First and foremost, apologies for opening a non-tuning related topic. Mods feel free to move to an off-topic subforum, but the people who know what I'd like to frequent this one. I'd open a thread over at corvetteforum, but most of the members over there are non-technical Y body fanboys who know where to take there cars, and I need do-ers and hackers.
So a bit of background to start. My '95 Y body has been plagued with intermittent battery drain issues pretty much as long as I've owned it. It's progressively grown worse until finally I was able to identify the circuit reliably - CCM2 / fuse # 39 drawing ~120ma continuous. Normally it would be in the 5a range when the DAB is powered and then drop to < 10ma. Now it never drops below 100ma and will kill the battery in 2-4 days. Since I've recently expanded my collection of antique vehicles and plan to do away with my 505k mile daily driver, I need to be able to depend on this car as a backup. I just celebrated my 50th birthday, and the "gift" that comes with that milestone is that it's getting to be less fun getting in and out of this car. When I happen to forget to grab the keys, or turn said square key only to hear the starter solenoid clicking, well I've invented some new expletives for that situation.
Side story - this module is buried behind the radio head in these cars. Removing the driver's side hush panel and center console side panel are required. Also it's easiest to remove the radio head bezel and head to gain access to the connectors which have to be removed before the module will slide out. It's also probably easier to remove the driver's seat to get the center console side out. This is about a 2-1/2 hour job minimum, double that to replace all that stuff. Non-trivial to say the least.
What I know:
* The CCM looks to my untrained eye, identical to the older EPROM PCMs. In fact, under the memcal cover lives a soldered-in uv erasable eprom. I'm going to assume this is where the program code lives. I'm not really interested in reverse engineering this, but it seems like NomakeWan was able to dump this here.
* On the test bench the suspect CCM is drawing the same ~120ma continuous on the CCM2 pins (green 31 & 32)
* Replacing all the obvious SMT electrolytic capacitors changed nothing
* I bought a "remanufactured" replacement from our friends at Rock Auto. The product description said it was "plug and play, no programming required". I found this somewhat dubious, but they only wanted $110 with a $60 core so I figured what the hell.
* Upon receipt, I connected the supposedly remanufactured CCM to my test bench power supply and it draws the same ~120ma continuous.
What I suspect:
1) The "remanufactured" CCM has the same fault as my old one. Upon detailed inspection I see no evidence any internal components have been replaced and the exterior looks like it's been kicked around a salvage yard half it's life. This (replacing any components) would be really difficult to do without disturbing the conformal coating.
or
2) Whatever signal the module isn't seeing on the test bench is also absent in the car, and neither module has a fault
* The odometer, VIN and numerous other critical variables are supposedly stored within which makes me believe there must be an EEPROM chip inside
* If the remanufactured CCM is truly "plug and play", I wonder if erasing said EEPROM allows the module to automatically query the vehicle's ALDL for VIN, etc.
I finally ponied up and bought the FSM for the car so I have all the schematics. I'm willing to spend more to get a chinese clone tech 2 or whatever's necessary to progress further. Ultimately I'd love to be able to build some open-source tools to deal with these things, or just add the functionality to steveo's flashhack (forgive me steveo!). I know there's some interest among the LS / 411 swap crowd in what these modules want to be happy. If I'm going to spend money to make my car work again, I'd be happy to share what can be learned from the process.
Any volunteers?
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