the tank, scraped out the corrosion (ordered a new tank) and replaced the sender with no sock. Truck is running happily now, waiting for a new sock, a new tank and then a new fuel filter.

Life is never dull with an elderly diesel....