Re: checksum error part two

[Shannen Durphey <shannen@grolen.com>]

Sometimes scan tools can cause strange problems.  Especially when
there are several devices communicating over the same data line.  I've
seen SIR, ABS lights illuminate, false trouble codes, generally poor
vehicle operation all caused by fooling around with key on/off scan
tool connected/disconnected.  Best one seemed to be the Tech 1, worst
one seems to be Snap-on.  

Shannen
You know technology's moving along 'cause even the farmers have scan
tools.


Kelly Parker wrote:
> 
> OK I get it. the oil pressure switch is feeding the fuel pump. Just like
> it's supposed to. It took 10 seconds of reading the schematic to figure that
> out......Duh.
> 
> So what caused the checksum error. Maybe some interferance in the scan
> cable?
> 
> KP
> 
> >From: "Kelly Parker" <bigblockfw@hotmail.com>
> >Reply-To: gmecm@diy-efi.org
> >To: gmecm@diy-efi.org
> >Subject: checksum error last byte
> >Date: Wed, 07 Jun 2000 14:41:37 PDT
> >
> >I've run across a rather strange problem. I took my car for its second
> >drive
> >around the farm and upon acceleration it coughed badly. That's not the
> >strange part. I scanned for error codes and the fuel pump would not shut
> >off
> >with the key on run, engine off. I unplugged the scan cable, fuel pump did
> >exactly what it's supposed to do(ran for 2 seconds and stopped)I removed
> >the
> >fuel pump relay, no more running pump, I run pcmcomm and get checksum error
> >last byte.
> >
> >The last time I scanned the car a lot of codes flew past the screen but no
> >checksum errors. I thought I would start the car (and run it till it was
> >out
> >of gas which I thought would take about 2 seconds) when I started the car I
> >could hear the fuel pump start running. It ran until I turned it off.
> >
> >I have not reprogrammed the car since the last time I scanned it.
> >
> >With that said here is the question. Is it possible that the fuel pump is
> >somehow shorted with something else? Duh, It's obviously getting power from
> >somewhere coz' it's running. I thought I had it wired correctly but the
> >checksum error and the fuel pump thing happened at the same time. prior to
> >"cleaning up the wire routing" they both appeared to work right. Anybody
> >have any idea what happened here?
> >I do not believe it has anything to do with the checksum. I think that is
> >some strange side effect of my fuel pump wiring.
> >
> >I'm gonna go check the wiring again.
> >
> >over fueled, under scanned,
> >Kelly
> >
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