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.
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
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 "experienced" parts
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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