So, the BCM is dead?

1997, Dodge Intrepid. 130K miles.

The currently situations are:
(just in case you want to see it yourself, I made a short video of the
problem, see here:
http://www2.uic.edu/~kzhao3/car02.htm
)

1) The car can start and drive, although if I put it to P, the sound
from the engine seems to indicate that the engine sometimes goes
faster sometimes goes slower.

2) The wiper will start to work at the same time the car is powered
on, and will not stop.

3) The engine speed meter and the car speed meter give random
readings. The engine temperature meter has no reading. The gas meter
has no reading (sometimes will have some reading).

4) Turning signals seem not work too.

5) The light inside the car is not working (usually when I open the
car door, it should light up and dim slowly).

6) The power door lock does not work.

I have done the following checks:

1) I have taken off and checked the multi function switch (the one for
the turning lights, etc) and the headlights switch, they seem OK
according to the manual. And if I start the car without the above two
switches, all the problems still there.

2) I have confirmed that the terminals of the battery are clean and
the cables to them are good. Also, the negative terminal is connected
to the car's frame properly (as suggested by a friend).

3) All the fuses are OK.

So, I think the BCM is dead. How is your guys' idea?

By the way, if I take out the BCM, how can I tell whether it is OK or
not? (for example, by using a multi meter, etc)

Thanks a lot.

 

Well, you certainly have some electrical gremlins, and they could be
related to the BCM. This is going to be a tricky one for a DIYer to diagnose properly,
although I believe its possible if you ask yourself the right questions
and proceed methodically. It would be extremely helpful to have a copy
of the factory service manual and body diagnostics manual as well.

One common thing to check before condemning the BCM are its ground
connections. You may also have one or more electrical shorts in the
wiring harness causing issues such as this.

Did all of these symptoms come on suddenly? Was the car involved in any
flooding, an accident, or anything else unusual? Is the battery at full
strength? Was the car jumpstarted any time recently? Was there any
work done on the charging system? Has there been any work done on the
car at all recently?

It's interesting, I think, that the problem manifests itself when the
engine is running. How about if you just switch the key to the 'run'
position without starting it? Same things?

Will the car display its dashboard flash codes using the
key-on-key-off-key-on-key-off-key-on procedure? (Google this newsgroup
if you need more description)

--Geoff

 

Thanks for the entertaining video, though you need to rename your windows
file to .wmv.

As for your problem its going to be difficult to diagnose without access to
the CCD bus via a DRB. You can however remove the BCM and carefully inspect
the PCB for all the solder joints looking for broken or cracked solder,
doing continuity checks and wiggling the solder ends with your multimeter
probe. I find that most modern cars are using some lame ass solder that
seems to break after about 5-10 years and can be a real pita to track down.
Ive solved a few problems with printed circuit boards by simply reflowing
the solder on as many points as possible/practical. There was a problem a
while back with caravan BCM's having bad transistors on the CCD bus you
might want to check that out for shits and giggles.

Hope you find out what the problem is without having to mortgage your
house.....