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Q: My car stalls arbitrarily and with no warning and is getting progressively harder to start.

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I bought a used 99 Dodge Intrepid a couple months ago. Soon after, it stalled in the hwy at 65 mph with no warning. The tach simply dropped to zero. Other than the cruise control light coming on, nothing was different. I pulled off with my flashers and it started right back up. The next night, it happened again- took a few minutes to start back up. It has since progressively become harder and harder to start. The other night, it wouldn't start for a few hours. So, the online "research" I've done overwhelmingly points to the camshaft and/or crankshaft position sensors as well as a possible cat converter problem. I got 3 trouble codes from the odometer 1. P1684: battery disconnected within the last 50 starts (which I had definitely not done) 2. P0420- Catalyst system efficiency below threshold (bank1) 3. P0432--Main catalyst system efficiency below threshold (bank2). I keep hearing that I should start with the Camshaft position sensor, as its the easier one to fix

My car has 217000 miles.
My car has an automatic transmission.

Hello and thank you for contacting YourMechanic. The code P1684 means that there was a battery disconnect from a sensor to the computer, or in other words, a sensor has lost communication with the computer. The code P0420 usually means that the catalyst converter is not functioning correctly. The code P0432 means that the catalyst converter could not functioning or there could be a problem with the fuel to air mixture.

Most of the time when these codes are present, there is a problem with the fuel mixture and causing the catalyst converter to work harder. The camshaft sensor will cause an engine to have a no start situation along with an incorrect fuel ratio. I recommend replacing the crankshaft sensor, replacing the camshaft sensor, and cleaning the MAF (Mass Air Flow) sensor. This should keep your vehicle in top shape and no issues. If the problem continues, have a professional mechanic, like one from YourMechanic diagnose the stalling issue and proceed with repairs.

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