I just had to replace the Transmission Control Module on my '94 Caravan for the
second time since I got it less than a year ago. The first replacement was from
a junkyard, but solved the problem for several months. Shortly before the last
one died (causing the transmission to go into 2nd gear "limp mode") I started
having occasional battery or cableing problems that would result in slow
cranking. After the problem occured, checking the codes showed that there had
been a "battery disconnect", although I had not disconnected the battery in
several months. I am wondering if loose cables or battery "glitches" could have
allowed the voltage to spike, damageing the module that failed.
Is this a reasonable hypothesis? Would there be extra precausions to take other
than just checking the battery and cable connections?
Definitely a possibility - bad connections can cause voltage spikes.
Make sure all connections are good - do voltage drop test on all power
cables and connections - and have the battery thoroughly tested. If
the shop testing does not have a midtronics tester, take it somewhere
that does to have the battery tested.
On Jul 2, 10:34 pm, firstname.lastname@example.org wrote:
i use to use a midtronics tester biggest piece of junk tester i went
back to old school and have had zero comebacks it cannot check
specific gravity of the battery
the fault code suggests a bad connection at the battery the terminals
get a black coating and that what happens clean batery terminals and
clamps till nice and shiny and make sure they are dam tight then look
at grounds at trans make sure they are clean and tight
buying parts from a junkyard means the part you have is as only as
good as the one you are replacing
On Sun, 29 Aug 2010 14:57:05 -0700 (PDT), mrsomtingwong
The midtronics is good - very good - for most battery testing.
However, there is ONE thing it cannot reliably test for - and that is
an intermittent open circuit in the battery. NO battery tester can
reliably test for that. If it is open when it is tested, you will get
zero volts on a light load test - and a "bad battery" result on the
midtronics - If it is not open when you test it, you will get a normal
test on the midtronis, as well as on a light load test or a full load
test - and even if you could get into the sealed battery and do a SG
test, you would not get any clue that there was a problem.
Enough about the midtronics tester -
Yes, an open in the battery, or a bad battery connection, or a bad
connection in the sense wire to the regulator - which is LIKELY in the
BCM or ECM on that vehicle, CAN cause electronic damage.
As for using used parts - electronic parts in particular, I find it is
very often perfectly acceptable, and even WISE to replace with
"experienced" parts. For one thing, you KNOW it has worked, at least
once. Which is more than you can say for new replacement parts today.
The "infant mortality" rate of replacement automotive electronic parts
is way too high for my liking. When the only way to really "test"
sometimes id to replace, replacing with an unknown is a dangerous idea
- and new parts are, sadly, aften more of an unknown than
Even testing with a "known defective" part - that you know what is
wrong with - and has a different problem than the vehicle being
tested, can prove or disprove whether the part is defective. Then when
you replace with a dead new part, you know right away what you have
instead of having to chase your tail for hours, assuming you have
ruled out the defective part..
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