Re: RE: pcm?

From: TerribleTom (silvereightynine@aol.com)
Date: Wed Jul 13 2011 - 01:04:04 EDT


On 7/12/2011 2:45 AM, Tony wrote:
>
>
> Cranks fine, it ran before he powerwashed it...
> doubt any spark, didn't check since still NO BUS error,
> prior to new PCM, relays didn't click, 0Volts to crank,Cam,MAP
sensors. basically nothing.
> new PCM, everything comes on, fuel pump cycles on as normal, have 5V
at all sensors now, but still NO guages and NO BUS. I checked the ground
on fender near PCM, is there another problem one?
>
> thanks!

Speaking from a matter of experience when it comes to trucks with
abnormally high moisture activities... it sounds like something shorted.
  "Thanks Captain Obvious"... you say... cause and effect... the fact
you toasted the PCM leads me to declare "effect" not cause. You are
still searching for the cause of what fried the PCM.

As the PCM interacts with just about everything under the hood - you
have a large task ahead of you. You are getting voltage at the sensors,
good. I suspect the sensors are good. If say you just had a bad crank
sensor and it wasn't triggering a signal when the engine cranks, - I
would say replace the crank sensor. But because there is the NO BUS
error - methinks something directly shorted out between the PCM and the
dash.

Am I correct in assuming the NO BUS error is showing up on the
dashboard? I remember seeing that pop up when I would hook up my power
programmer to the OBDII port on my Ram.

I would check the bulk head connector that bridges the harness at the
firewall. I suspect you have a bad connection between the cab and the
engine bay. It would explain the NO BUS error on the dash, it would
explain the lack of working gauges, it would explain the no start condition.

The bulkhead connector was a known issue on older Daks - no I'm not
talking about the splice of death issue from the Gen II's... The
bulkhead connections are weather proof - but not completely water proof.
  Under the force of a pressure washer - its possible water got in there.

If no obvious signs of trouble is at the bulkhead connector - you are
going to need to check wires individually to determine if there is an
open circuit. I also am not sure if the later Gen III's used fuseable
links - a check with an FSM would elaborate on that.

Regardless - my money is on a flakey or shorted connection at the firewall.

-- 
terribletom



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