Further digging and research on this one. I found the problem with my 4WD not
working. The Transfer Case Control Module (TCCM) is dead.
http://dodgeforum.com/forum/2nd-gen-dakota/191088-4x4-switch-not-working-02-dakota.html
This was really helpful. With this, and the wiring diagrams from the FSM, I
pulled the dash apart yesterday and tested the control switch and the TCCM.
The switch is fine, the TCCM is bad. Unfortunately, it sounds like when the
TCCM fails, it normally fails open, so you get no +5V out of it. Mine has
failed with a short, so where there should be +5V, I'm getting +12 battery
voltage.
This post says that there's a "transformer" in the TCCM. There isn't. I opened
mine up and while there's lots of stuff in there, none of it is a
transformer. It looks more like they probably fed +12V in to a voltage
regulator to produce +5V and a bunch of heat, which is why there's a big
heatsink on the back of the TCCM. It's all surface mount stuff, though, and
covered in some kind of sealent glue, so I haven't yet tracked down the
components to figure out what may have failed. I'll be doing the junkyard
hunt for a replacement tomorrow.
What worries me now is that the TCCM is on the PCI bus. It talks to other
controllers like the PCM and the CTM. If it put +12V on the PCI bus, could it
have damaged the CTM?
The symptoms I'm having all seem to involve the Central Timing Module (CTM):
a) Weird "bing" noises at startup - CTM provides the beeper service.
b) Headlights flash - CTM controls the headlights so it can provide the
service of leaving the lights on for a minute after engine turn off.
c) Dome light flashes - CTM controls the dome light to provide courtesy
lighting for entrance and exit.
d) Dash illumination - This I'm not sure that the CTM is involved in, but it's
part of the headlight on/off circuit, so it could be a side effect of the
headlights flashing.
e) The "Service 4WD" lamp on the dash never lights. This could be a burned out
bulb, or a fault on the board for the instrument panel.
It seems like the CTM is having a problem and is resetting a few times.
Other than obtaining access to a DRBIII, is there a way to test or check the
CTM? I'm thinking that while I'm hunting the junkyards for a TCCM, I may want
to grab the CTM as well. It'd be a lot cheaper to replace the CTM than to buy
a DRBIII.
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