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Suggestions on where to look

1K views 7 replies 5 participants last post by  Jcart 
#1 ·
Yeesh....she's wearing me down...

Hey everyone,

Seems I have an intermitent power to the PCM (I think) and yes I will pull my chip tomorrow.

Went for a drive, found gravel road to see if I could shake up anything....nothing...back to pavement and CEL comes on but does not stay on. WTS light cylces on off, fuel peddle goes dead, then she fires up...quits and it seems if I feather the peddle it will run...limped it home....DTC P0470 (which stays on constantly) and P0603 which will clear.

Chip is new and I was very careful at cleaning (acetone finger nail polish and fine fibre pad) used dialectric grease on install.

If after I pull the chip and there is no difference, any suggestions on where to track this intermitent power problem????

Becoming..well...frustrated as the wiring harness looks intimidating....and was wondering if anyone else has had this problem?

sorry for the long note...just kinda bumin'....

jrc
 
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#2 ·
Have you checked the valve connections for loose or burned ..Check under the valve covers also.....
 
#3 ·
Hey Rick,

Yes I R&R'ed all the connections on the VCG and VUC earlier this spring and replaced:

HPOP
IPR
IDM
PCM

jrc
 
#4 ·
I read a thread here a while back about a bad wire under the power distibution under the hood... It caused a no start , but yours may be heading that way

Have you changed the CPS yet ?...
 
#5 ·
Looking in the diagnostic manual, here is what I found:

P-0470=Exhaust back presser sensor circuit malfunction. One of the possible causes listed is a faulty PCM.

P-0603=PCM power interruption. The power is supplied through fuse #9. Look in the scamatics and find everything that is run off of fuse #9 and make sure there is not something else drawing the power down. If there is nothing else than the PCM, your PCM may be failing. You need to verify that all the wiring supplying power to the PCM is OK
 
#6 ·
fuse 22 also powers the PCM.
 
#7 ·
AND, maxifuse #22 also controls the fuel heater element in the bottom of the fuel canister. I've never heard of a bad heater element causing an engine to run poorly; it'll just short out and blow the fuse, killing the engine. Still, it's worth a look... perhaps fuse #22 is loose or damaged, yet not blown (with these trucks, I'd believe anything)...

Josh
 
#8 ·
Thanks for the suggestions and support Guys.

Pulled the 42 pin connector apart looks good. Pulled the underhood fuse block apart inspected, (bottom side and B+ bus connectors) put in some dielectric grease (sparingly) on maxi fuse contacts.....no chaffed wire, corrosion. Pulled apart PCM plug and inspected nothing...and used dialectric on the all the female pin connectors.

Pulled the chip re-installed and shimmed the PCM inside the hold bracket so it would not rattle. fired it up and has ran great thus far?

Jury is still out.....hope it was just a poor connection that I got fixed. /ubbthreads/images/graemlins/shrug.gif

got to run it up some gravel road...

Thanks again,

jrc
 
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