2005 Chrysler PT Cruiser Codes P0325 & P0340

P0325 - Knock Sensor 1 Circuit Malfunction (Bank 1 or Single Sensor)
P0340 - Camshaft Position Sensor Circuit Malfunction

First of all, this is an "interference" engine. Get that timing belt replaced now. If it breaks the open valves will be hit and bent by the pistons as they coast to a stop. That will turn a maintenance repair into an expensive valve job. Chrysler has some safety margin built in to their mileage recommendations, but years ago Honda recommended their timing belts be replaced at 75,000 miles and they commonly broke at 65,000 miles resulting in a lot of expensive repair bills.

If the engine runs okay at times with normal power, the timing belt has not jumped a tooth yet. You will definitely notice the lack of power when that happens. When it does, it will not magically jump back into proper time by itself so it won't run well at times. It will always run poorly. Also, if it jumps one tooth, that will be detected by the Engine Computer. It will set a fault code for "crank and cam sync", and turn on the Check Engine light to tell you. If the belt jumps two teeth the computer will shut the engine down to protect the valves. If it jumps three teeth the valves will be bent.

I wouldn't concern myself with code 325 right now. Code 340 is the clue. The camshaft position sensor and the crankshaft position sensor both need to send signals to the Engine Computer all the time the engine is running. Code 340 isn't specific as to the type of problem the computer detected, and there's only perhaps a 50 percent chance the sensor is actually the culprit. It's more likely there is an intermittent problem caused by the wiring and connector terminals, but regardless, the code only indicates the circuit that needs further diagnosis. Your mechanic will likely connect a scanner to view live sensor data on a test drive to see what is happening when the problems occur.

I'm a cheapskate when I work on my stuff but all of my Chrysler products have non-interference engines, so this is a case of do as I say, not as I do. It is standard practice to replace the water pump along with the timing belt and a conscientious mechanic will quote the repair estimate including the pump if he has your best interest at heart. It generally takes an additional half hour or less to replace the water pump at the same time while everything else it apart. If that isn't done, and the pump starts to leak or gets noisy a few months later, you will be paying for the same repair again, plus, the sloppy pump bearings could destroy the new timing belt.

There is also some type of tensioning device that should be replaced to insure the quality of the repair. Some suppliers offer complete kits that include the belt, water pump, and any idler pulleys or tensioners. Those kits leave nothing to chance.