Chrysler Repair: 2003 Caravan quit running and wont start., head gasket leak, exhaust gas recirculation valve

Question
My wife was driving our 2003 4 cyl. Caravan and it suddenly quit running after she pulled onto the highway. It hasn't started since. It turns over, but sounds different, like it is struggling. Freshly charged battery. My main concern is the white smoke coming out of the air fliter housing when I turn it over. Blocked catalytic converter? Ran fine until that point. The only code I get via the on-off-on method is P1684.  

Answer
Hi Eric,
That white smoke is certainly suspicious. Does it smell like unburnt/burnt gasoline or does it smell like antifreeze? The former would indicate some sort of a blockage like you suggested in the exhaust pathway. The latter would be indicative of a head gasket leak that is allowing coolant to leak into a combustion chamber which when you try the starter will resist being compressed (causing struggling, even lock-up). The absence of codes removes many other possibilities. So take a smell to say what it is like.
Another possibility (with no codes) is that the exhaust gas recirculation valve is stuck open which will lean out the mixture and prevent starting. It is located at the far rear end of the engine on the firewall side. Look for a flange area between the round vacuum top and the body of the valve mounted in the small exhaust pipe. Notice a rod inside the flange that has a slot around its circumference.
That is the valve stem. Move the stem by means of a screwdriver inserted into the slot, back and forth against spring-action in one direction. The spring should move the stem to a dead stop, closed. If it seems sticky in its action, spray some WD-40 on the valve stem where it enters the valve body. Then work it back and forth to free up the action. Then try to start it.
Roland
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