Chrysler Repair/1994 Chrysler LHS: BCM
QUESTION: Hi again Roland,
All of the gauges on my 94 LHS has stopped working and I have traced all the wiring and there are no exposed places for the wiring to short out. Fuse # 13 and #14 were blown but I believe that the issue is the BCM. I have been looking in the junk yards for one and at one of them, the guy behind the counter said that I have to have one from a 94 model. One from a 95,96 or 97 will not work. Is this correct. Also, after the car sat for a few days, everything started working again when I started the car to move it out of the driveway. When I went to move it back the next day, nothing works again and the car will not start. It tries but does not catch. Will the BCM keep the motor from starting?
Thanks for your help.
ANSWER: Hi Mar,
Fuse #13 is the ignition off draw fuse that powers courtesy lights and power door locks. Fuse #14 powers parts of the BCM at pin 13 of the bone colored plug at the bcm when the ignition switch is in the run position. So check out that power supply to the bcm. The gauge readings are digital and come from the bcm to the cluster and are pins 10 and 9 of the black plug at the cluster which come from pins 12 and 7 of the body computer gray plug, respectively. So check those out as well. The odometer and speedo readings get to the cluster on the other digital bus from the pcm on pins 2 and 3 of the black plug at the cluster, if those are not working.
The bcm shouldn't prevent the car from starting. Do the ignition switch routine to get a fault code. Turn it "on-off-on-off-on and leave on" in 5 seconds or less elapsed time. Then watch the check engine light, which remains "on", to see it begin to flash, pause, flash, etc. Count the number of flashes before each pause, then repeat for accuracy. Tell me the counts in order of appearance and we'll go from there.
Please read the PS (below) and respond to it.
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QUESTION: Thanks Roland. I will check it out and let you know if it is pulling any codes. If I finds another BCM, does it have to be from a 94 only or can I use a 95 - 97?
ANSWER: Hi Mar,
The wiring of the '95-'97 bcm is likely the same as the '94, but I have no info on whether the functioning of it would be identical. A dealer parts counter could tell you if the part numbers were identical, and if not then I would avoid anything but a '94.
Thanks for the rating/nomination and kind remarks.
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QUESTION: Hi Roland,
Not pulling any codes with the key switch. Actually it is not even giving me the 55 code for no codes. What is new is that when I put the key in the ignition switch, the dinger and the interior lights will do a cycle of four flashes and dings, pause, then do it again as long as the key is in the switch. On checking the pins in the BCM, I don't see any numbering on the pins so are the from left to right and what is the best way to test them? Or should I be checking the wires in the plug and what is the best way to check them?
So you are not getting any flashing of the check engine light at all? The dinger and interior light flashing may have to do with alerting you that you have the key in the ignition AND that the driver side door is open, which is probably a normal alert. The lack of any functioning from the fault code test may be due to not completing the key cycling in less than 5 seconds, or if that is not the case, then I would wonder about there being a fuse that powers the pcm not being patent. I assume the check engine light does come 'on'.
Until you get a fault code, at least check to see if the fuel pump hums for a second when you turn the key to the 'run' position. And also check for spark at one of the plugs
The bcm pins are numbered on its plugs, so use that as your guide. In any event you would want to test for wire continuity between the plug's pins and the similar pins at the cluster plug, rather than doing any reading of the sockets for those pins at the two units. Use an ohmmeter or continuity tester.
Another possible explanation for the off and on problem with the gauges is that the bcm itself has gotten wet at the top side where the plugs and sockets are located. Any water leaking in from around the windshield can drip down directly on the top of the bcm and cause miscellaneous 'gremlins'. Were that the case, you can use some electronic circuit cleaner that comes in spray can and apply that to the top of the bcm. When it evaporates it removes any moisture that might be in the socket and on the plug pin.
By the way you are welcome to do another rating/nomination of all my answers.