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FCM/Radio diagnosis

  #1  
Old 11-07-2009, 04:43 PM
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Default FCM/Radio diagnosis

Hi, I'm hoping someone can help-- my 01 T&C's speakers are completely dead and after some diagnosis, I've narrowed it down to the fact that the Name Brand Speaker relay in the IPM is not activating. If I jump the relay slots with a wire, the speakers work fine. I've swapped the relay with a known good one, so that's not the problem. The relay just is not coming on when it's supposed to. DRBIII is showing no codes in the FCM and, unfortunately, does not have any PIDs for the NBS relay that would give me any info about what the FCM is "seeing".

Any ideas for further diagnosis before I condemn the IPM/FCM? Your help will be very much appreciated as we have a long trip coming up.
 
  #2  
Old 11-07-2009, 06:59 PM
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If you have a wiring diagram, and remove the radio, you just might find the problem at the back of the radio.
 
  #3  
Old 11-08-2009, 02:05 AM
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Sorry Rick but this does not make sense. If you jump the slots with a wire and it works, then the new relay should fix it unless the new relay is bad. How many contacts are we talking here on this relay?
 
  #4  
Old 11-08-2009, 05:18 AM
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It's a standard mini relay with 5 contacts. I swapped in another relay from the vehicle that I know is working. The fact that a replacement relay doesn't work is leading me toward thinking that the driver in the front control module is bad. Can you think of anything else to check?

22chrysler-- the speakers work when I jumper the relay slots, so it seems that there's no problem at the radio itself.
 
  #5  
Old 11-08-2009, 07:34 AM
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it's quite appearant that you guys don't understand how a relay works. From the jumper description, the main power is good and the wires to the speaker amps is good, so that means the high current side is working fine. so the problem lies in the control side of the relay. A wiring diagram will be of tremendous help in identifying the power and ground to the control side. Once you determine these components of wiring, you should easily figure out where the problem is.

power to the relay for both main power and control power both come from fuse 14 which is 15amp. Seems the these radios changed a lot from 2000 back to the first "name brand" system used in everthing where there was a dark green wire grounded to the radio. I'll bet that you'll have 2 powered terminals in relay socket. so where lies the problem is in the ground side to energize the magnetic coil that activates the relay. You could have a wiring problem to the Front Control Module or a Module failure.

AGAIN... GET A SCHEMATIC
 
  #6  
Old 11-08-2009, 01:29 PM
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So if the fuse controls both sides then he needs to determine that he is getting power on the control side? It sounds like he is jumping the load side? As stated perhaps the radio is not energizing the control side? I have the diagrams. I will see if I can look at them if I get a chance. that stuff can take a while to view, especailly in PDF format. Oh.. I just checked.. I only have the 05 manual.
 
  #7  
Old 11-08-2009, 02:50 PM
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I have shop key and FSM's. Yes, the same fuse provides power to the relay power circuit and control/magnet side. the activation for the control side is provided by the front control module
 
  #8  
Old 11-10-2009, 02:18 PM
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I understand how relays work the question is more about how the FCM works. I have the diagrams and have been using them through this process-- they led me back to the relay when I determined no power was getting to the speakers. There is power at the appropriate sockets for the relay-- the fuse is fine- so the FCM is not activating the relay. That would mean either that the FCM is not getting the necessary data input to cause it to activate the NBS relay or the control circuit (technically called the "driver") for the relay is broken. I was hoping someone knew more about the FCM's software and could tell me if there is a way to check whether the FCM is getting the input it needs to get it to turn on the NBS relay-- I thought it may need an input over the PCI bus from the radio, but looking at the factory service manual, it appears that this is not one of the FCM's data inputs.

Presumably the FCM is programmed to turn on the NBS relay whenever the ignition is in the run/accessory positions. I guess this all means there's nothing else to test-- either the internal wiring in the fuse block is bad (doubtful) or the FCM has a bad driver.

I've thought this through a bit and since the FCM is about $250, I may try to solder a permanent jumper into the fuse block so that the FCM's accessory relay driver will also activate the NBS relay. That will make the FCM do the same thing it did before-- energize the NBS relay when the ignition is in the run/accessory position. If that overloads the FCM's circuitry, I'll just have to replace the FCM.
 
  #9  
Old 11-10-2009, 05:37 PM
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"I thought it may need an input over the PCI bus from the radio," It looks like it works this way on the 05's.


make sure to zoom

http://picasaweb.google.com/lh/photo...eat=directlink
 

Last edited by mrfixit454; 11-10-2009 at 05:41 PM.
  #10  
Old 11-11-2009, 06:47 AM
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Originally Posted by mrfixit454 View Post
"I thought it may need an input over the PCI bus from the radio," It looks like it works this way on the 05's.


make sure to zoom

http://picasaweb.google.com/lh/photo...eat=directlink
Thanks for posting this-- the 01 manual doesn't have a diagram showing a direct link between the radio and the FCM through the PCI bus. If you go to the diagnostic port section, you can see the link though, so they are tied together in the 01's.

Could you take a look at the written description of the FCM in your manual? It's section 8E-something in my 01 manual-- there should be a list of "inputs" that the FCM receives and responds to. I'm curious if radio on/off status is one of the inputs for an 05.
 

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