Expert: Roland Finston - 8/24/2011

Question
QUESTION: I have a 1999 Chrysler Concorde that has plenty of fuel to the rail but it does now have any spark at all what could that possibly be please help me i am at a loss on this car right now.

ANSWER: Hi Richie,
The best way to find out is to use the self-diagnostic capability on board using the ignition key:"on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. Then watch the odometer window of the cluster to see the mileage reading change to show a 4-digit number preceded by a P. Let me know the number(s) and we'll go from there. Tell me which engine (L) you have.
Roland

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QUESTION: the code number is a p1684 and i have a 3.2L v6 in this car

Answer
Hi Richie,
The 1684 is saying that the battery connection to the pcm was disconnected sometime in the past 50-100 key on-off cycles. That happens whenever you disconnect the battery so it doesn't indicate a problem unless that disconnection recently is not the case.
Also, the computer would generally notice a problem with the engine rotational sensors or the primary circuit to the individual plug coils (which would kill the spark signal) and give us a code. So the only thing I can suggest is that the capacitor that filters out noise (there are two, one for each bank of cylinders) that is mounted on the cylinder head is leaking voltage to ground so that the 12V needed by the coils is not there at full strength. So verify that you have 12v on the dark green/light green wire at both capacitors, or at a coil plug on both banks of cylinders while you are cranking it over. Fuse S (20 amp) in the box in the engine compartment is also needed to put out the 12v for the spark coils, so check that as well.
Roland